1 or 2 subs?
Robert McFee
sound significantly better with 2 subwoofers so that that the low bass
is in stereo as opposed to my current setup in which all the bass is
summed through one sub? Thanks! ------- Rob McFee
PSiu89449
<rmc...@nbnet.nb.ca> writes:
This depends on your existing setup. It can range from very minor to
significant improvements.
If you have full range speakers to begin with and you are crossing
your single subwoofer at very low frequences, such as <60Hz, any
improvement on 2 subs over 1 will be very minor. But this also depends
on the quality of your sub. In this case, using 2 subs will afford you
slightly wider dynamic range and lower distortion. Stereo information
at these low frequency range is very hard to preceive. To some,
detection may be nearly impossible.
If you have mini-monitors which requires you to cross the sub above
>90Hz, you will absolutely hear an improvement with stereo subs. You
will be surprise how much low mid information you can hear, pending on
low pass slope, with subs crossed above 90Hz. At these frequences, you
will be able to detect different signals coming from your left and
right subwoofers. Henceforth, placement of subs here should take
stereo imaging into consideration.
Between 60 to 90 Hz, stereo subs become a mood point. But keep in mind
that one subwoofer will excite one set of room resonance while using
two will excite two. If properly placed, the two will compliment each
other thus randomizing these resonance. Unfortunately, this can often
be a double edge sword. Phase and arrival time can also be very tricky
with multiple subs. Take this from a guy who have seven sets of subs
under one roof. Five of them are stereo pairs and one pair being
build-in.
Best Regards
Paul Siu
David Clark
come out mono. I think you need to consider your room size when
deciding on 1 or 2 subs. Unless your room is very large 1 good sub
should do.
Robert McFee wrote in message <6scdst$t0d$1...@agate.berkeley.edu>...
Nousaine
of which I agree with. Here's a small embellishment:
<<<Between 60 to 90 Hz, stereo subs become a mood point. But keep in
mind that one subwoofer will excite one set of room resonance while
using two will excite two. If properly placed, the two will
compliment each other thus randomizing these resonance. >>>
I would say that under 100 Hz 'stereo' is an oxymoron in
reproduction. On the other hand, a second subwoofer doesn't excite
two sets of room resonances (standing waves.) These are a function on
the room and its dimensions. The frequencies and number of modes is
fixed for a given room. The problem is not exciting enough of them to
assure smooth, evenn distribution of energy in the room.
The best solution to the room resonances problem is to excite as many
as you can by placing a single or multiple subwoofers in a corner.
Scattering them aroudn the room will 'unexcite' or stack some modes
at a given listening position causing uneven bass response.
As Paul says this is a two edged sword....a second subwoofer will
help generate adequate SPL at low frequencies but if used as a
'stereo' pair usually causes uneven bass response.
PSiu89449
writes:
>I would say that under 100 Hz 'stereo' is an oxymoron in
>reproduction. On the other hand, a second subwoofer doesn't excite
>two sets of room resonances (standing waves.) These are a function on
>the room and its dimensions. The frequencies and number of modes is
>fixed for a given room. The problem is not exciting enough of them to
>assure smooth, evenn distribution of energy in the room.
For the lack of a better term, Mr. Nousaine is more precise in his
description.
Based on personal experience and a graphical study done recently in
Speaker Builder magazine three issue's ago, placing one subwoffer in
a room will cause a set of nulls and peaks. The location of this sub
will dictate this pattern throughout a room. If we move this
subwoofer to another location, such as across this room, a different
set of nulls and peaks will appear. Henceforth, placing two subs in
the same location will still excite one set while placing them in
totally different location will generate two. The effect of these
nulls and peaks sets will cancel or compound itself making prediction
of smooth overall response tricky at best.
Unfortunately, there is no set of rules that accurately predict any
given room situation. My personal recommendation, and only when
practical, is to use multiple sets of subs to "excite enough of them
to assure smooth even distribution of energy in the room." But only
with careful tunning, listening, and accurate measurements will we be
able to obtain good results. However, there is a more elegant
solution. Having done this myself before, I also recommend placing a
mono subwoofer immediately behind the listening position or a pair of
stereo subs immediately flanking the same. This extreme close field
placement will mostly dominate any uneven room related resonance
resulting in a flat frequence response. But it can only be as flat as
ones subwoofer.
David Clark" <dmc_c...@email.msn.com> writes:
>Bass is mono not stereo, so wether you have 1 sub or 2 the bass will
>come out mono. I think you need to consider your room size when
>deciding on 1 or 2 subs. Unless your room is very large 1 good sub
>should do.
The recommendation based on room size is very valid, but bass
information isn't necessary mono. With analog recovery systems, such
as Lp's, most if not all bass information is recorded in mono due to
this medium's limitation. But almost all digital recordings can and
do reproduce stereo bass information. But again, as frequency
decrease with their respective increase in wave lenght, stereo
information in low bass does approximate mono. However, there is
still a small degree of preceivable stereo information above 60Hz.
Arguably, phase information plays an important role in the preceived
accuracy of bass reproduction.
Best Regard
Paul Siu
Wendell Narrod
>
> Bass is mono not stereo, so wether you have 1 sub or 2 the bass will
> come out mono. I think you need to consider your room size when
> deciding on 1 or 2 subs. Unless your room is very large 1 good sub
> should do.
I'm not sure this is entirely correct. Certainly the bass was usually
summed on vinyl to improve trackability. I believe with CDs and new
recordings that the bass is in stereo. I use Audio Physic Virgos and
a pair of Vandersteen subs. The improvement in soundstaging, detail
and transparency is readily apparent with two subs versus one. I also
thought that the bass is not summed on new audiophile vinyl. Then
again, perhaps I am totally wrong.
--
Wendell Narrod
nar...@earthlink.net
wna...@hotmail.com
909-949-4581
jwd
>
> Bass is mono not stereo, so wether you have 1 sub or 2 the bass will
> come out mono. I think you need to consider your room size when
> deciding on 1 or 2 subs. Unless your room is very large 1 good sub
> should do.
I don't understand. How is Bass mono. When I listen to Bill Evans
Trio at Shelly's Manne-Hole (xrcd) Chuck Israels' bass is standing
just a bit left of my left speaker. How is bass any more mono then
any other instrument? I realize that the subs have one channel so my
real question is how does a sub in the right hand corner of the room
maintain the pinpoint accuracy of the bass on the far left side of
the of the room.
Thanks
jwd
jj, curmudgeon and tiring philalethist
PSiu89449 <psiu...@aol.com> wrote:
>In article <6seh1p$r...@news01.aud.alcatel.com>, nous...@aol.com (Nousaine)
>writes:
>>I would say that under 100 Hz 'stereo' is an oxymoron in
>>reproduction. On the other hand, a second subwoofer doesn't excite
>>two sets of room resonances (standing waves.) These are a function on
>>the room and its dimensions. The frequencies and number of modes is
>>fixed for a given room. The problem is not exciting enough of them to
>>assure smooth, evenn distribution of energy in the room.
I must somewhat differ in the subject of 'under 100 Hz stereo'.
A sense of spaciousness has been demonstrated when out-of-phase
signals occur at low frequencies. Their amplitude is quite low
at the listener (no kidding!) but the result is much like the effects
one gets in a VERY large venue, hence the likely source of the effect.
This effect is hard (cough) to reproduce with one subwoofer.
--
Copyright j...@research.att.com 1998, all rights reserved, except transmission
by USENET and like facilities granted. This notice must be included. Any
use by a provider charging in any way for the IP represented in and by this
article and any inclusion in print or other media are specifically prohibited.
Jes Sherborne
>I don't understand. How is Bass mono. When I listen to Bill Evans
>Trio at Shelly's Manne-Hole (xrcd) Chuck Israels' bass is standing
>just a bit left of my left speaker. How is bass any more mono then
>any other instrument?
When people refer to bass being nondirectional (or mono or whatever),
they usually mean that people can't generally get location cues from
audio frequencies under about 60 Hz (i.e., we can't tell where the
sound is coming from). Since an acoustic bass actually makes sound
over a pretty wide chunk of the audible frequency spectrum, we can
perceive its location.
--Jes
Nousaine
<<<I don't understand. How is Bass mono. When I listen to Bill Evans Trio at
Shelly's Manne-Hole (xrcd) Chuck Israels' bass is standing just a bit left of
my left speaker. How is bass any more mono then any other instrument? I realize
that the subs have one channel so my real question is how does a sub in the
right hand corner of the room
maintain the pinpoint accuracy of the bass on the far left side of the of the
room.>>>
This is a really good question. The answer is that even an acoustic
bass has significant higher frequency content. We localize sound with
higher frequency spectrum. When a train approaches the station we
cannot tell which direction it comes from unless 1) we already know
which direction it is supposed to come from or 2) we get higher
frequency information that gives us direction.
In your example the higher frequency content gives you location and
the low stuff gives you feel and body. Otherwise you would have to
move your woofer around for every recording.
Curtis Leeds
>
> Bass is mono not stereo, so wether you have 1 sub or 2 the bass will
> come out mono.
This is one canard that is due to be put to rest. There can
be significant directional information (even from LPs,
although many of them do have summed bass) in the low
frequencies. This is not difficult to hear on a good full
range system.
Although its bass is neither r-e-a-l-l-y low nor accurate,
James Taylor's "Fire And Rain" has a lot of stereo
information on it. With a mono subwoofer you'd miss half the
power of that track.
--
***************************************************
cle...@idt.net "I stood unwound beneath the skies
And clouds unbound by laws.
The cryin' rain like a trumpet sang
And asked for no applause." (Bob Dylan)
***************************************************
Keith A. Lahteine
This has a lot to do with your, possibly, benefiting with two rather
than one sub If you're crossing to the sub from about 100Hz. there
will be almost no left and right component . When your dealing with
such low frequencies separation all but vanishes, both, electricaly
and mechanicaly . If you're just trying to fill a larger space then
using two subs may be the way to do it but trying to impart a stereo
effect is, probably, a futile goal .
Sincerely : Keith A. Lahteine
PSiu89449
<jsher...@earthlink.net> writes:
>When people refer to bass being nondirectional (or mono or whatever),
>they usually mean that people can't generally get location cues from
>audio frequencies under about 60 Hz (i.e., we can't tell where the
>sound is coming from). Since an acoustic bass actually makes sound
>over a pretty wide chunk of the audible frequency spectrum, we can
>perceive its location.
Here is a useful experiment. Low pass your sub at 90 - 100Hz and feed
it some acoustic bass material without your main or satellite
speakers. Regardless of the low pass slope, try to isolate the source
of the bass. Providing if you have the right equipment, now gradually
lower the x'over point. There will come a point where it will be
extremely difficult, if not impossible, to hear the source location.
With 4th order or higher x'over, the audible point will be higher. My
best guess is somewhere between 60 to 90Hz.
This should be the starting point to determine at what frequency your
sub will become location audible. If your prime use of sub is under
this frequency, you should get by with one sub. If sub use is above
this frequency, you should strongly consider stereo sub.
Best Regard
Paul Siu
We3millerz
>be significant directional information (even from LPs,
>although many of them do have summed bass) in the low
>frequencies. This is not difficult to hear on a good full
>range system.
you may be confusing ordinary robust bass with the low bass
frequencies associated with subs. if you are betting that you can
localize frequencies below about 80 Hz, whose harmonic overtones above
that freq have been filtered out, you stand to lose a lot of money.
you need to lower the crossover on your sub and perhaps use a steeper
slope on the low pass. The length of waves alone for low bass should
indicate to you how problematic it would be to localize the sounds.
PSiu89449
writes:
>you may be confusing ordinary robust bass with the low bass
>frequencies associated with subs. if you are betting that you can
>localize frequencies below about 80 Hz, whose harmonic overtones above
>that freq have been filtered out, you stand to lose a lot of money.
I wouldn't bet a single dollar against this theory. I don't want to
loose. It is only with low order lowpass at 80 Hz or even 60 Hz can I
begin to detect any directional clues with subwoofer driven alone due
to harmonic overtones and phase influence.
>you need to lower the crossover on your sub and perhaps use a steeper
>slope on the low pass. The length of waves alone for low bass should
>indicate to you how problematic it would be to localize the sounds.
There can be no argument here especially in the view that we take low
bass reproduction as an isolated sound source. This further supports
my previous postings regarding the difficulty in identifying
directional clues of low bass; analog or digital alike.
Now..... Lets go through a small exercise that will demonstrate this
point. Consider for a moment that we are to connect a pair of full
range speakers in opposite polarity to each other. The sound of this
speaker set will sound totally out of phase. We will not be able to
identify any image or staging. If we can, hypothetically, look at
frequencies as an individual subset, we will see that the most
important midrange is the predominant range through which we can
identify this phase problem. At the extreme ends of this sprectrum,
our aural preception indicates that the highs will not float at some
distance between speakers but glued to the the sound source; in this
case the tweeters. The deep bass will be extremely attenuated due to
large scale cancellation.
Lets look at this phenomenon with a sliding frequency window. As we
slide our preception window down from the midrange, the phasiness of
this sound will gradually decrease along the the preceived
volume. Between 500 to 100Hz, the phase problem will remain
dominant. Between 80 to 100Hz, we should still preceive some phase
problems and not until lower frequencies will we preceive it as a
cancellation effect. It is exactly at these transition windows that
one can argue about the audibility of directional clues.
With typical lowpass crossover that governs our subwoofers, there are
still enough information above 80Hz to impact upon image quality via
phase preception. Not unless we insert a brickwall type lowpass filter
at these frequencies, my recommendation is to consider lower lowpass
down to 60Hz in order to minimize its effect on imaging and staging
quality. Henceforth, between 60 to 80Hz, stereo subwoofers become a
mood point.
Best Regards
Paul Siu
Curtis Leeds
> >This is one canard that is due to be put to rest. There can
> >be significant directional information (even from LPs,
> >although many of them do have summed bass) in the low
> >frequencies. This is not difficult to hear on a good full
> >range system.
...and We3millerz answers:
> you may be confusing ordinary robust bass with the low bass
> frequencies associated with subs. if you are betting that you can
> localize frequencies below about 80 Hz, whose harmonic overtones above
> that freq have been filtered out, you stand to lose a lot of money.
Well, I haven't made the bet - but it would be a safe one.
Many people who espouse this "all bass is mono" theory have
never experimented to test the belief.
> you need to lower the crossover on your sub and perhaps use a steeper
> slope on the low pass. The length of waves alone for low bass should
> indicate to you how problematic it would be to localize the sounds.
It's simply mistaken to believe that all bass is essentially
mono. I've experimented with various woofer locations and
configurations (I don't use subs - instead, I use a
full-range speaker system with separate woofer towers), and
there's no question that in my room and with my equipment,
there's a big difference between mono and stereo bass.
Nousaine
<<<Well, I haven't made the bet - but it would be a safe one. Many people who
espouse this "all bass is mono" theory have never experimented to test the
belief.>>>
Well I have. I searched to find programs with out-of-phase
information at subwoofer frequencies (no small feat...how are you
going to get 'stereo' at very low frequencies with the wavelengths
involved...and even if you get it recorded how can you hear it when
your ears are only 8-inches apart.) Then I placed a pair of identical
subwoofers under a pair of left and right satellite speakers. Blind
listeners were unable to tell when the source was switched between
stereo and mono with an 80 or 100 Hz crossover frequency.
<<<It's simply mistaken to believe that all bass is essentially mono. I've
experimented with various woofer locations and configurations (I don't use subs
- instead, I use a full-range speaker system with separate woofer towers), and
there's no question that in my room and with my equipment, there's a big
difference between mono and stereo bass.>>
It is true that differing locations bring different 'bass'
presentation due to standing waves. But again there are precious few
sounds that have only low frequency sound. The higher frequency
content gives all the location and spaciousness cues on modern
recordings.
Curtis Leeds
>... I searched to find programs with out-of-phase
> information at subwoofer frequencies (no small feat...how are you
> going to get 'stereo' at very low frequencies with the wavelengths
> involved...
This is begging the question, of course. You're saying "all
low bass is mono so it is difficult to find recordings with
directional bass". But there *are* recordings with
stereophonic bass.
>...and even if you get it recorded how can you hear it when
> your ears are only 8-inches apart.)
Stereo in the LF is heard the same way as stereo in the HF.
And remember that the difference between the channels need
only be but a few dB in order to achieve a definite stereo
effect.
> Then I placed a pair of identical
> subwoofers under a pair of left and right satellite speakers. Blind
> listeners were unable to tell when the source was switched between
> stereo and mono with an 80 or 100 Hz crossover frequency.
I won't dispute the results you obtained, but can only note
that it conflicts with the results that I attained in my
room. Given the large effect that the room can have on LF, I
think you're a bit hasty to conclude that your results would
apply to all systems in all rooms.
> It is true that differing locations bring different 'bass'
> presentation due to standing waves.
Big time!
>... The higher frequency
> content gives all the location and spaciousness cues on modern
> recordings.
What does the age of the recording have to do with the
directionality of the LF?
Nousaine
>... I searched to find programs with out-of-phase information at subwoofer
frequencies (no small feat...how are you
going to get 'stereo' at very low frequencies with the wavelengths
involved...<<
<<<This is begging the question, of course. You're saying "all low bass is mono
so it is difficult to find recordings with directional bass". But there *are*
recordings with
stereophonic bass.>>
Sure but they are all studio recordings where it has been added
intentionally.
>>...and even if you get it recorded how can you hear it when> your ears are
only 8-inches apart.)<<
<<<Stereo in the LF is heard the same way as stereo in the HF. And remember
that the difference between the channels need
only be but a few dB in order to achieve a definite stereo effect.>>>
Cmon you are begging the question. With a 20 foot wavelength how do
you hear 'stereo' when your ears are less than a foot apart?
> Then I placed a pair of identical subwoofers under a pair of left and right
satellite speakers. Blind listeners were unable to tell when the source was
switched between stereo and mono with an 80 or 100 Hz crossover frequency.<
<<<I won't dispute the results you obtained, but can only note that it
conflicts with the results that I attained in my room. Given the large effect
that the room can have on LF, I
think you're a bit hasty to conclude that your results would apply to all
systems in all rooms.>>>
So why would yours apply anywhere but your room then? Were any of your
results doen with controlled listening? Not to be argumentative but I
used second party listeners to be sure that my initial observations
wouldn't color the results. My hypothesis was that some type of
effect would be noticeable with recordings confirmed to have stereo
content at low frequencies.
>... The higher frequency content gives all the location and spaciousness cues
on modern
recordings.<
<<< What does the age of the recording have to do with the directionality of
the LF?>>
Nothing except that later recordings are the only ones with any
out-of-phase content between channels.
jj, curmudgeon and tiring philalethist
Nousaine <nous...@aol.com> wrote:
>Sure but they are all studio recordings where it has been added
>intentionally.
I've got a recording I just made in my basement that was made on-site
that has stereophonic bass, Tom.
Not ALL of them are added "intentionally". Now, this "stereophonic"
amounts to about a .8 millisecond (at most) change in phase. This
isn't much, but you know, you can hear it rather nicely.
Curtis Leeds
> Cmon you are begging the question. With a 20 foot wavelength how do
> you hear 'stereo' when your ears are less than a foot apart?
Good question. I don't claim to have the answer.
> So why would yours apply anywhere but your room then?
The premise here was: all bass is mono, hence there is no
benefit from stereo bass playback. We need to disprove this
only once to show the claim false. If the benefit of stereo
bass is not evident in your room, that doesn't mean that it
isn't evident in other rooms, with different equipment, with
different listeners.
Nousaine
<<<I've got a recording I just made in my basement that was made on-site that
has stereophonic bass, Tom.
Not ALL of them are added "intentionally". Now, this "stereophonic" amounts to
about a .8 millisecond (at most) change in phase. This
isn't much, but you know, you can hear it rather nicely.
>>>
Okay I give, what is on the recording? Can you hear it with a slow ramp and a
100 hz low pass filter?
Sascha Erni, lc
> Cmon you are begging the question. With a 20 foot wavelength how do
> you hear 'stereo' when your ears are less than a foot apart?
As you do with headphones -- differences in pressure. The human ear
has quite a few very interesting mechanisms to orientate itself in an
acoustic field; phase is only one of them.
But it is a psychoacoustic fact that humans are not able to pin down
locations solely with frequencies <60Hz. Not accurately, that is (and
at something like 45Hz not at all).
l*Greetings*c
jj, curmudgeon and tiring philalethist
Nousaine <nous...@aol.com> wrote:
>Okay I give, what is on the recording? Can you hear it with a slow ramp and a
>100 hz low pass filter?
An off-axis tuba, playing the tuba part of transcripted show tunes.
There are acutally several different delays involved, and yes, there
is audible difference at any audible frequency when you change them.
jj, curmudgeon and tiring philalethist
Sascha Erni, lc <l...@escorp.unizh.ch> wrote:
>As you do with headphones -- differences in pressure. The human ear
>has quite a few very interesting mechanisms to orientate itself in an
>acoustic field; phase is only one of them.
What's more, phase sensitivity is pretty astonishing, look into the
effects one can hear in either headphones or loudspeaker testing.
>But it is a psychoacoustic fact that humans are not able to pin down
>locations solely with frequencies <60Hz. Not accurately, that is (and
>at something like 45Hz not at all).
There is little information on imaging at that frequency. None the
less, one can get a sense of space, etc from this frequency...
Mark J. Young
>
> On 16 Sep 1998, Nousaine wrote:
>
> > Cmon you are begging the question. With a 20 foot wavelength how do
> > you hear 'stereo' when your ears are less than a foot apart?
>
> has quite a few very interesting mechanisms to orientate itself in an
> acoustic field; phase is only one of them.
>
> locations solely with frequencies <60Hz. Not accurately, that is (and
> at something like 45Hz not at all).
The head acts as a low pass filter. For frequencies less
than 300 Hz there is barely any binaural intensity difference
(e.g., at 15deg off center, there are about 25%, 150% and 300%
differences for 300 Hz, 1000 Hz and 10000 Hz tones, respectively).
Of course this doesn't mean that a low frequency stereo
presentation won't sound different since you can create
non-ecological patterns of stimulation (i.e., speakers
or headphones circumvent the head's shadow).
Mark
Nousaine
locations solely with frequencies <60Hz. Not accurately, that is (and
<<There is little information on imaging at that frequency. None the
less, one can get a sense of space, etc from this frequency...>>>
Okay which is it here. Can you hear "stereo" at 50 Hz or not? What is
stereo good for anyway...spatiality, imaging? I agree there is no
'imaging' information at these frequencies.
That's the point. With recorded commercially recorded program material
imaging and location are a function of higher frequency components for
two reasons 1) there is little material with out-of-phase information
at low frequencies and 2) at low frequencies you are in the resonant
zone is a playback room where standing waves dominate.
Now there is an argument that spaced reproducers are needed to avoid
that in-the-head bass sense that you sometimes get. I am still
skeptical but willing to consider experiental verification. So far it
seems that multiple transducers at low frequencies other than in
corners causes more problems (standing wave nulls) than it fixes. Even
it we pursue the spaciouness thread I still fail to see why the signal
would need to be "stereo" at low frequencies.
Nousaine
ramp and a 100 hz low pass filter?<
<<An off-axis tuba, playing the tuba part of transcripted show tunes.
There are acutally several different delays involved, and yes, there
is audible difference at any audible frequency when you change them.>>
Okay this sounds good (no pun intended) but how do you disconnect the
upper frequency range and the start transient from the localization of
the tuba? Are saying that you can still tell the location of the tuba
with a slow ramp and a 100 Hz low pass? And the location changes when
you combine the channels below 80 Hz or something? Tonality changes?
Sascha Erni, lc
> In article <6trh1p$n...@news01.aud.alcatel.com>,
> Sascha Erni, lc <l...@escorp.unizh.ch> wrote:
> >As you do with headphones -- differences in pressure. The human ear
> >has quite a few very interesting mechanisms to orientate itself in an
> >acoustic field; phase is only one of them.
>
> What's more, phase sensitivity is pretty astonishing, look into the
> effects one can hear in either headphones or loudspeaker testing.
There are at least two completely different kinds of stereo imaging:
phase-based and intensity-based. According to situation and frequency
(-ies) involved, the human ear takes the most appropriate route. In
headphones situations :), we normaly pin down the position of a
phantom-noise with differences in intensity, not phase; thus the "in the
head" effect takes place.
> >But it is a psychoacoustic fact that humans are not able to pin down
> >locations solely with frequencies <60Hz. Not accurately, that is (and
> >at something like 45Hz not at all).
>
> There is little information on imaging at that frequency. None the
> less, one can get a sense of space, etc from this frequency...
True.
BTW, some GREAT low-frequency stereo imaging can be found on the ECM
record by Niels Petter Molvaer called "Khmer." Astounding record (if you
can find it).
Greetings,
lc
Sascha Erni, lc
> >But it is a psychoacoustic fact that humans are not able to pin down
> locations solely with frequencies <60Hz. Not accurately, that is (and
> Aat something like 45Hz not at all)....<
> <<There is little information on imaging at that frequency. None the
> less, one can get a sense of space, etc from this frequency...>>>
> Okay which is it here. Can you hear "stereo" at 50 Hz or not? What is
> stereo good for anyway...spatiality, imaging? I agree there is no
> 'imaging' information at these frequencies.
Normally, you can't hear "stereo" at 50Hz or so. But the threshold is
floating; I can hear stereo at a little over 60Hz, whereas most of my
friends can't locate frequencies under 80Hz. Must have something to
do with being a bass player... ;-)
Greetings,
lc
jj, curmudgeon and tiring philalethist
Sascha Erni, lc <l...@escorp.unizh.ch> wrote:
>There are at least two completely different kinds of stereo imaging:
I'd say 3.
>phase-based and intensity-based.
And first-arrival based, for non-stationary signals at higher
frequencies.
>According to situation and frequency
>(-ies) involved, the human ear takes the most appropriate route. In
>headphones situations :), we normaly pin down the position of a
>phantom-noise with differences in intensity, not phase; thus the "in the
>head" effect takes place.
Um, most (including me) think that's due to HRTF effects, mainly, not
intensity, per-se, as well as the fact that with headphones there's
no inter-aural mixing.
>BTW, some GREAT low-frequency stereo imaging can be found on the ECM
>record by Niels Petter Molvaer called "Khmer." Astounding record (if you
>can find it).
Hmm. Have to try. What sort of music is it?
jj, curmudgeon and tiring philalethist
Nousaine <nous...@aol.com> wrote:
>>But it is a psychoacoustic fact that humans are not able to pin down
>locations solely with frequencies <60Hz. Not accurately, that is (and
>Aat something like 45Hz not at all)....<
><<There is little information on imaging at that frequency. None the
>less, one can get a sense of space, etc from this frequency...>>>
>Okay which is it here.
Please do not introduce a dichotomy where none exists. There is no
imaging, per-se, although a WEE bit can be created in headphones,
that's not something you'll get from any normal sort of recording.
This does NOT mean that you can't affect the sense of space around
the listener, or the sense of "surround".
jj, curmudgeon and tiring philalethist
Nousaine <nous...@aol.com> wrote:
>Okay this sounds good (no pun intended) but how do you disconnect the
>upper frequency range and the start transient from the localization of
>the tuba?
A filter? You know, FIR? I must be specific, the filter was at 100Hz,
we weren't INTENDING to run this test.
>And the location changes when
>you combine the channels below 80 Hz or something?
The location and the sense of envelopment change when you change
the inter-channel time delay.
Nousaine
<<Please do not introduce a dichotomy where none exists. There is no
imaging, per-se, although a WEE bit can be created in headphones,
that's not something you'll get from any normal sort of recording.
This does NOT mean that you can't affect the sense of space around the
listener, or the sense of "surround". >>>
I think we are on the same wavelength here. Okay let's get
practical. What are the benefits of using two subwoofers (separate
cabinet crossed over at some frequency) instead of one? Does use of
two automatically mean you get more spaciousness? Will four be better?
How would they be placed?
Austin Jackson
> The higher frequency
>content gives all the location and spaciousness cues on modern
>recordings.
This may be true, but when my sub is far to the side of a speaker,
there is still a sensation that there is more "pressure" comming from
that side of the room, even though the stereo image is pretty much
intact. The pressue is something that is felt with the body, not
heard with the ears -- so it's not really "imaging" that's the
problem.
Nousaine
<<A filter? You know, FIR? I must be specific, the filter was at 100Hz, we
weren't INTENDING to run this test.>>>
>And the location changes when
>you combine the channels below 80 Hz or something?
<<<The location and the sense of envelopment change when you change
the inter-channel time delay.>>>
And because you made the original recording you (what and how was the
microphone placement) have a reference of correct playback. What were
the differences? How did things change. What was the playback speaker
arrangement?
Thomas Nulla
>The location and the sense of envelopment change when you change
>the inter-channel time delay.
How should we arrange stereo subs in order to maximize the sense of
being in a very large space? This sounds potentially beneficial from
an audiophile point of view.
Thanks,
Thomas <now playing: Frank Zappa, "The Best Band You Never Heard">
http://www.io.com/~nulla (high fidelity and miscellany)
Machining page, John Dunlavy r.a.* archive to 17 July 1998
[excessive sig deleted -- deb]
D Kirkland
better resonance control than one sub.
Anybody able to give some input on this?
All I seem to here lately is that it is best to just use one sub
in a corner which will activate more room modes. But resonances
ALWAYS degrade the accuracy somewhat, depending on how much
resonance there is.
Personally I am interested in ways to get a flat frequency
response while REDUCING resonance (gain accuracy). And I would
gladly give away some efficiency for such.
If anybody has done some studies along these lines, I would love
to here about it! Enough with activating modes nonsense! ;)
Anybody?
dan
PSiu89449
writes:
>I think we are on the same wavelength here. Okay let's get
>practical. What are the benefits of using two subwoofers (separate
>cabinet crossed over at some frequency) instead of one? Does use of
>two automatically mean you get more spaciousness? Will four be better?
>How would they be placed?
I do not even wish to pretend to know much about the sicentific side
of this, but the following might perhaps stimulate some deeper
thoughts and understanding of mono subwoofer vs. multiple.
With point source, all wave front emit from a point in space. If this
single drive source is capable of reproduction in perfect phase,
considering that time is ideal, we should theoretically but arguably
obtain perfect reproduction.
In a simulated point source speakers, where Thiel & some Dunlavy comes
to mind, we have multiple drivers where their combined wave output
simulate a point source. Wave front of each drivers pretty much arrive
our ears at the same time but at slightly different vertical
angle. Henceforth, these wave launch's horizontal arrival displacement
approaches zero. They are generally characterized as great imaging and
spacious tranducers, but not as ideal as the aboved mentioned
hypothetical speaker.
Here is the hypothesis I'm trying to derive. With speakers and
subwoofers systems, wouldn't this horizontal angular offset play a
part in imaging quality? I know that we can't reliably preceive
directional clues with low frequencies, and the lower it goes, the
harder it is to distinguish. But, thus far, we had been discussing
this topic on the basis of wave length, distance between our ears,
etc. Based on personal observations, laymen at best, stereo subwoofers
placed at roughly the same horizontal angle as the main speaker does
sound more convincing.
Also tried additional pair of stereo subwoofer plus one mono sub at
extreme nearfield position with different results.
In article <6trkkj$q...@news01.aud.alcatel.com> "Sascha Erni, lc"
<l...@escorp.unizh.ch> writes:
>Normally, you can't hear "stereo" at 50Hz or so. But the threshold is
>floating; I can hear stereo at a little over 60Hz, whereas most of my
>friends can't locate frequencies under 80Hz.
I can truly relate to this experience. I have two sets of low
distortion stereo subwoofers in my room one placed at roughly the same
horzontal angle with my satellite panels. The other pair I tried
placing at exact center between my satellites. The test was done
driving either subwoofer pairs in stereo or mono while overall phase,
arrival time, and room factors were carefully compensated by digital
means. The difference in imaging and spaciousness between them are
pretty audible to me and some friends while others can't preceive any.
Sorry, I can't provide any real scientific fact or proof, but perhaps
someone here can better explain what I preceive.
Best Regards
Paul Siu
PDietzel
(Nousaine) in part:
I agree. This phenomenon drives me nuts, as much as out of phase
speaker drivers. I can live with one subwoofer when it's centered and
crossed over low enough.
Nousaine
>This may be true, but when my sub is far to the side of a speaker,
there is still a sensation that there is more "pressure" comming from
>that side of the room, even though the stereo image is pretty much
intact. The pressue is something that is felt with the body, not heard
with the ears -- so it's not really "imaging" that's the problem. >>
Yes this is an issue but more often I find that the effect is related
to vibration and/or rattles. etc. There is also a strong psychological
effect because you already 'know' where the subwoofer is.
Nousaine
<<<All I seem to here lately is that it is best to just use one sub in a corner
which will activate more room modes. But resonances ALWAYS degrade the
accuracy somewhat, depending on how much resonance there is.>>>
What resonances are you speaking of? What do you suppose room modes
are if not resonant conditions?
Sascha Erni, lc
> In article <6tt7no$mmh$1...@agate.berkeley.edu>,
> Sascha Erni, lc <l...@escorp.unizh.ch> wrote:
> >There are at least two completely different kinds of stereo imaging:
> I'd say 3.
> >phase-based and intensity-based.
> And first-arrival based, for non-stationary signals at higher
> frequencies.
OK, but has this any effect on the reproduction of phantom-sources?
> >According to situation and frequency
> >(-ies) involved, the human ear takes the most appropriate route. In
> >headphones situations :), we normaly pin down the position of a
> >phantom-noise with differences in intensity, not phase; thus the "in the
> >head" effect takes place.
> Um, most (including me) think that's due to HRTF effects, mainly, not
> intensity, per-se, as well as the fact that with headphones there's
> no inter-aural mixing.
> >BTW, some GREAT low-frequency stereo imaging can be found on the ECM
> >record by Niels Petter Molvaer called "Khmer." Astounding record (if you
> >can find it).
> Hmm. Have to try. What sort of music is it?
Wow, THAT's a hard one... think of Miles Davis playing Scandinavian
Jazz with a E-Bow-guitar player, a hard-core drummer, and a DJ.
No, actually the music IS nice. Probably one of the "most important"
records of the 90s.
Greetings,
lc
uh OH!
>>wes...@mindspring.com (Austin Jackson) wrote, and quoted nous...@aol.com
>(Nousaine) in part:
>
>>> The higher frequency
>>>content gives all the location and spaciousness cues on modern
>>>recordings.
>>
>>This may be true, but when my sub is far to the side of a speaker,
>>there is still a sensation that there is more "pressure" comming from
>>that side of the room, even though the stereo image is pretty much
>>intact. The pressue is something that is felt with the body, not
>>heard with the ears -- so it's not really "imaging" that's the
>>problem.
>
>I agree. This phenomenon drives me nuts, as much as out of phase
>speaker drivers. I can live with one subwoofer when it's centered and
>crossed over low enough.
As much as I prefer two subs for the physical presence, there has been
a couple of occasions where a single subwoofer placed in a corner
didn't call much attention to itself and hence, irritate the hell out
of me. One was a Velodyne crossed over at 40 Hz supplementing a pair
of full-range speakers. The other was an M&K satellite system, whose
subs use two 18 dB/octave crossovers, one adjustable, one fixed at 125
Hz, in tandem, to yield a 36 dB/octave final roll-off. The former was
the least compromising, though the second most practical, and not
ridiculously behind in terms of convincingness. Actually, with the
right components behind them, the M&K's were pretty damn good, despite
the satellites' general tendency to rip up on amplifiers. One doesn't
usually think of a satellite style speaker as a power hog, but they'll
drive most receivers, and some outboard amps, into a raspy, dry heave
at anything above modest levels.
jj, curmudgeon and tiring philalethist
Nousaine <nous...@aol.com> wrote:
>I think we are on the same wavelength here. Okay let's get
>practical. What are the benefits of using two subwoofers (separate
>cabinet crossed over at some frequency) instead of one? Does use of
>two automatically mean you get more spaciousness? Will four be better?
>How would they be placed?
You should have two. They should be within about .5 milliseconds of
the midrange they go along with.
You could have more.
They should be one to either side of the listener.
jj, curmudgeon and tiring philalethist
Thomas Nulla <nu...@io.com> wrote:
>How should we arrange stereo subs in order to maximize the sense of
>being in a very large space? This sounds potentially beneficial from
>an audiophile point of view.
Within a half-millisecond or so of the midrange the channel goes
along with.
Howard Ferstler
> Curtis Leeds notes:
> <<<Well, I haven't made the bet - but it would be a safe one. Many people who
> espouse this "all bass is mono" theory have never experimented to test the
> belief.>>>
> Well I have. I searched to find programs with out-of-phase
> information at subwoofer frequencies (no small feat...how are you
> going to get 'stereo' at very low frequencies with the wavelengths
> involved...and even if you get it recorded how can you hear it when
> your ears are only 8-inches apart.) Then I placed a pair of identical
> subwoofers under a pair of left and right satellite speakers. Blind
> listeners were unable to tell when the source was switched between
> stereo and mono with an 80 or 100 Hz crossover frequency.
> <<<It's simply mistaken to believe that all bass is essentially mono. I've
> experimented with various woofer locations and configurations (I don't use subs
> - instead, I use a full-range speaker system with separate woofer towers), and
> there's no question that in my room and with my equipment, there's a big
> difference between mono and stereo bass.>>
> It is true that differing locations bring different 'bass'
> presentation due to standing waves. But again there are precious few
> sounds that have only low frequency sound. The higher frequency
> content gives all the location and spaciousness cues on modern
> recordings.
Yes, double subs, or double full-range speakers, can get you into all
sorts of bass problems that a mono sub automatically solves.
I have a somewhat unique situation, myself. My surround processor
will allow a bit of mid-bass spillover from the center channel to the
left and right mains if it is set in the Dolby "normal"
(small-center) mode. This happens, even if I use the subwoofer
output and run all the bass from all the satellites to the sub.
To solve the problem, I run the center at full bandwidth, and include
a sub there, too. One sub (the one handling most of the bass) is in
the left-front corner of the room, and the other (the center-channel
sub) is in the right-front corner. The front wall is 22 feet long,
so they are quite far apart.
This does not cause the problems that a typical stereo-sub hookup
would create. With standard stereo program material, the center sub
is inoperative. With Dolby Pro Logic material, it tends to dominate,
because low bass is almost completely mono, and the center gets the
mono bass. With Dolby Digital material, the other sub (which handles
the LFE, as well as the bass to the other four channels), does most
of the work. So, rarely do both subs compete with each other and
cause cancellation artifacts..
If I had a processor that did not display the mid-bass spillover
problem, I would definitely opt for a mono sub, with the center set
for "small," and like Tom Nousaine suggests, I would put it into the
corner.
Howard Ferstler
Chris Caudle
(regarding sub-woofers)
> You should have two. They should be within about .5 milliseconds of
> the midrange they go along with.
I'm going from memory here, but isn't a good rule of thumb that sound
travels approximately 1 foot in 1 millisecond? So, the sub should be
within 6 inches of the main speaker?
Given that, what are the practical implications of this? Does this mean
that separate cabinets for satellite and sub are out? You won't be able to
do the trick of positioning the sub for best low frequency response, and
placing the upper range speakers for best imaging (usually based on
listening room reflections) if you have to place them withing 6 inches of
each other. For that matter, several full range systems have trouble
getting the woofer within 6 inches of the mid-range drivers (the NHT
systems with the woofer on the side of the cabinet come to mind).
What happens if the sub-woofers are farther than 0.5ms from the main
drivers, e.g. subs in the corners of the room, and the main speakers a
couple of feet in?
--
Chris Caudle
uh OH!
>jj, curmudgeon and tiring philalethist <j...@research.att.com> wrote
>(regarding sub-woofers)
>> You should have two. They should be within about .5 milliseconds of
>> the midrange they go along with.
>> Copyright j...@research.att.com 1998, all rights reserved
>
>I'm going from memory here, but isn't a good rule of thumb that sound
>travels approximately 1 foot in 1 millisecond? So, the sub should be
>within 6 inches of the main speaker?
Not necessarily. They should be the same distance away from the
listening position as the main speakers, plus or minus 6 inches.
Notice that he said milliseconds, not distance. You could also use
the DSP in dolby digital processors to adjust the delay to the
speakers, which seems to be a useful feature here, eh? I don't know
if they've all got a distance/delay setting for the subwoofer, but
it's an option on at least a few. Only problem is, most of them run
the subwoofer mono. Ooops.
>Given that, what are the practical implications of this? Does this mean
>that separate cabinets for satellite and sub are out? You won't be able to
>do the trick of positioning the sub for best low frequency response, and
>placing the upper range speakers for best imaging (usually based on
>listening room reflections) if you have to place them withing 6 inches of
>each other. For that matter, several full range systems have trouble
>getting the woofer within 6 inches of the mid-range drivers (the NHT
>systems with the woofer on the side of the cabinet come to mind).
Time alignment versus physical proximity.
>What happens if the sub-woofers are farther than 0.5ms from the main
>drivers, e.g. subs in the corners of the room, and the main speakers a
>couple of feet in?
The bass is a few milliseconds late, unless you've applied an
appropriate delay to the main channels.
Andre Yew
>I'm going from memory here, but isn't a good rule of thumb that sound
>travels approximately 1 foot in 1 millisecond? So, the sub should be
>within 6 inches of the main speaker?
Well, you could use a digital delay to "move" the sub up to within .5
milliseconds of the midrange.
>each other. For that matter, several full range systems have trouble
>getting the woofer within 6 inches of the mid-range drivers (the NHT
>systems with the woofer on the side of the cabinet come to mind).
I remember Ken Kantor saying that the woofers of the 3.3 have
compensation in their xover to take care of this, but I believe he
doesn't believe in time-alignment tighter than 2 or 3 ms, so that may
not solve it either.
The time-aligned speaker genre shouldn't have difficulty with this.
I think Thiels, Dunlavys, and Vandersteens all have fairly tight time
alignment, with the Dunlavys being especially fastidious about it.
--Andre
--
PGP public key available
PSiu89449
Ideally, we have an ideal subwoofer in an ideal room at some ideal
location, such as room corner, to handle only the low frequencies
where we can't detect its location. But unfortunately, we are all
living in a real world.
In this real world, we try to place a real mono subwoofer in a room
corner to obtain the best bass reinforcement. If the crossover is set
low enough, we hope to preceive no direction clue what so ever from
this one location. At this or any other locations, this subwoofer
will create a high preasure zone where it modulates any nearby
surface, floor and walls inclusive. Within this high preasure zone,
wouldn't the immediate surface vibrate and modulate enough to give
off higher frequence content thus producing location clues?
Best Regards
Paul Siu
ROBERT C. LANG
> I'm going from memory here, but isn't a good rule of thumb that sound
> travels approximately 1 foot in 1 millisecond? So, the sub should be
> within 6 inches of the main speaker?
> Given that, what are the practical implications of this? Does this mean
> that separate cabinets for satellite and sub are out? You won't be able to
> do the trick of positioning the sub for best low frequency response, and
> placing the upper range speakers for best imaging (usually based on
> listening room reflections) if you have to place them withing 6 inches of
> each other. ..........................
This may sound overly simplistic, but why not call the manufacturer
of the subs being considered? Talk to the designer(s). They would
love to talk to you. At best you can determine if the subs can be
placed near the "ideal" location as intended by the designer. Or you
can get alternate recommendations on how the subs will fit in your
room with your satellites. At worse you can determine that the subs
will not work at all in your room before you purchase them.
I spoke at length with the designer of my two sub system and even
paid paid him a visit, even though he lived over 1200 miles away just
to get the best ideas on placement. For my system he explained that
the each sub should be placed 6" from the back wall (facing the
wall), 2 ft from the side wall, 18 inches behind the (and outside) of
the satellites. This places the satellites approximately 4 ft. from
the back wall and about 5 ft from each side wall. Now this represents
the "ideal" placement. Other placement positions would also work and
the designer had alternate placement recommendations.
I had two big advantages: 1) My listening room is large enough to
accomodate the "ideal" placement. 2) The designer of my system was
the sole designer of the entire 2 sub, 2 satellite system. So all
speaker pieces and the crossover were designed with each other in
mind. This is a HUGH advantage when it comes to placement and
integration of satellite and subs.
One other example, years ago I purchased a pair of Ohm F
loudspeakers. They were a lot more controversial than they should
have been because users/reviewers simply did not know how to set them
up or provide proper ampliication. I didn't either. I called the
manufacturer (before the purchase), talked to some technicians (more
than one) and learned a tremendous amount about the loudspeaker and a
little (tiny) bit about speaker design in general.
I remember TAS did a review of the OHM F and had them placed against
the back wall driven by a tube amplifier, in a small room. A call to
the manfacturer would have taught them that the speakes should best
be 4 ft from any wall and driven driven by a high voltage, high
damped solid state amp.
Frankly talking to the designer can be one of the fun parts of
putting together a high end system and one of the most educational
parts of the process.
Robert C. Lang
uh OH!
>dbk6a50 wonders:
It's nice to entertain the idea of bass without resonance, until you
realize that it requires not only drivers that have their crossovers
and LF limits outside of the playback range, but also rooms with no
walls. If you're going to get real SPL in low frequencies under
those conditions, you're going to need a lots of displacement and
lots of power. No, full-range ESL's aren't going to cut it, unless
you've got twenty or thirty pairs stacked to form a continuous
baffle.
jj, curmudgeon and tiring philalethist
Chris Caudle <cca...@pdq.net> wrote:
>I'm going from memory here, but isn't a good rule of thumb that sound
>travels approximately 1 foot in 1 millisecond? So, the sub should be
>within 6 inches of the main speaker?
They should be such that their distance to the listener is withing
about 6" of the speaker, yes. They can move sideways a bit,
as long as the movement doesn't introduce an interaural distance
of under about 60 microseconds.
Figure that you have 2 ears, .8 ms apart, for that purpose.
>Given that, what are the practical implications of this?
Well, you surely have a point.
>Does this mean
>that separate cabinets for satellite and sub are out?
IF you're going to get the last little bit, perhaps.
Nousaine
In this real world, we try to place a real mono subwoofer in a room
corner to obtain the best bass reinforcement. If the crossover is set
low enough, we hope to preceive no direction clue what so ever from
this one location. At this or any other locations, this subwoofer will
create a high preasure zone where it odulates any nearby surface,
floor and walls inclusive. Within this high preasure zone, wouldn't
the immediate surface vibrate and modulate enough to give>>>
Well the direct field of a subwoofer can vibrate any surface it's
close to. Rememebr the energy being transmited into the room is the
same. the power ampliifier and speaker displacment hasn't chnaged with
placment. The key to corner placmen tis that it provides a more even
distribution of that energy in the room. off higher frequence content
thus producing location clues?
PSiu89449
writes:
>Well the direct field of a subwoofer can vibrate any surface it's
>close to.
Precisely.
>Rememebr the energy being transmited into the room is the
>same. the power ampliifier and speaker displacment hasn't chnaged with
>placment. The key to corner placmen tis that it provides a more even
>distribution of that energy in the room.
Correct.
> off higher frequence content thus producing location clues?
The point I'm trying to illustrate is that the surfaces closest to
the subwoofer will vibrate the most due to this high preasure zone.
These surfaces are more likely to modulate and possibly give off
higher frequency content thus giving away the location clues of a
nearby subwoofer. Henceforth, one mono subwoofer in one room corner
MAY compromise stereo reproduction.
I used to use two pairs of stereo subwoofers plus one mono sub in my
main system. One stereo pair against the front wall immediately
behind my satellites, another pair flanking my seat, and one monster
mono immediately behind the same. This roughly randomize the preasure
zone across the entire room and gave me very even bass response. The
only problem then was the preceived soundstage and image specificity
wasn't maximized. It wasn't until I retire my rear mono sub and move
both stereo subwoofers to the front did I realize the amount of
stereo information I was compromising. No, I'm not here saying that I
can directly preceive location clues of a low distortion subwoofer.
But read further.
Currently, a pair of huge sub-towers are against the front wall
measuring almost 2 feet from the side wall and a pair of large subs
flanking the outside my mid/high satellite panels. The horizontal
angular displacement vs satellites in reference to my seating
position is +/- 7 degrees. The arrival time of the flanking subs are
within 1ms of the satellites as confirmed by LAUD measurements. The
sub-towers are low-passed at 40Hz.
With this setup, I'd taken into consideration the overall horizontal
angular displacement, surface modulated inclusive. Phase were
carefully corrected via both sub system's variable phase control.
Overall room response is fairly flat and is further corrected by
digital means. Arrival time of the sub-towers are also partically
aligned by the same. And the end result is a vast improvement in
stage precision and image specificity. The overall stage opens up
much more than my previous setup.
There are certainly more than one way to arrange any subwoofer
system. But room loading and frequency response are only two of many
important factors we should consider. Horizontal angular displacement
and surface modulated frequency content are only two more I'm trying
to introduce here in this forum. Henceforth, the argument of
subwoofer being mono or stereo is just an exercise of debate. One
must sometimes stand back and look at the overall picture to uncover
other posibilities.
Best Regard
Paul Siu
TEAShea
>main system. One stereo pair against the front wall immediately
>behind my satellites, another pair flanking my seat, and one monster
>mono immediately behind the same.
Now, we know where the earthquakes were coming from. Seriously, I would be
interested to know how you powered array and your current array of
subwoofers. How smooth and integrated is the sound you are able to achieve?
Do you use active crossovers?
Tom Shea
- TEA (Tom)
Nousaine
<<<With this setup, I'd taken into consideration the overall horizontal
angular displacement, surface modulated inclusive. Phase were carefully
corrected via both sub system's variable phase control.
Overall room response is fairly flat and is further corrected by digital means.
Arrival time of the sub-towers are also partically
aligned by the same. And the end result is a vast improvement in stage
precision and image specificity. The overall stage opens up
much more than my previous setup.
There are certainly more than one way to arrange any subwoofer system. But room
loading and frequency response are only two of many important factors we should
consider. Horizontal angular displacement and surface modulated frequency
content are only two more I'm trying to introduce here in this forum.
Henceforth, the argument of subwoofer being mono or stereo is just an exercise
of debate. One must sometimes stand back and look at the overall picture to
uncover other posibilities.>>>
Welll Icertainly agree that stopping rattles and buzzes is a good
idea. I do the same thjng by buttoning up any 'modulating surfaces."
On the otehr hand I have experimented at length with distributed
multiple subwoofers and found that they always introduce response
errors and make energy distribution in the room more uneven.
Have an AES paper (103rd Convention, Preprint 4558 (H-9)). Would be
happy to share with you. The amin problem with multiple sources
(inless in closed corners) is that they 'unexcite' and reexcite some
room modes. this tends to make peaks higher and insert nulls that
may not be present with corner placement.
Without flat frequency response you always have time domain errors.
However it is possible to have plenty of time error with no audible
consequence IF frequency response remains flat. All pass filters
anyone?
PSiu89449
>Now, we know where the earthquakes were coming from. Seriously, I would be
>interested to know how you powered array and your current array of
>subwoofers. How smooth and integrated is the sound you are able to achieve?
>Do you use active crossovers?
Earthquakes.........Thats funny.........
In my continual search for better sound, many pieces of equipments
had came through my doors. Subwoofers I'd sold in this past year were
a pair of ACI Sub-1 and a Velodyne ULD 18-II. Subwoofers I currently
have scattered around my house are 2 pairs of self build Madisound
15" Sledge Hammer, one Legacy Foundation Dual 12", a pair of
Definitive Tech PF-1800, a pair of Genesis 900, and a pair of Genesis
II servo-sub tower (part of G2 system). Sledge Hammers are collecting
dust. Legacy & Definitive Tech in home theater system. All Genesis in
dedicated music room.
Genesis subwoofers are self powered servo with adjustable highpass,
lowpass, phase, & volume. Definitive are also self powered, no servo
but adjustable lowpass, phase, & volume. Legacy is currently driven
by a pair of old Denon 6600 mono blocks. Electronic crossovers are
Madisound Sledge Hammer 3 way, Bryston 10B-XLR, and 10B-Sub XLR.
Other amps dedicated for passive subs are a pair of Bryston 4B-ST and
an old Soundscraftmen H5002. In case one wonders, I have a total of
eight dedicated power lines for both systems. No major quakes but
just minor after shocks....... Laugh!
For those who know me, I had been an advocate of multiple subs.
However, number doesn't a good system make. It is the proper setup
and technique that one need to achieve good sound. My reasoning
behind multiple subs are low overall distortion, multiple room
loading to achieve smooth response, super low extension, and great
dynamics. Futhermore, I also rely heavily on cutting edge digital
technologies such as multiple units of SigTech and Z-System Rpt-1 to
further refine system integration.
The first objective is to obtain, as much as possible, unassisted
flat frequency response. Where possible, satellites and subwoofers
are positioned to achieve <1ms arrival time. Weeks were spend
juggling with minute speaker adjustments, positions, and crossovers.
With my home theater system, all five channels are full range. Center
channel is a pair of Genesis 700, above and below the screen,
highpassed at 80Hz. The lows are handled by the Legacy.
Unfortunately, due to domestic reasons, this sub's is positioned
immediately next to the main couch where arrival time is 4ms ahead of
the 700's. Front main channels are handled by a pair of APM-1 with
its build-in powered servo subs. Rear Channel is a pair of Mirage
M3Sis to be replaced by the APM-2's when they arrive. Subwoofer
channel is necessary mono, either AC-3 or Dolby Prologic, handled by
the Definitive Tech pair. Overall response of all channels are
adjusted to within +/- 4dB full range before SigTech. After SigTech,
all channels are matched within +/- 0.5dB full range. Horizontal
angular displacement is a non-issue with the exception of the center
channel.
With my dedicated music room, the main GII sub-towers are placed
against the front wall and almost 2' in from the sides. They are
internally highpassed at 16Hz and externally lowpassed at 40Hz via
Bryston 10B-Sub XLR. The 900 pair and mid/high panels are 8' from
front wall and placed within 1ms of each other. The 900 are
highpassed at 32Hz and lowpassed at 110Hz. Horizontal angular
displacement in reference to panels are +/- 7 degrees for both subs.
Subwoofer phase are adjusted to the direct inverse of the deepest
null angle. Arrival time of the sub-towers are necessary longer but
not too much of an issue due to the low lowpass. Due to room
problems, the best I can achieve was +/- 6dB from 20 to 1kHz
unassisted. Furthermore, I don't particularly like Arnie's choice in
the powerband hump which contributes much to the +/- 6dB. It is a
wonder why magazine reviews didn't point to this abnormality. After
SigTech, it is almost ruler flat as usual. Match between both
channels are within 0.25dB. Most listening are done without further
modifications but with occasion tailoring via Z-System, material
pending. Since Genesis subs are self powered, no external amps are
necessary. Four sets of tube & SS monster amps, one being two pairs
of Class A monos, are used in turn for this system. Due to the
complex loads via multiple amps, internal and external, and the
desire to connect them directly to the DAC for the purest signal
drive, two units of Classe DAC-1's are deployed. With the help of
liberal amounts of passive room treatment devices, RTA of this room
is in the low 0.2ms as confirmed via LAUD.
With this system, the ends justifies the means. The means are
involving, but the ends are rewarding.
Best Regards
Paul Siu
PSiu89449
writes:
>Welll Icertainly agree that stopping rattles and buzzes is a good
>idea. I do the same thjng by buttoning up any 'modulating surfaces."
>On the otehr hand I have experimented at length with distributed
>multiple subwoofers and found that they always introduce response
>errors and make energy distribution in the room more uneven.
Rattles and buzzes is certainly a major concern. Short of concrete
reinforcement, average domestic listening room exhibits some form of
surface modulations. However minute in amplitude, the combined area
of immediate vibrating surfaces will add up to some amounts of
acoustic output. The total output, depends on surface material and
construction type, is very difficult to predict.
One may argue that delayed reflected signal is much higher in energy
content and this is entirely correct. This first reflection accounts
for most of the total surface related output. However, take into
consideration that most low frequencies will simply leak through and
most higher frequencies will reflect. Energies from each perspective
satellites will naturally cause this reflection. Being stereo in most
applications, horizontal angle displacement of these close reflected
energies are naturally minimum. But when we introduce a substantial
surface modulated energy source at a large horizontal displacement
angle, such as right channel bass information in a mono subwoofer
located at left corner, preceived soundstage will distort.
You are absolutely correct regarding uneven energy distribution with
multiple subwoofers. However, with careful tuning and placement, one
can often compensate for this problem. Audiophile being mostly a
solitude breed, we only have to achieve good overall response at
listening position. And most often than not, this is easier to
achieve with multiple subwoofers and judicious electronic crossover
adjustments. This at least is based on my personal experience.
However, the point I'm trying to introduce here is not about bass
amplitude response but the effect of subwoofers have on preceived
soundspace and image.
>Have an AES paper (103rd Convention, Preprint 4558 (H-9)). Would be
>happy to share with you. The amin problem with multiple sources
>(inless in closed corners) is that they 'unexcite' and reexcite some
>room modes. this tends to make peaks higher and insert nulls that
>may not be present with corner placement.
Thanks. I would love to learn more from this paper and will e-mail
you privately with my fax number. Again, with careful choice of
placement and crossover points, I was able to obtain good results
most of the time. With single sub against a corner, I often have to
resort to EQ to obtain the same.
>Without flat frequency response you always have time domain errors.
>However it is possible to have plenty of time error with no audible
>consequence IF frequency response remains flat. All pass filters
>anyone?
At least we can always correlate good time and amplitude response
with good step response as dictated by FFT.
Best Regards
Paul Siu
A 911S
their own controls, becuase you will find yourself having to take in
way to much bass on one medium (lets say music), and not enough bass
in another (Home theater for example), being able to toy with the
sound is a great pleasure.
D Kirkland
: What resonances are you speaking of? What do you suppose room modes
: are if not resonant conditions?
Exactly! And you are always saying that it is best to just use
a single sub in a corner location to excite as many room modes
as possible.
But I am much more interested in REDUCING resonances!
And I once read at NHT's web site where they said that two subs
offer better control over room resonances than one sub. I am
wondering if anybody can give more input to this.
dan
TVodhanel
However, number doesn't a good system make. It is the proper setup
and technique that one need to achieve good sound.<<<
When you say you are an advocate of multiple subwoofers.......are
you saying you recommend using multiple subs, on multiple channels
scattered about the room?
Or just.....multiple subwoofers, usually on the LFE, placed to
provide the flattest response over the listening position(s).?
Or......something in-between?
TV
PSiu89449
writes:
>When you say you are an advocate of multiple subwoofers.......are
>you saying you recommend using multiple subs, on multiple channels
>scattered about the room?
>
> Or just.....multiple subwoofers, usually on the LFE, placed to
>provide the flattest response over the listening position(s).?
Above all, I like to use true full range speakers on all channels; two
music only or five for H/T systems. If subwoofers are needed, I
personally prefer dedicated subs on all channels. With Dolby Prologic,
rear channel doesn't produce much deep bass informations. Furthermore,
there are no image steering. So dedicated sub aren't necessary for
the rear. But with AC-3 or DTS, surround channels contain specific
steering informations and often full range. Henceforth, I prefer full
range or individual subwoofers. Full range here means 20-20kHz.
For LFE, I use two for better room lock. But that have much to do with
my home theater's open floor plan with hudge space volume. Since I can
occassionally bottom a single PF-1800, I use two.
But regardless, it is best to have full range flat response at
viewing/listening position. Isn't that we all strive to obtain in the
first place?
Best Regard
Paul Siu
PSiu89449
Kirkland) writes:
>Exactly! And you are always saying that it is best to just use
>a single sub in a corner location to excite as many room modes
>as possible.
>
>But I am much more interested in REDUCING resonances!
>
>And I once read at NHT's web site where they said that two subs
>offer better control over room resonances than one sub. I am
>wondering if anybody can give more input to this.
I don't recall Mr. Nousaine recommending using a single sub to "excite as many
room modes as possible" in this thread. I think it was me who advocate multiple
subs to do just that. But if REDUCING resonances is your main objective, move
your system out doors and you will hear what a difference it makes.
Like all things, it is a compromise. Using a single sub at one corner will
maximize the smoothest theoritical response and activate only one set of room
resonance mode. My argument is the possibility of locating this single low
frequence source directly or indirectly thus risk damaging the preceived
soundstage and image specificity. And theoritically, if we can excite infinite
numbers of room resonance mode, we will again obtain smoothest theoritical
response.
Along the lines with NHT, I personally believe that two subs or more offers
better control and room lock, but casual setups may cause more problems than it
can solve. Two subs generates different sets of nulls and peaks across the
room. There is simply more chances that two sets of nulls may intersect thus
causing a worse case scenario. On the other hand, properly tuned, these nulls
and peaks may complement each other. Henceforth, careful setup and attention to
minor details can bring about superior results.
We are all refering to different sets of compromises and there are more than
one way to dice a chicken.
Best Regards
Paul Siu
Gordon Gilbert
Re: 1 or 2 subs?
> necessary for the rear. But with AC-3 or DTS, surround channels
> contain specific steering informations and often full range.
> Henceforth, I prefer full range or individual subwoofers. Full range
> here means 20-20kHz.
Since bass is non-directional below about 80Hz, this is
unneccessary. It could also cause response variations by creating
more room nodes with a lot of peaks and dips spread around the room.
You'll normally get the smoothest response by putting 1 subwoofer in
the corner. It doesn't matter in the slightest that AC-3 or DTS
channels are full-range. Low frequency bass can be redirected to the
subwoofer channel with no ill effects. Again, true subwoofer bass is
non-directional to the human ear. The directional clues are in the
higher harmonics, typically above 100Hz, which should come from the
individual channels in question.
--
- Gordon Gilbert | g...@sssnet.com | g...@uakron.edu -
- Visit The Audiophile Asylum for CD Reviews with Standardized -
- Sound Quality Ratings at http://pages.sssnet.com/glg -
Curtis Leeds
My thought on self powered subs: ugh! The whole point of
component hi-fi is matching equipment to other parts of the
system... including the room. With self-contained subs, the
whole woofer is down if an amp blows. yech.
Most of the best subs require the user to select his own
crossover and amplifier.
--
***************************************************
cle...@idt.net "I stood unwound beneath the skies
And clouds unbound by laws.
The cryin' rain like a trumpet sang
And asked for no applause." (Bob Dylan)
***************************************************
Curtis Leeds
> Do not confuse the "stereo" bass that occurs from about 100 Hz on up
> with the essentially mono bass that happens at lower frequencies.
I am not at all confused - I'm accustomed to genuine
full-range speaker systems.
> The stereo localization clues and stereo sense of space is created by
> sounds above 100 Hz. Bass wavelengths below that range are so long
> that it is impossible to localize them.
This is mistaken - as has been indicated in prior posts in
this thread. The inherent monophonic nature of bass is a
misnomer. Repeating it endlessly won't make the assertion
true.
PSiu89449
<g...@sssnet.com> writes:
> Since bass is non-directional below about 80Hz, this is
>unneccessary. It could also cause response variations by creating
>more room nodes with a lot of peaks and dips spread around the room.
>You'll normally get the smoothest response by putting 1 subwoofer in
>the corner. It doesn't matter in the slightest that AC-3 or DTS
>channels are full-range. Low frequency bass can be redirected to the
>subwoofer channel with no ill effects. Again, true subwoofer bass is
>non-directional to the human ear. The directional clues are in the
>higher harmonics, typically above 100Hz, which should come from the
>individual channels in question.
Short of repeating my my previous posts on this thread, yes, low bass
is NOT directional in nature. Arguments I'd made are based on
nearfield surface modulation and horizontal angular displacement.
Other interests are flat overall response at listening/viewing
position where properly implemented will avoid most if not all peaks
and dips problems. It is entirely satisfactory to use only one
subwoofer in any systems, but for the ULTIMATE in reproduction, my
personal believe and experience holds firm with multiple subs. If
AC-3 or DTS was intended to send all low bass to the LFE channel,
they would have designed and recorded only >90Hz to all five
channels. The bass management scheme on LFE channel is only a
compromise and convinence feature for those who can't accomondate
five full range channels. Again, more than one way to dice a chicken.
Best Regards
Paul Siu
Gordon Gilbert
CL> Howard Ferstler wrote:
>> The stereo localization clues and stereo sense of space is created
>> by sounds above 100 Hz. Bass wavelengths below that range are so
>> long that it is impossible to localize them.
CL> This is mistaken - as has been indicated in prior posts in
CL> this thread. The inherent monophonic nature of bass is a
CL> misnomer. Repeating it endlessly won't make the assertion
CL> true.
Ok. Prove it, then. All studies and all information I have
previously read, with the sole exception of JJ, has said that hardly
any human beings can hear directionality below about 80Hz with pure
test tones and NONE can hear any below 40Hz. With music and not pure
sine waves, you'd be extremely hard pressed to hear any directional
information at 100Hz, let alone 60Hz or 80Hz.
While it's true that bass can contain stereo information and you
can reproduce this stereo information in your room with 2 subwoofers,
it's also true that you cannot hear this stereo spatial information
below 80Hz. When you hear directionality from low bass in music,
you're hearing the harmonics, which are produced by the main speakers,
not the subwoofer. If you don't believe me, just try it yourself. I
don't know what the normally informative JJ is talking about, but I've
done this test myself and I've read about numerous such tests. Play
some test tones (and do take extreme care that sympathetic vibrations
don't give it away) of pure bass tones below 80Hz with no other
speakers playing but the subwoofer and see if you can tell which
direction it's coming from with your eyes closed. If you can't trust
yourself, have someone blindfold you and spin you around a few times
in the middle of the room before they play the tones for you. See if
you can hear any directionality at all that isn't from sympathetic
vibrations of walls and what not.
Howard Ferstler
> > Do not confuse the "stereo" bass that occurs from about 100 Hz on up
> > with the essentially mono bass that happens at lower frequencies.
> I am not at all confused - I'm accustomed to genuine
> full-range speaker systems.
> > The stereo localization clues and stereo sense of space is created by
> > sounds above 100 Hz. Bass wavelengths below that range are so long
> > that it is impossible to localize them.
> This is mistaken - as has been indicated in prior posts in
> this thread. The inherent monophonic nature of bass is a
> misnomer. Repeating it endlessly won't make the assertion
> true.
How are we going to prove this?
If a person listens to two full-range speakers and uses what they
hear coming from them to determine that "stereo" effects exist in the
low bass, then they are going about it all wrong. They should set up
two subwoofers, crossing over at below 100 Hz (or better yet, at the
more typical 80 Hz), under two satellites, and then listen to a
number of stereo recordings. Then, they should move both of the subs
to a corner off to the sides and listen again.
If they are honest with themselves, they will hear no differences,
except that the subs in the corner will produce a smoother output,
and of course a stronger one at some frequencies, due to the more
thorough coherent reinforcement. The bass wavelenghts below 80 Hz
are so long that the woofers in a normal spaced pair are already
essentially operating as a mono subwoofer to the listener's ears, in
terms of directionality, whether they are next to each other or 10
feet apart.
Interestingly, however, the spacing between two woofer systems that
far apart will result in a suckout effect (basically, the "Allison
Effect" operating at lower frequencies and between woofer systems,
rather than between a woofer and a large, reflective boundary) at a
frequency that will be determined by the spacing between the woofer
systems. This will result in a notch at a certain frequency. For
example, with a 12-foot spacing, the listener will get a notch at
about 56 Hz. If there is also a large room boundary (or boundaries)
at a distance equal to half that between the woofers (if either or
both are 6 feet from a wall, for instance), the notch will be
compounded by additional of these quarter-wavelength cancellation
effects. Note that these effects are unrelated to standing-wave
artifacts, and so cannot be eliminated by moving the listening
position. They are power-input related and not
boundary-reinforcement related.
Anyway, a mono sub, placed in a corner, eliminates this problem, and
because there is no problem with stereo bass below 80-100 Hz to begin
with, the solution does not cause havoc with the sense of stereo
bass.
Another interesting point is that stereo bass, below 80-100 Hz does
not ordinarily exist as an audible phenomonon on recordings, anyway.
Yes, some spaced-microphone recordings with really wide microphone
placement (certain Telarc recordings, and possibly recordings made
with the Decca Tree) might have a bit of stereo bass at 60-80 Hz, and
so, theoreticaly, might multi-microphone recordings of rock music,
and the like, although this is rarely the case, because the bass is
usually mixed to mono for convenience sake. However, no coincident
(Blumlein) or near-coincident (ORTF or NOS) recording will contain
stereo low bass in any way, shape, or form. So, even if full-system
woofers or double subwoofers could reproduce "stereo" low bass (which
I will reiterate, they really cannot), with most purist recordings
there is no stereo bass to reproduce. Also, all bass on LP
recordings is mixed to mono, as a matter of policy.
I have listened to mono subs with the crossover set to about 150 Hz,
and it was possible to clearly localize the subwoofer and the
phenomenon was rather disconcering. However, with the crossover set
to 100 Hz or lower, and with a decently steep LP slope, you simply
cannot detect localization clues with a mono subwoofer. Another way
to see how much stereo there is in low bass is to utilize a Dolby
Surround decoder. Set up a sub on the center channel, or use a big
center speaker with a big woofer, switch the center to
full-bandwidth, turn on the DPL decoder, and notice how much bass
comes from the center. The DPL circuitry will steer all mono signals
to the center, and the vast bulk of the bass will be coming out of
the center sub. The other bass drivers in the system will only be
reproducing upper bass. The low stuff is steered to the center,
because it is mostly mono.
I will also note that the people who build mono subs are not jerks,
and they have researched this phenomenon plenty. The only advantage
to dual subs is increased output, and the listener will get even
better results with dual units if you stack them together in the
corner.
Howard Ferstler
fer...@ibm.net
-----------== Posted via Deja News, The Discussion Network
==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your
Own
>
_________________________________________________________
DO YOU YAHOO!?
Get your free @yahoo.com address at http://mail.yahoo.com
Nousaine
<<<Like all things, it is a compromise. Using a single sub at one corner will
maximize the smoothest theoritical response and activate only one set of room
resonance mode. My argument is the possibility of locating this single low
frequence source directly or indirectly thus risk damaging the preceived
soundstage and image specificity. And theoritically, if we can excite infinite
numbers of room resonance mode, we will again obtain smoothest theoritical
response. >>>
Not exactly correct. The number and frequency of resonances (standing
waves) are fixed below about 300 Hz in a "small room". Small means
less than 10,000 cubic feet generally. A corner speaker will excite
the maximum number possible...which is why it gives smoother
frequency response. There are standing waves at EVERY frequency but
above 300 hz or so they are closely spaced and thus the sound energy
is evenly distributed in the room. At low frequencies when you fail
to excite some of the modes (which occurs with non-corner placement)
you will always roughen response.
<<<Along the lines with NHT, I personally believe that two subs or more offers
better control and room lock, but casual setups may cause more problems than it
can solve. Two subs generates different sets of nulls and peaks across the
room. There is simply more chances that two sets of nulls may intersect thus
causing a worse case scenario. On the other hand, properly tuned, these nulls
and peaks may complement each other. Henceforth, careful setup and attention to
minor details can bring about superior results.
>>>
IF they are not in a corner they cannot 'complement' each other in a
way that is smoother than corner placement. There is a school of
thought that suggests that certain a specific placement MAY produce a
greater sense of spaciousness and better 'externalization' (less
bass-in-the-head) but there is no question that corner placement
always produces the most even in-room response possible in a given
room.
Steve Zipser (Sunshine Stereo, Inc.)
> While it's true that bass can contain stereo information and you
> can reproduce this stereo information in your room with 2 subwoofers,
> it's also true that you cannot hear this stereo spatial information
> below 80Hz.
I have made recordings which sound far better using complete stereo
bass separation. There are cancellation effects in the low bass, and
there is information loss when you mono the channels in the bass. I
will not argue pro or con about the directionality, but do not say
one woofer is as good as a stereo pair, because there are definitely
recordings that will prove otherwise.
Cheers
Zip
[quoted text deleted -- deb]
--
Sunshine Stereo,Inc http://sunshinestereo.com Tel: 305-757-9358
9535 Biscayne Blvd Miami Shores, FL 33138 Fax: 305-757-1367
PASS Rega NOVA Miranda CODA Audible Illusions CEC Camelot Parasound
Audio Logic Chiro Benz-Micro Dunlavy NEAR NHT Gallo Zenith Arcane
Mordaunt-Short EAD Vans-Evers Monster/ENTECH ESP Straightwire MORE!
jj, curmudgeon and tiring philalethist
Howard Ferstler <fer...@ibm.net> wrote:
>If they are honest with themselves, they will hear no differences,
>except that the subs in the corner will produce a smoother output,
Howard, don't you think this is a wee bit of a strong claim?
>and of course a stronger one at some frequencies, due to the more
>thorough coherent reinforcement. The bass wavelenghts below 80 Hz
>are so long that the woofers in a normal spaced pair are already
>essentially operating as a mono subwoofer to the listener's ears, in
>terms of directionality, whether they are next to each other or 10
>feet apart.
I see, and if they are 10' apart, and they contain non-in-phase
information, does that mean, then, that DESPITE that not in phase
information, the positive zero-crossings of the waveform will STILL
be in the same place to within under .1 millisecond? Yes or no? If
your answer is 'no', then who's head are you using? If the answer is
'yes' then how can you deal with known timing of the human auditory
system?
Frankly, the effects are not imaging, they seem to come to me (and
some others) as a sense of "space", rather than as an 'image' in any
sense, but that is surely part of the stereo illusion, what?
jj, curmudgeon and tiring philalethist
Then you should read what I'm talking about. You get no imaging, but
you DO get a change in the spatial sense of the room, or at least I
do, and so do some others who had no idea what was going on.
PSiu89449
writes:
>Not exactly correct. The number and frequency of resonances (standing
>waves) are fixed below about 300 Hz in a "small room". Small means
>less than 10,000 cubic feet generally. A corner speaker will excite
>the maximum number possible...which is why it gives smoother
>frequency response. There are standing waves at EVERY frequency but
>above 300 hz or so they are closely spaced and thus the sound energy
>is evenly distributed in the room. At low frequencies when you fail
>to excite some of the modes (which occurs with non-corner placement)
>you will always roughen response.
>
>
It is a fact, for which I've stated one way or another before, that corner
subwoofer placement will excite the most resonance mode thus giving flattest
theoritical response. It is also a fact that pending on where one measures, the
location of these nulls and peaks caused by standing waves are dictated by this
given set of room and subwoofer location. However, lets visualize
hypothetically that with this setup, we measured a -10dB null at 50Hz at the
listening position. To counter this, I place a subwoofer exactly at listening
position tailored to produced the exact inverse of +10dB peak at 50Hz. Wouldn't
we in effect have approximately if not exactly cancelled this measured null at
this position?
Not claiming to be an expert on this subject, but according to personal
experience and recent a Speaker Builder Magazine article, sound source in one
location will cause a set of pressure pattern across the room and at another
location will cause a different pattern. Nulls and peaks caused by standing
waves still remains, but judicial placement and setup will nullify this effect
at the listening position. Furthermore, I would like to stress the fact that
I'm mainly considering the one listening position.
>IF they are not in a corner they cannot 'complement' each other in a
>way that is smoother than corner placement. There is a school of
>thought that suggests that certain a specific placement MAY produce a
>greater sense of spaciousness and better 'externalization' (less
>bass-in-the-head) but there is no question that corner placement
>always produces the most even in-room response possible in a given
>room.
In more rooms, typical sized, I care to remember, I had experienced a minimum
of one set of null at listening position between 20 to 80Hz, corner placement
inclusive. Placing a subwoofer in different positions tend to shift this null
to differrent frequencies as preceived at listening position, corner placement
inclusive. This can also be clearly demonstrated with Sitting Duck Software.
Henceforth, I often use multiple sets of subwoofers to complement each other.
Perhaps our definition of complement is different here. Your definition to me
reads reinforcing each other cycle per cycle where my definition means filling
or cancelling each other's nulls and peaks.
It should also become clear that I'm one of those who believe that a specific
placement, taking into consideration horizontal displacement angle and near
surface modulation, MAY produce a greater sense of spaciousness. To my ears and
many others, it does. But along with you and many others, it is an accepted
fact that corner placement does produce the most even in-room response.
Best Regards
Paul Siu
j...@jmasland.com
for non-critical, very low-level background music. Using an older
MacIntosh preamp and power amp combination, I've put in the Cambridge
SoundWorks Ensemble IV. For the purpose employed, the setup fulfills
the intent, however, I have a question as this is my first experience
with a satellite/sub combination.
When listening during set-up and at higher volume levels than I will
use in this room, I "experienced," in a somewhat physical sense, the
bass emanating from the sub in the corner of the room. It's not that
I "hear" the bass in that fashion, but rather that I physically
"sense" its presence to the right of the listening location...almost
as if the air pressure was slightly higher on the right side of my
body, which I suspect may be the case.
Has anyone else experienced this sensation? I'm not interested in a
critique of the system, as I'm fully cognizant of its limitations and
shortcomings, but, rather simply, input on the "physical sensation "
aspect of the locality of the sub, to the right of the listening
position.
TIA.
uh OH!
>Curtis Leeds had this to say about:
> Re: 1 or 2 subs?
>
> CL> Howard Ferstler wrote:
>
>>> The stereo localization clues and stereo sense of space is created
>>> by sounds above 100 Hz. Bass wavelengths below that range are so
>>> long that it is impossible to localize them.
>
> CL> This is mistaken - as has been indicated in prior posts in
> CL> this thread. The inherent monophonic nature of bass is a
> CL> misnomer. Repeating it endlessly won't make the assertion
> CL> true.
>
> Ok. Prove it, then. All studies and all information I have
>previously read, with the sole exception of JJ, has said that hardly
>any human beings can hear directionality below about 80Hz with pure
>test tones and NONE can hear any below 40Hz. With music and not pure
>sine waves, you'd be extremely hard pressed to hear any directional
>information at 100Hz, let alone 60Hz or 80Hz.
What JJ was referring to was not localization, but the perception of
space, which is related, but not the same. It's not that stereo subs
are necessary to hide the location of the subwoofer, but that they're
necessary to reap the full spatial information of recordings that have
small phase shifts between channels in the lower range.
>
> While it's true that bass can contain stereo information and you
>can reproduce this stereo information in your room with 2 subwoofers,
>it's also true that you cannot hear this stereo spatial information
>below 80Hz.
Maybe you haven't noticed it before, but that doesn't mean that others
can't differentiate.
I've got to throw this part in, since I always think of Tori Amos when
I think of you, (sick association I guess, take that as you will).
Since going to a few of her concerts in the last few months, where the
sound quality pretty much universally sucked, even for sound
reinforcement (I have a vendetta against her engineers) I haven't been
able to fully enjoy her latest album. I think that she should record
all of her stuff live, since the "studio" versions usually fall
ridiculously short in terms of capturing the experience of a
performance.
> When you hear directionality from low bass in music,
>you're hearing the harmonics, which are produced by the main speakers,
>not the subwoofer. If you don't believe me, just try it yourself. I
>don't know what the normally informative JJ is talking about, but I've
>done this test myself and I've read about numerous such tests. Play
>some test tones (and do take extreme care that sympathetic vibrations
>don't give it away) of pure bass tones below 80Hz with no other
>speakers playing but the subwoofer and see if you can tell which
>direction it's coming from with your eyes closed. If you can't trust
>yourself, have someone blindfold you and spin you around a few times
>in the middle of the room before they play the tones for you. See if
>you can hear any directionality at all that isn't from sympathetic
>vibrations of walls and what not.
Sine waves in general are hard to localize. My own experience is that
even without the ability to localize, a single subwoofer run to 80 Hz
might not have lopsided the soundstage, but lacked the same degree of
convincingness. You do bring up a good point about harmonics, to
which we might want to address the matter of how steep of a slope
would be necessary to satisfy the requirements of a test anyway, and
would the resultant phase shift (translating to a significant group
delay at low frequencies) be acceptable if the slope were not
implemented in the digital domain?
PSiu89449
>When listening during set-up and at higher volume levels than I will
>use in this room, I "experienced," in a somewhat physical sense, the
>bass emanating from the sub in the corner of the room. It's not that
>I "hear" the bass in that fashion, but rather that I physically
>"sense" its presence to the right of the listening location...almost
>as if the air pressure was slightly higher on the right side of my
>body, which I suspect may be the case.
The Cambridge SoundWorks Ensemble IV's woofer is cross at a relatively high
frequency. I think it is around 150Hz. Frequencies this high will naturally
give away its presences. The best way to setup this system for image and
staging is to have have the woofer midway between two satellite. Unfortunately,
it will sacrifice the much needed corner reinforcement. But for the sole
purpose of non-critical music, it really doesn't matter. Just enjoy the music.
Best Regards
Paul Siu
PSiu89449
>Ok. Prove it, then. All studies and all information I have
>previously read, with the sole exception of JJ, has said that hardly
>any human beings can hear directionality below about 80Hz with pure
>test tones and NONE can hear any below 40Hz. With music and not pure
>sine waves, you'd be extremely hard pressed to hear any directional
>information at 100Hz, let alone 60Hz or 80Hz.
Music is transient in nature, not constant rate and pure as in controlled test
tones. Wonder if the above mentioned "All studies and all information" includes
impulse noise.
>If you don't believe me, just try it yourself. I
>don't know what the normally informative JJ is talking about, but I've
>done this test myself and I've read about numerous such tests. Play
>some test tones (and do take extreme care that sympathetic vibrations
>don't give it away) of pure bass tones below 80Hz with no other
>speakers playing but the subwoofer and see if you can tell which
>direction it's coming from with your eyes closed.
Please kindly point me to a real subwoofer and real room that is totally free
of "sympathetic vibrations" and I'll buy them. As stated before, have you or
anyone out there had a chance to do this test under dynamic transient
conditions? Given the chance to propagate and equalize, steady state pure tones
are near impossible to locate at low or very high frequencies. But since music
is transient in nature, it is much more accurate to conduct these test using
transient noise.
>>I see, and if they are 10' apart, and they contain non-in-phase
>>information, does that mean, then, that DESPITE that not in phase
>>information, the positive zero-crossings of the waveform will STILL
>>be in the same place to within under .1 millisecond? Yes or no? If
>>your answer is 'no', then who's head are you using? If the answer is
>>'yes' then how can you deal with known timing of the human auditory
>>system?
JJ is very informative and know exactly what he is talking about. He is raising
the issue of phase and time to illustrate a point on human auditory system. We
can't directly locate the sound source of steady state low frequency. But
indirectly, the phase and arrival time of these frequencies does much to alter
or reinforce our natural sence to space. Henceforth, impulse noise is a better
testing instrument on this subject.
Best Regards
Paul Siu
Howard Ferstler
j...@research.att.com (jj, curmudgeon and tiring philalethist) wrote:
> In article <6v2ps0$2...@news01.aud.alcatel.com>,
> Howard Ferstler <fer...@ibm.net> wrote:
> >If they are honest with themselves, they will hear no differences,
> >except that the subs in the corner will produce a smoother output,
> Howard, don't you think this is a wee bit of a strong claim?
OK, a corner location will *usually* produce a smoother output.
Obviously, rooms may differ, and some non-corner locations will work
better than corner locations in some rooms, also possibly because of
the way the listener is interacting with standing waves. However, in
most cases, a corner offers the smoothest coupling to room
boundaries, and also allows for the most efficient subwoofer
operation.
> >and of course a stronger one at some frequencies, due to the more
> >thorough coherent reinforcement. The bass wavelenghts below 80 Hz
> >are so long that the woofers in a normal spaced pair are already
> >essentially operating as a mono subwoofer to the listener's ears, in
> >terms of directionality, whether they are next to each other or 10
> >feet apart.
> I see, and if they are 10' apart, and they contain non-in-phase
> information, does that mean, then, that DESPITE that not in phase
> information, the positive zero-crossings of the waveform will STILL
> be in the same place to within under .1 millisecond? Yes or no? If
> your answer is 'no', then who's head are you using? If the answer is
> 'yes' then how can you deal with known timing of the human auditory
> system?
What kind of "non-in-phase" information are you talking about? If
they have much of that low-bass, out-of-phase information on the
recording itself, the low bass will cancel acoustically, and that
will work against the sound being as full and rich as it should be,
no matter what kind of bass-reproducing system we have. Clearly, this
would not be the way a recording engineer would like to see things
happen. Anyway, at long wavelengths, the source will simply be non
directional, and recordings on the whole do not have all that much
out-of phase bass, particularly really low bass, below 80 Hz. If a
recording engineer consciously wanted out-of-phase bass on a
recording, he could certainly create the effect, and the result would
be a somewhat phasy effect if spaced woofers were employed, and
simple bass-cancellation artifacts with a mono sub employed. In
either case, the overall "sound" of the low bass would be attenuated.
Yeah, if we wanted to have an out-of-phase, effect on a recording,
with "spacious" bass, we could do the low bass out of phase, but
doing so would detract from the overall low-bass levels, and the
out-of-phase effect would not be all that strong. Note that you can
get plenty of out-of-phase spaciness the old-fashioned way, by simply
recording some of the higher frequencies out of phase (including the
mid bass), while leaving the low bass in phase. (Indeed, that is one
part of the stereo effect with two-channel recordings, and is also
how Dolby Surround engineers encode surround information.) Utilizing
the frequencies above the low-bass range will get you the spacious
and directional clues you require, while still allowing for full bass
down low. If you want to put the latter out of phase to further
enhance the "effect," you will mostly lose that fullness. Engineers
do not do this, because they know that the improvement is nil, and
that low bass will suffer.
Note that one other advantage to "mono" bass on a recording is that
it allows the two, full-range speakers normally employed during
playback to share the load. If the bass were shunted to one channel
only, the work load on either system's woofer would be considerably
more than it would be if both systems were handling just half the
bass. It is safer for engineers to have mono bass, because it allows
for coherent coupling of the two woofer systems normally employed.
Also, the coupling augments the bass output, so that two systems not
only sound more spacious, but they also have stronger bass, due to
the coherent coupling. Part of the "bigness" we hear in stereo,
compared to mono, is the result of this coherently augmented bass.
Interestingly, if you adjust each of three equal,
full-range-operating systems in a Dolby Pro Logic set up for equal
treble-to-bass balance (with the center speaker set to "large"), as
well as equalized in in the usual mannter in terms of overall
full-bandwidth output (done with the processor's internal noise
generator), you will get less bass with standard Dolby Surround
programs than you would if you adjusted all three for equal overall
output and ran the center in the "small" mode. This is because with
the center set at "small," the center bass is split and sent to two
woofer systems, which couple it coherently, for 3 dB more output than
if the bass (which is mono on Dolby soundtracks) was sent entirely to
the center, running full bandwidth. If you use a full-bandwidth
center, or have a center sub, you have to adjust its level 3 dB
higher than "flat," in order for it to balance the same way things
would be if you had the center set to "small" and routed the bass to
the left and right main woofers. A big, mono sub, getting all the
system bass, solves this integration problem.
Usually, when people "hear" subs (either in corner locations or at
two locations if two subs are being used), it is because (1) the sub
is (or subs are) generating spurrious harmonics that make
localization possible, (2) the crossover point is high enough (say
above 100 Hz, particularly if the LP slope is not steep) for mid-bass
artifacts to be leaking to the sub, or (3) artifacts near the sub
(knick-knacks, wall panels, etc.) are buzzing and giving a false
sense of localization. Also, if the crossover is fairly high, many
stereo effects that normally go to the satellites are routed to the
mono sub, and this further detracts from the stereo effect and proper
localization.
> Frankly, the effects are not imaging, they seem to come to me (and
> some others) as a sense of "space", rather than as an 'image' in any
> sense, but that is surely part of the stereo illusion, what?
Well, the only way to prove it is to do some tests. Try double subs,
first in locations that are close to the main speakers, and then
double them up in the corner. Make sure that the three wild cards
noted above do not intrude and skew your perceptions.
Howard Ferstler
co...@bouji.cnchost.com wrote:
> On 2 Oct 1998 05:43:05 GMT, "Gordon Gilbert" <g...@sssnet.com> wrote:
[quoted text deleted -- deb]
> > Ok. Prove it, then. All studies and all information I have
> >previously read, with the sole exception of JJ, has said that hardly
> >any human beings can hear directionality below about 80Hz with pure
> >test tones and NONE can hear any below 40Hz. With music and not pure
> >sine waves, you'd be extremely hard pressed to hear any directional
> >information at 100Hz, let alone 60Hz or 80Hz.
> What JJ was referring to was not localization, but the perception of
> space, which is related, but not the same. It's not that stereo subs
> are necessary to hide the location of the subwoofer, but that they're
> necessary to reap the full spatial information of recordings that have
> small phase shifts between channels in the lower range.
When the bass is low enough for the spaced woofers to begin to
augment each other coherently, any out-of-phase bass will cause a
reduction in bass output, due to cancellation. The so-called,
out-of-phase "bass" on recordings that we normally hear, which cause
the perceived "stereo" effects or directional clues, exists at
frequencies that are high enough for the two woofers to acoustically
not couple. Recording engineers will not normally put low-bass out of
phase on a recording, because it will cause cancellation effects that
reduce bass levels with any kind of bass-reproduction system. If you
want powerful low bass, you have to keep it in phase on both
channels. If it is in phase, going to a mono sub will make no
difference. If it is out of phase, it might enhance the stereo effect
somewhat if spaced woofers are employed, but that effect is already
plenty strong, anyway, due to out-of-phase artifacts above the
low-bass range. With either a mono sub or spaced woofers, such
out-of-phase artifacts will cut into bass impact.
uh OH!
wrote:
>In article <6v394p$b...@news01.aud.alcatel.com>,
> j...@research.att.com (jj, curmudgeon and tiring philalethist) wrote:
>
>> In article <6v2ps0$2...@news01.aud.alcatel.com>,
>> Howard Ferstler <fer...@ibm.net> wrote:
>
>> >If they are honest with themselves, they will hear no differences,
>> >except that the subs in the corner will produce a smoother output,
>
>> Howard, don't you think this is a wee bit of a strong claim?
>
>OK, a corner location will *usually* produce a smoother output.
ETC explanation of corner loading benefits...
I don't think that's what he was referring to, but rather the
presumptuous claim of what honest people will hear.
>> I see, and if they are 10' apart, and they contain non-in-phase
>> information, does that mean, then, that DESPITE that not in phase
>> information, the positive zero-crossings of the waveform will STILL
>> be in the same place to within under .1 millisecond? Yes or no? If
>> your answer is 'no', then who's head are you using? If the answer is
>> 'yes' then how can you deal with known timing of the human auditory
>> system?
>
>What kind of "non-in-phase" information are you talking about? If
>they have much of that low-bass, out-of-phase information on the
>recording itself, the low bass will cancel acoustically, and that
>will work against the sound being as full and rich as it should be,
>no matter what kind of bass-reproducing system we have. Clearly, this
>would not be the way a recording engineer would like to see things
>happen. Anyway, at long wavelengths, the source will simply be non
>directional, and recordings on the whole do not have all that much
>out-of phase bass, particularly really low bass, below 80 Hz.
Omni directional speakers maintain directional information recorded on
stereo. They interact differently than uni-directional ones, but
that's a room effect, not an inter-channel phase effect. The phase
shift between channels can be maintained regardless of dispersion
patterns, even at 5 Hz.
>Yeah, if we wanted to have an out-of-phase, effect on a recording,
>with "spacious" bass, we could do the low bass out of phase, but
>doing so would detract from the overall low-bass levels,
He's talking about delays of a few milliseconds between channels, not
opposite polarity.
> Note that you can
>get plenty of out-of-phase spaciness the old-fashioned way, by simply
>recording some of the higher frequencies out of phase (including the
>mid bass), while leaving the low bass in phase. (Indeed, that is one
>part of the stereo effect with two-channel recordings, and is also
>how Dolby Surround engineers encode surround information.)
As I recall, they only phase shift the surround encoding by about 90
degrees, so that there is no cancellation occuring when put to mono,
but rather a failure to constructively interfere.
> If you want to put the latter out of phase to further
>enhance the "effect," you will mostly lose that fullness. Engineers
>do not do this, because they know that the improvement is nil, and
>that low bass will suffer.
The effect that he's referring to occurs within the recording venue.
I wouldn't group the motives of recording engineers into a single
category, as they tend to differ widely, just like consumer
preference.
>Note that one other advantage to "mono" bass on a recording is that
>it allows the two, full-range speakers normally employed during
>playback to share the load. If the bass were shunted to one channel
>only, the work load on either system's woofer would be considerably
>more than it would be if both systems were handling just half the
>bass. It is safer for engineers to have mono bass, because it allows
>for coherent coupling of the two woofer systems normally employed.
I think that JJ is involved in professional recording in some regard,
and simply chooses to make recordings that aren't limited by
considerating the requirements of a boombox. He's not suggesting that
bass be put out of phase, or put to one channel, but that there are
audible benefits to maintaining stereo information of low frequencies,
mostly slight phase shifts between channels, which don't cause
significant cancellation as opposed to monofied bass from the same
speakers.
>> Frankly, the effects are not imaging, they seem to come to me (and
>> some others) as a sense of "space", rather than as an 'image' in any
>> sense, but that is surely part of the stereo illusion, what?
>
>Well, the only way to prove it is to do some tests. Try double subs,
>first in locations that are close to the main speakers, and then
>double them up in the corner. Make sure that the three wild cards
>noted above do not intrude and skew your perceptions.
Not valid, as they will inevitably change the room response. He'd
have to monofy the bass via DSP, and run the same speaker array, and
compare the two. Given that he's run FIR filter tests, I think he's
been there, done that. I could always be wrong, though.
uh OH!
wrote:
>In article <6v5r1j$9jn$1...@agate.berkeley.edu>,
> co...@bouji.cnchost.com wrote:
>> On 2 Oct 1998 05:43:05 GMT, "Gordon Gilbert" <g...@sssnet.com> wrote:
>When the bass is low enough for the spaced woofers to begin to
>augment each other coherently, any out-of-phase bass will cause a
>reduction in bass output, due to cancellation.
We're not talking about out of phase, we're talking in the
milliseconds here, which is far from enough to cause a phase shift
greater than 90 degrees, which is required to cause cancellation.
> Recording engineers will not normally put low-bass out of
>phase on a recording
Of course they won't intentionally cause phase inversion between the
two channels, but they won't necessarily sum content to one channel
and then split it if it contains stereo information. The majority of
them may, but the majority of them don't seem interested in good
recordings, or at least the producers don't, because 99% of all
recordings (being rather generous here) suck in terms of spatial cues.
They're flat, and lifeless for the most part. I'm not saying that
studio recordings have to be bad, but that they usually are, and using
the practices of those who create mediocre work as evidence isn't
evidence at all.
uh OH!
>In article <6uu2o2$t7r$1...@agate.berkeley.edu>,
> cle...@idt.net wrote:
>> Howard Ferstler wrote:
>> This is mistaken - as has been indicated in prior posts in
>> this thread. The inherent monophonic nature of bass is a
>> misnomer. Repeating it endlessly won't make the assertion
>> true.
>How are we going to prove this?
>If a person listens to two full-range speakers and uses what they
>hear coming from them to determine that "stereo" effects exist in the
>low bass, then they are going about it all wrong. They should set up
>two subwoofers, crossing over at below 100 Hz (or better yet, at the
>more typical 80 Hz), under two satellites, and then listen to a
>number of stereo recordings. Then, they should move both of the subs
>to a corner off to the sides and listen again.
Nope, since that will change the frequency response, and would most
likely be audible simply by that.
>If they are honest with themselves, they will hear no differences,
>except that the subs in the corner will produce a smoother output,
>and of course a stronger one at some frequencies, due to the more
>thorough coherent reinforcement.
That would be a difference, wouldn't it? Perhaps better in some ways,
and perhaps a minor compromise.
> The bass wavelenghts below 80 Hz
>are so long that the woofers in a normal spaced pair are already
>essentially operating as a mono subwoofer to the listener's ears, in
>terms of directionality,
Really? I thought that the spacing of the ears limited the experience
of the phase shift. A pair of subs 20 feet apart could certainly
maintain the directionality of stereo bass. The question is the
nature of the perception in the listener.
> whether they are next to each other or 10
>feet apart.
Even then, I can't think why not, so long as you're not sitting 20
feet away.
>Interestingly, however, the spacing between two woofer systems that
>far apart will result in a suckout effect (basically, the "Allison
>Effect" operating at lower frequencies and between woofer systems,
>rather than between a woofer and a large, reflective boundary) at a
>frequency that will be determined by the spacing between the woofer
>systems. This will result in a notch at a certain frequency. For
>example, with a 12-foot spacing, the listener will get a notch at
>about 56 Hz. If there is also a large room boundary (or boundaries)
>at a distance equal to half that between the woofers (if either or
>both are 6 feet from a wall, for instance), the notch will be
>compounded by additional of these quarter-wavelength cancellation
>effects. Note that these effects are unrelated to standing-wave
>artifacts, and so cannot be eliminated by moving the listening
>position. They are power-input related and not
>boundary-reinforcement related.
If you put them in opposite corners, say for your example, 12 feet
away, since their output falls off exponentially if you're not taking
room boundary induced mode "standing wave artifacts" into
consideration, how deep will this notch be when the wave from one
woofer has decayed substantially relative to the output of another?
I'm not arguing that it's more difficult to setup multiple subs, only
that it's not necessarily a disaster in terms of frequency response,
especially if you've got the ability to slightly EQ the bass range.
>Anyway, a mono sub, placed in a corner, eliminates this problem, and
>because there is no problem with stereo bass below 80-100 Hz to begin
>with, the solution does not cause havoc with the sense of stereo
>bass.
So you claim, and others claim differently. I wouldn't call a mono
subwoofer havoc, but it is a practical compromise that usually obtains
significant benefits at the cost of ultimate reproduction. If you've
tried stereo subs and you didn't like it, don't use them.
>Another interesting point is that stereo bass, below 80-100 Hz does
>not ordinarily exist as an audible phenomonon on recordings, anyway.
The key to that statement is audible, which is what this whole thing
is about.
>Yes, some spaced-microphone recordings with really wide microphone
>placement (certain Telarc recordings, and possibly recordings made
>with the Decca Tree) might have a bit of stereo bass at 60-80 Hz,
and why not at 40 Hz?
>and
>so, theoreticaly, might multi-microphone recordings of rock music,
>and the like, although this is rarely the case, because the bass is
>usually mixed to mono for convenience sake. However, no coincident
>(Blumlein) or near-coincident (ORTF or NOS) recording will contain
>stereo low bass in any way, shape, or form.
That might be reason not to use those techniques then, eh? So, even if
full-system
>woofers or double subwoofers could reproduce "stereo" low bass (which
>I will reiterate, they really cannot),
Why?
> with most purist recordings
>there is no stereo bass to reproduce. Also, all bass on LP
>recordings is mixed to mono, as a matter of policy.
Maybe the LP artifacts add stereo information, I dunno.
>I have listened to mono subs with the crossover set to about 150 Hz,
>and it was possible to clearly localize the subwoofer and the
>phenomenon was rather disconcering. However, with the crossover set
>to 100 Hz or lower, and with a decently steep LP slope, you simply
>cannot detect localization clues with a mono subwoofer.
So you're saying that a very audible problem simply disappears in 1/2
of an octave. Wow. I could buy that with harmonic distortion at 8
kHz vs 12 kHz, but we're still within a healty margin of the audible
range. Why do you think that is?
> Another way
>to see how much stereo there is in low bass is to utilize a Dolby
>Surround decoder. Set up a sub on the center channel, or use a big
>center speaker with a big woofer, switch the center to
>full-bandwidth, turn on the DPL decoder, and notice how much bass
>comes from the center. The DPL circuitry will steer all mono signals
>to the center, and the vast bulk of the bass will be coming out of
>the center sub. The other bass drivers in the system will only be
>reproducing upper bass. The low stuff is steered to the center,
>because it is mostly mono.
And the slope and steering is poor, pulling information well above 100
Hz around between the mains and center. I see your point, but even
disregarding the differences in FR due to room placement differences
between the center and L/R speakers, that's a lousy test. With three
identical speakers which got down to the lower thirties, I did this
with DPL on music and the difference was far more obvious than the
stereo presence of bass by itself.
>I will also note that the people who build mono subs are not jerks,
I haven't been following this thread closely for awhile, as not much
new has come up since JJ explained exactly what he was getting at in
the rather civil discussion with Tom (mr. Nousaine since I don't
really feel like I know him, as if I really know JJ from all his
postings.) Who said that people who build, or use mono subs are
jerks. Using a mono subwoofer to obtain a given goal might be
considered intelligent.
>and they have researched this phenomenon plenty.
I've not seen it in real scientific journals, though I stopped
browsing the psychology database after I left school. I've seen
articles in audio magazines, but I've never seen real scientific
anything in audio magazines, so I wouldn't criticize those articles.
>The only advantage
>to dual subs is increased output,
So you say and believe, though others may not. It is possible, I
guess, that those who think that stereo bass can exist, and can be
perceived, are just gearheads clinging to a placebo, though the word
of a scientist who studies audible perception without an agenda does
kind of tilt my inclination to believe that the possible benefits of
stereo subs aren't just another of my hallucinations.
> and the listener will get even
>better results with dual units if you stack them together in the
>corner.
As far as output, absolutely. Nobody said that stereo subs didn't
have any compromises either.
Howard Ferstler
co...@bouji.cnchost.com wrote:
> On 4 Oct 1998 17:33:14 GMT, Howard Ferstler <fers...@yahoo.com>
> wrote:
> >In article <6v394p$b...@news01.aud.alcatel.com>,
> > j...@research.att.com (jj, curmudgeon and tiring philalethist) wrote:
> >> In article <6v2ps0$2...@news01.aud.alcatel.com>,
> >> Howard Ferstler <fer...@ibm.net> wrote:
> >> >If they are honest with themselves, they will hear no differences,
> >> >except that the subs in the corner will produce a smoother output,
> >> Howard, don't you think this is a wee bit of a strong claim?
> >OK, a corner location will *usually* produce a smoother output.
> ETC explanation of corner loading benefits...
> I don't think that's what he was referring to, but rather the
> presumptuous claim of what honest people will hear.
Well, I think a lot of high enders are less than honest with themselves.
Delusion tends to drive the industry.
> >> I see, and if they are 10' apart, and they contain non-in-phase
> >> information, does that mean, then, that DESPITE that not in phase
> >> information, the positive zero-crossings of the waveform will STILL
> >> be in the same place to within under .1 millisecond? Yes or no? If
> >> your answer is 'no', then who's head are you using? If the answer is
> >> 'yes' then how can you deal with known timing of the human auditory
> >> system?
> >What kind of "non-in-phase" information are you talking about? If
> >they have much of that low-bass, out-of-phase information on the
> >recording itself, the low bass will cancel acoustically, and that
> >will work against the sound being as full and rich as it should be,
> >no matter what kind of bass-reproducing system we have. Clearly, this
> >would not be the way a recording engineer would like to see things
> >happen. Anyway, at long wavelengths, the source will simply be non
> >directional, and recordings on the whole do not have all that much
> >out-of phase bass, particularly really low bass, below 80 Hz.
> Omni directional speakers maintain directional information recorded on
> stereo. They interact differently than uni-directional ones, but
> that's a room effect, not an inter-channel phase effect. The phase
> shift between channels can be maintained regardless of dispersion
> patterns, even at 5 Hz.
In the bass range, I was under the assumption that all speakers were
omnidirectional, except for dipoles. Do we hear that phase shift?
> >Yeah, if we wanted to have an out-of-phase, effect on a recording,
> >with "spacious" bass, we could do the low bass out of phase, but
> >doing so would detract from the overall low-bass levels,
> He's talking about delays of a few milliseconds between channels, not
> opposite polarity.
Is this audible at frequencies below 80 Hz?
> > Note that you can
> >get plenty of out-of-phase spaciness the old-fashioned way, by simply
> >recording some of the higher frequencies out of phase (including the
> >mid bass), while leaving the low bass in phase. (Indeed, that is one
> >part of the stereo effect with two-channel recordings, and is also
> >how Dolby Surround engineers encode surround information.)
> As I recall, they only phase shift the surround encoding by about 90
> degrees, so that there is no cancellation occuring when put to mono,
> but rather a failure to constructively interfere.
Identical signals are shifted plus 90 degrees in one channel and minus 90
degrees in the other, for a total difference of 180 degrees. The steering
supposedly ignores all other phase differences, but I suppose the quality of
differentiation will vary. The steering is supposed to ignore simple
difference signals that would be routed with a simple L-R, Hafler-like
circuit. There is complete cancellation of the surround channels with mono
playback.
> > If you want to put the latter out of phase to further
> >enhance the "effect," you will mostly lose that fullness. Engineers
> >do not do this, because they know that the improvement is nil, and
> >that low bass will suffer.
> The effect that he's referring to occurs within the recording venue.
> I wouldn't group the motives of recording engineers into a single
> category, as they tend to differ widely, just like consumer
> preference.
I'll agree, here. I have a relatively knowledgeable engineer available that I
can discuss this with, and hope to get back with you on this one.
> >Note that one other advantage to "mono" bass on a recording is that
> >it allows the two, full-range speakers normally employed during
> >playback to share the load. If the bass were shunted to one channel
> >only, the work load on either system's woofer would be considerably
> >more than it would be if both systems were handling just half the
> >bass. It is safer for engineers to have mono bass, because it allows
> >for coherent coupling of the two woofer systems normally employed.
> I think that JJ is involved in professional recording in some regard,
> and simply chooses to make recordings that aren't limited by
> considerating the requirements of a boombox. He's not suggesting that
> bass be put out of phase, or put to one channel, but that there are
> audible benefits to maintaining stereo information of low frequencies,
> mostly slight phase shifts between channels, which don't cause
> significant cancellation as opposed to monofied bass from the same
> speakers.
There is no doubt that those phase shifts, other than possibly reducing
output a bit, would not be audible with a mono sub. The question is: if they
are there below 80 Hz, would reproducing them over a pair of woofers make
them audible, particularly when we take into consideration all the masking
effects of frequencies above the bass range? Also, with dual subs we have
the suckout cancellations that I mentioned previously (related to the Allison
Effect). It is possible that what some people hear with dual subs is related
to the cancellation nulls that two subs will generate when playing identical
signals.
> >> Frankly, the effects are not imaging, they seem to come to me (and
> >> some others) as a sense of "space", rather than as an 'image' in any
> >> sense, but that is surely part of the stereo illusion, what?
> >Well, the only way to prove it is to do some tests. Try double subs,
> >first in locations that are close to the main speakers, and then
> >double them up in the corner. Make sure that the three wild cards
> >noted above do not intrude and skew your perceptions.
> Not valid, as they will inevitably change the room response. He'd
> have to monofy the bass via DSP, and run the same speaker array, and
> compare the two. Given that he's run FIR filter tests, I think he's
> been there, done that. I could always be wrong, though.
Well, the corner would reinforce at certain frequencies, as would the
proximity of the subs when that close to each other, but once the levels were
re-adjusted, we could still at least listen for the stereo effects. I think
you are making the comparison more complex than it needs to be.
Howard Ferstler
Howard Ferstler
> >In article <6uu2o2$t7r$1...@agate.berkeley.edu>,
> > cle...@idt.net wrote:
> >> Howard Ferstler wrote:
> >> This is mistaken - as has been indicated in prior posts in
> >> this thread. The inherent monophonic nature of bass is a
> >> misnomer. Repeating it endlessly won't make the assertion
> >> true.
> >How are we going to prove this?
> >If a person listens to two full-range speakers and uses what they
> >hear coming from them to determine that "stereo" effects exist in the
> >low bass, then they are going about it all wrong. They should set up
> >two subwoofers, crossing over at below 100 Hz (or better yet, at the
> >more typical 80 Hz), under two satellites, and then listen to a
> >number of stereo recordings. Then, they should move both of the subs
> >to a corner off to the sides and listen again.
> Nope, since that will change the frequency response, and would most
> likely be audible simply by that.
Well, it would change the FR, but I think that if you adjust the balance
properly (with the level controls on the subs, or on the processor, it does
not matter) you will at least have response that was as smooth as before, and
probably a bit smoother. I do not see how we can run into problems with
hearing stereo low bass if the the FR is slightly different down really low.
That might make things a bit more difficult, but if stereo bass is as strong
a factor as some people say, we should be able to detect it, even if corner
placement of the two subs improves smoothness, which it most likely will do.
What we are looking for is proof not only that a mono sub in a corner is not
going to screw up the stereo effect and spaciousness, but that it will make
the overall sound better. So, if we follow the guidelines I outlined, we will
be able to not only determine if a loss in stereo low bass is a non problem,
but will also be able to determine (after the levels are adjusted) if a
corner-located bass source is just plain better sounding. Part of this will
result, I believe, in the elimination of the cancellation suckout that should
always happen when spaced woofer systems, particularly if those spaced
woofers are not in corners, are in operation.
> >If they are honest with themselves, they will hear no differences,
> >except that the subs in the corner will produce a smoother output,
> >and of course a stronger one at some frequencies, due to the more
> >thorough coherent reinforcement.
> That would be a difference, wouldn't it? Perhaps better in some ways,
> and perhaps a minor compromise.
Yes, and it will prove that a corner-position subwoofer will result in better
sound than spaced dual subs or spaced full-range speakers.
> > The bass wavelenghts below 80 Hz
> >are so long that the woofers in a normal spaced pair are already
> >essentially operating as a mono subwoofer to the listener's ears, in
> >terms of directionality,
> Really? I thought that the spacing of the ears limited the experience
> of the phase shift. A pair of subs 20 feet apart could certainly
> maintain the directionality of stereo bass. The question is the
> nature of the perception in the listener.
Well, this is what my "test" was supposed to determine. I have not heard
"stereo" low bass, myself. I have heard stereo middle bass, though.
> > whether they are next to each other or 10
> >feet apart.
> Even then, I can't think why not, so long as you're not sitting 20
> feet away.
I am not sure what this means. Speakers spaced that far apart will be
coupling coherently below a certain frequency. They will be cancelling and
creating a null at a different one. A mono sub eliminates such artifacts.
> >Interestingly, however, the spacing between two woofer systems that
> >far apart will result in a suckout effect (basically, the "Allison
> >Effect" operating at lower frequencies and between woofer systems,
> >rather than between a woofer and a large, reflective boundary) at a
> >frequency that will be determined by the spacing between the woofer
> >systems. This will result in a notch at a certain frequency. For
> >example, with a 12-foot spacing, the listener will get a notch at
> >about 56 Hz. If there is also a large room boundary (or boundaries)
> >at a distance equal to half that between the woofers (if either or
> >both are 6 feet from a wall, for instance), the notch will be
> >compounded by additional of these quarter-wavelength cancellation
> >effects. Note that these effects are unrelated to standing-wave
> >artifacts, and so cannot be eliminated by moving the listening
> >position. They are power-input related and not
> >boundary-reinforcement related.
> If you put them in opposite corners, say for your example, 12 feet
> away, since their output falls off exponentially if you're not taking
> room boundary induced mode "standing wave artifacts" into
> consideration, how deep will this notch be when the wave from one
> woofer has decayed substantially relative to the output of another?
> I'm not arguing that it's more difficult to setup multiple subs, only
> that it's not necessarily a disaster in terms of frequency response,
> especially if you've got the ability to slightly EQ the bass range.
The notch would be only a few dB deep. The problem gets serious when a pair
of woofers are, say, 12-feet apart, along a wall or out in front of it, and
each woofer center is also 6 feet (a distance equal to half that between the
woofers), or so, from either a side wall or the front wall. This would double
up the cancellation artifacts. With very wide-spaced subs, or dual subs in
two corners, the effect would be rather minimal, I think. Note that I use
two subs, myself, located in corners 22 feet apart, along the front wall of
my big listening room, but have one dealing only with the center-channel bass
and the other dealing with everything else, including LFE on Dolby Digital.
Thus, they really do not deal simultanerously with equal-strength, mono-bass
signals.
> >Anyway, a mono sub, placed in a corner, eliminates this problem, and
> >because there is no problem with stereo bass below 80-100 Hz to begin
> >with, the solution does not cause havoc with the sense of stereo
> >bass.
> So you claim, and others claim differently. I wouldn't call a mono
> subwoofer havoc, but it is a practical compromise that usually obtains
> significant benefits at the cost of ultimate reproduction. If you've
> tried stereo subs and you didn't like it, don't use them.
Well, we differ dramatically, here. I do not consider it a compromise at all.
I consider two full-range speakers, without a sub, as the compromise. Also,
stereo subs are not going to be a disaster, but a big mono unit will work a
little bit better in terms of smoothing out the low bass, and will see to it
that no suckout notches can form.
> >Another interesting point is that stereo bass, below 80-100 Hz does
> >not ordinarily exist as an audible phenomonon on recordings, anyway.
> The key to that statement is audible, which is what this whole thing
> is about.
Correct. Obviously, it will be difficult whether stereo low bass really
exists in significant enough amounts to matter.
> >Yes, some spaced-microphone recordings with really wide microphone
> >placement (certain Telarc recordings, and possibly recordings made
> >with the Decca Tree) might have a bit of stereo bass at 60-80 Hz,
> and why not at 40 Hz?
The spacing is not wide enough.
> >and
> >so, theoreticaly, might multi-microphone recordings of rock music,
> >and the like, although this is rarely the case, because the bass is
> >usually mixed to mono for convenience sake. However, no coincident
> >(Blumlein) or near-coincident (ORTF or NOS) recording will contain
> >stereo low bass in any way, shape, or form.
> That might be reason not to use those techniques then, eh? So, even if
> full-system
Not if it is not audible.
> >woofers or double subwoofers could reproduce "stereo" low bass (which
> >I will reiterate, they really cannot),
>
> Why?
Because they couple coherently, with the frequencies dependend on the spacing.
> > with most purist recordings
> >there is no stereo bass to reproduce. Also, all bass on LP
> >recordings is mixed to mono, as a matter of policy.
> Maybe the LP artifacts add stereo information, I dunno.
Possibly. Certainly they do at higher frequencies. As I have noted in other
posts, audio is essentially fake, anyway, and the phase artifacts generated
by the LP record may actually positively enhance that fakeness with some
recording techniques and with some audio systems. My main objection to the
LP involves other artifacts, but that is a subject that is different from
what we are dealing with here.
> >I have listened to mono subs with the crossover set to about 150 Hz,
> >and it was possible to clearly localize the subwoofer and the
> >phenomenon was rather disconcering. However, with the crossover set
> >to 100 Hz or lower, and with a decently steep LP slope, you simply
> >cannot detect localization clues with a mono subwoofer.
> So you're saying that a very audible problem simply disappears in 1/2
> of an octave. Wow. I could buy that with harmonic distortion at 8
> kHz vs 12 kHz, but we're still within a healty margin of the audible
> range. Why do you think that is?
I heard it. It was easy to notice. Indeed, I was under the impression that
150 Hz was high enough to mask the effect, until I stacked both woofers in
the corner and heard the weird, midbass soundstage shift. However, with both
my Velodyne F1800 and FSR-12, plus the Hsu Reseach, Paradigm, B&W, and
Atlantic Technology subs I have been fooling with lately for review purposes,
I heard no artifacts when the LP was set to 100 Hz, or lower. At 100 Hz,
however, the LP slope needs to be pretty steep, which is why 80 Hz is a
better bet. A Hsu TN1220 I tested (and now own) has a 91-Hz crossover and 24
dB slopes, and I hear no problem artifacts from the woofer, whatsoever.
> > Another way
> >to see how much stereo there is in low bass is to utilize a Dolby
> >Surround decoder. Set up a sub on the center channel, or use a big
> >center speaker with a big woofer, switch the center to
> >full-bandwidth, turn on the DPL decoder, and notice how much bass
> >comes from the center. The DPL circuitry will steer all mono signals
> >to the center, and the vast bulk of the bass will be coming out of
> >the center sub. The other bass drivers in the system will only be
> >reproducing upper bass. The low stuff is steered to the center,
> >because it is mostly mono.
> And the slope and steering is poor, pulling information well above 100
> Hz around between the mains and center. I see your point, but even
> disregarding the differences in FR due to room placement differences
> between the center and L/R speakers, that's a lousy test. With three
> identical speakers which got down to the lower thirties, I did this
> with DPL on music and the difference was far more obvious than the
> stereo presence of bass by itself.
You need to watch what happens when you switch from the small to the large
mode with the center. With the large mode, the bass is routed nearly
entirely to the center. With the small mode, it is split and sent to the
mains, but at lower frequencies they couple coherently, and the low-bass
levels are higher than with the center-large mode.
> >I will also note that the people who build mono subs are not jerks,
> I haven't been following this thread closely for awhile, as not much
> new has come up since JJ explained exactly what he was getting at in
> the rather civil discussion with Tom (mr. Nousaine since I don't
> really feel like I know him, as if I really know JJ from all his
> postings.) Who said that people who build, or use mono subs are
> jerks. Using a mono subwoofer to obtain a given goal might be
> considered intelligent.
Well, the implication is that most subwoofer companies build mono subs, and
because they want satisfied customers they would not be about to produce
designs that were detrimental to high fidelity sound reproduction. Yes, some
make the option for dual subs, but that usually involves a need for more
output power, not stereo low bass.
> >and they have researched this phenomenon plenty.
> I've not seen it in real scientific journals, though I stopped
> browsing the psychology database after I left school. I've seen
> articles in audio magazines, but I've never seen real scientific
> anything in audio magazines, so I wouldn't criticize those articles.
I would think that customer satisfaction would lead them to produce the best
products possible, particularly when you get into top models like those
produced by Paradigm, Hsu, and Velodyne. Their flagship systems are all
mono.
> >The only advantage
> >to dual subs is increased output,
> So you say and believe, though others may not. It is possible, I
> guess, that those who think that stereo bass can exist, and can be
> perceived, are just gearheads clinging to a placebo, though the word
> of a scientist who studies audible perception without an agenda does
> kind of tilt my inclination to believe that the possible benefits of
> stereo subs aren't just another of my hallucinations.
Properly placed, they certainly cannot do a lot of harm, and if they are
spaced enough, they will only augment each other conerently at really low
frequencies. That can result in a perception of stronger very low bass,
behond what would occur with only one sub of the same design. The big
problem, ironically, involves spaced full-range speakers, which really can
exhibit suckout notches in the bass range, if their distances to room
boundaries is half that of the distance between them.
> > and the listener will get even
> >better results with dual units if you stack them together in the
> >corner.
> As far as output, absolutely. Nobody said that stereo subs didn't
> have any compromises either.
Stacking them, of course, usually creates an eyesore, which is why I prefer a
single big unit. As I have noted before, I do use two big subs, but each
handles decidedly different bass material. When I listen to DD material, my
center sub hardly works at all, and when I listen to stereo material, it is
off completely. When I listen to DPL material, the center sub does most of
the work, and the other sub, which handles all the other channels, produces
little bass, and negligible low bass.
Howard Ferstler
co...@bouji.cnchost.com wrote:
> On 4 Oct 1998 17:33:23 GMT, Howard Ferstler <fers...@yahoo.com>
> wrote:
> >In article <6v5r1j$9jn$1...@agate.berkeley.edu>,
> > co...@bouji.cnchost.com wrote:
> >> On 2 Oct 1998 05:43:05 GMT, "Gordon Gilbert" <g...@sssnet.com> wrote:
> >When the bass is low enough for the spaced woofers to begin to
> >augment each other coherently, any out-of-phase bass will cause a
> >reduction in bass output, due to cancellation.
> We're not talking about out of phase, we're talking in the
> milliseconds here, which is far from enough to cause a phase shift
> greater than 90 degrees, which is required to cause cancellation.
I honestly find it hard to believe that phase shifts in the
millisecond range will be audible with stereo program material, given
the overwhelming masking effects of the stereo frequencies above the
low-bass range.
> > Recording engineers will not normally put low-bass out of
> >phase on a recording
> Of course they won't intentionally cause phase inversion between the
> two channels, but they won't necessarily sum content to one channel
> and then split it if it contains stereo information. The majority of
> them may, but the majority of them don't seem interested in good
> recordings, or at least the producers don't, because 99% of all
> recordings (being rather generous here) suck in terms of spatial cues.
> They're flat, and lifeless for the most part. I'm not saying that
> studio recordings have to be bad, but that they usually are, and using
> the practices of those who create mediocre work as evidence isn't
> evidence at all.
The problem is not the recordings or the engineers, per se. It
involves the limintations of two-channel audio - or any audio system
that depends on a few channels up front to deliver spatial clues for
any kind of ensemble performing out front. Adding a center solves
some problems, particularly concerning the need for a well-focussed
soloist in the center, but all high-fidelity sound reproduction is
essentially fake. We have to live with that one. The question is:
does stereo sound in the deep-bass range have any impact on
spatiality or the fake sense of stereo that we are stuck with, when
it comes to two or three channels up front? I think the masking
effects of the multitude of signals above the lower-bass range
absolutely negate any subtle effects of stereo low bass.
Howard Ferstler
jj, curmudgeon and tiring philalethist
Howard Ferstler <fers...@yahoo.com> wrote:
>What kind of "non-in-phase" information are you talking about? If
>they have much of that low-bass, out-of-phase information on the
>recording itself, the low bass will cancel acoustically, and that
>will work against the sound being as full and rich as it should be,
Why would you ever make this claim, Howard? A .8 millisecond phase
difference will make nearly ZERO cancellation.
Again, can you get down to the same positive-going cycle of the sine
wave to the ear within .1 milliseconds with 1 sub vs. 2?
Yes or no?
jj, curmudgeon and tiring philalethist
uh OH! <co...@bouji.cnchost.com> wrote:
>I think that JJ is involved in professional recording in some regard,
>and simply chooses to make recordings that aren't limited by
>considerating the requirements of a boombox.
Actually, I've just started doing that again, after a 20+ year hiatus
doing other research, but this subwoofer experience is supported by
more than the last half-year.
Consider, all, the inter-aural time delay.
>He's not suggesting that
>bass be put out of phase, or put to one channel, but that there are
>audible benefits to maintaining stereo information of low frequencies,
>mostly slight phase shifts between channels, which don't cause
>significant cancellation as opposed to monofied bass from the same
>speakers.
Especially so that they remain attached to the same accoustic event
that generated them. No, this is not an easy thing to measure.
HOWARD W FERSTLER
> In article <6v8bgq$f...@news01.aud.alcatel.com>,
> Howard Ferstler <fers...@yahoo.com> wrote:
> >What kind of "non-in-phase" information are you talking about? If
> >they have much of that low-bass, out-of-phase information on the
> >recording itself, the low bass will cancel acoustically, and that
> >will work against the sound being as full and rich as it should be,
> Why would you ever make this claim, Howard? A .8 millisecond phase
> difference will make nearly ZERO cancellation.
> Again, can you get down to the same positive-going cycle of the sine
> wave to the ear within .1 milliseconds with 1 sub vs. 2?
> Yes or no?
I am not sure what you are driving at, here. You appear to believe
that a very-low-bass phase shift in that category will be audible,
and will have an impact on the depth, imaging, localization,
soundstaging, and spaciousness of a recording. However, I believe
that while stereo low bass might have audible effects if it were
listened to alone, when all the other materials on a recording, above
the low-bass range, add their multitide of stereo effects, the stereo
impact of low bass phase shift on the sense of spaciousness and
stereophony is pretty much swamped.
The bottom line is that I have never heard the effect with musical or
home-theater program material. Some claim to have heard it, but
there are a multitude of other variables involved that make it
difficult to sort out what is causing the subjectively perceived
differences, not the least of which are the possible prejudices of
some of those who see that single sub sitting in the corner, and let
their eyes run the show.
Howard Ferstler
hfer...@ibm.net
jj, curmudgeon and tiring philalethist
Howard Ferstler <fers...@yahoo.com> wrote:
>I honestly find it hard to believe that phase shifts in the
>millisecond range will be audible with stereo program material, given
>the overwhelming masking effects of the stereo frequencies above the
>low-bass range.
DOWNWARD MASKING? Unh, Howard, masking goes UPWARDS, not downwards.
In particular, the steepness of the slope of the highpass part of the
first few critical bands is the kind of steepness you can only get
with transmission line filters. More to the point, there is at least
40dB of attenuation for 50Hz from stimulation at 150Hz, and more than
90 from 50Hz with the masking stimulation at 300Hz.
Please read more about the spread of masking, there is a really good
reason it's called UPwards spread of masking.
>Adding a center solves
>some problems, particularly concerning the need for a well-focussed
>soloist in the center, but all high-fidelity sound reproduction is
>essentially fake.
Adding a center does a lot more than that. Fletcher, chapter 13.
Read and enjoy, with program material none the less.
>We have to live with that one.
I disagree. I think we should be moving to (real) multichannel as
fast as we can run. It's no longer even hard to get multichannel
delivery with the onset of things like MPEG-AAC, even running at huge
bit rates for huge safety margins.
>I think the masking
>effects of the multitude of signals above the lower-bass range
>absolutely negate any subtle effects of stereo low bass.
What masking effects?
In general, the downward spread of masking is at least -25dB/critical
band, and more at very low frequencies. Interesting things happen
when you get well below neural firing rates.
That's compared to the upward spread of masking, which runs between
-15dB/critical band to effectively ZERO db/critical band at high
levels.
Basically, that first 100Hz is allllll the way at the end of the
cochlea where it's protected and well-filtered.
Howard Ferstler
> >I honestly find it hard to believe that phase shifts in the
> >millisecond range will be audible with stereo program material, given
> >the overwhelming masking effects of the stereo frequencies above the
> >low-bass range.
>
> DOWNWARD MASKING? Unh, Howard, masking goes UPWARDS, not downwards.
So, you are saying that the subtle phase shifts in the low bass are audible,
and will be perceived, in spite of the far stronger directional and
spatiality clues being offered by the left and right (and center, and
surround) satellites that happen to be reproducing the sound from 80 Hz on
up? Effects that most admit are just barely audible when listening to
subwoofers alone will somehow remain audible when the outputs of the
satellites, which have spatiality and directional effects that are clearly
and much more immediately audible, are factored in. OK, if you say so.
However, we also have to take into consideration the Franssen Effect, which
localizes images at the satellites, and the precidence effect, which will
play a part if the subwoofer or subwoofers happen to be further from the
listener than the satellites. We have lots of variables, here, and the least
influential one will be the status of the bass signals, in terms of stereo
effect, below about 80 Hz, or below 100 Hz if the LP filtering is steep
enough.
> In particular, the steepness of the slope of the highpass part of the
> first few critical bands is the kind of steepness you can only get
> with transmission line filters. More to the point, there is at least
> 40dB of attenuation for 50Hz from stimulation at 150Hz, and more than
> 90 from 50Hz with the masking stimulation at 300Hz.
>
> Please read more about the spread of masking, there is a really good
> reason it's called UPwards spread of masking.
So, does this limitation with downward masking apply to subtle, low-level,
low-frequency spatiality clues, as it does with the simple monophonic masking
of lower frequency sounds? We have noted that the spatiality clues from
stereo low bass are already pretty subtle, at best, because some people (me,
Nousaine, etc.) are not particularly aware of them at all. It looks like it
would not take a lot of above-80-Hz output from the satellites, given the
VERY strong directional and spatiality signals present in those systems, to
obscure those already very low-level, low-frequency spatiality artifacts you
claim are audible. If they can mask such artifacts, then a mono sub is as
good as a pair of stereo subs.
> >Adding a center solves
> >some problems, particularly concerning the need for a well-focussed
> >soloist in the center, but all high-fidelity sound reproduction is
> >essentially fake.
> Adding a center does a lot more than that. Fletcher, chapter 13.
> Read and enjoy, with program material none the less.
Adding a center takes away the phantom center, and replaces it with two,
smaller phantom images at half-left and half-right positions. Of course,
with a normal phantom center with two-channel playback, you still have those
half-way images, as well, so a "hard" center does at least allow a center
soloist to remain positioned correctly when listening from well off axis. My
experience with basic two-channel playback, as well as with Dolby-coded
materials, is that even a DPL-style, steered center is an advance over a
phantom, if off-axis listening is involved, although it can also have a
tendency to collapse the image into the center with a lot of program
material.
However, I firmly believe that a hard center is very important, but I am not
so naive that I believe that it will solve all problems. That soundstage is
fake, and going to a hard center will make it better, but it will still be
fake. Enlighten me as to what else a hard center can do, besides solidify the
exact center and help to maintain a centered stage when listening from off
axis.
> >We have to live with that one.
> I disagree. I think we should be moving to (real) multichannel as
> fast as we can run. It's no longer even hard to get multichannel
> delivery with the onset of things like MPEG-AAC, even running at huge
> bit rates for huge safety margins.
Well, I could not agree with you more about the need for more than two
channels, but the five-channel results will still be based upon a fabricated
soundstage and fabricated hall images, with a certain degree of phantom
imaging and phasy manipulations masquerading as real instruments and real
hall reflections. In a small-room environment, the ears will not be fooled
completely, but they will be happier with five channels than with two.
I am sold on the new 5-channel formats in a big way, and have said so in
several Usenet references to the new Delos DVD demo recordings that are now
available. I reviewed one of those in issue 68 of The Sensible Sound, and
reviewed a number of DD, DVD music videos and DTS compact discs in issue 71,
and am convinced that this kind of spatiality control, flawed though it may
be, is the wave of the future, and vastly superior to two-channel audio. My
reviews of the two newer Delos releases will be showing up in a future TSS
issue, but I can say right here that when anyone with a decent DD outfited
system listens to those recordings, they will no longer consider
conventional, two-channel CD sound as state of the art. I still think they
sounded plenty spatious with only one subwoofer working, by the way.
> >I think the masking
> >effects of the multitude of signals above the lower-bass range
> >absolutely negate any subtle effects of stereo low bass.
> What masking effects?
The overwhelming directional and spatiality clues provided by the spaced
satellites, themselves. They utterly obliterate any subtle effects of stereo
bass at very low frequencies for a variety of reasons: much greater loudness
in those clues, the Franssen Effect, and possibly the precidence effect.
> In general, the downward spread of masking is at least -25dB/critical
> band, and more at very low frequencies. Interesting things happen
> when you get well below neural firing rates.
Yes, but here we are talking about masking directional clues and spatiality
effects - which the satellites are providing in such quantity that the
effects you are talking about are just not audible. In addition, we have the
Franssen Effect I mentioned before, and if the sub or subs are further from
the listener than the satellites, we have the precident effect, as well.
Those are wild-card variables that further complicate the easy evaluation of
stereo bass at low-bass frequencies. As I note before, a simple and quick
check is to first position a pair of subs in a stereo location and then move
them to the corner, back off the bass gain a bit to compensate, and then
listen again to see if the spatiality clues are obliterated. (Better yet,
would be to hook up four identical subs in those two set ups and then do a
quick series of A/B comparisons.) With only the subs operating, you might
hear subtle differences, but with the satellites turned back on, the
directional clues provided by them will overwhelm any contributions by stereo
subs.
> That's compared to the upward spread of masking, which runs between
> -15dB/critical band to effectively ZERO db/critical band at high
> levels.
>
> Basically, that first 100Hz is allllll the way at the end of the
> cochlea where it's protected and well-filtered.
Yes, but you are talking about masking monophonic frequencies. I believe that
the downward masking is much more effective when it comes to covering up very
slight directional and spatiality clues provided by stereo subwoofers.
Howard Ferstler
fer...@ibm.net
Gordon Gilbert
Re: 1 or 2 subs?
uO> On 2 Oct 1998 15:01:20 GMT, Howard Ferstler <fer...@ibm.net>
uO> wrote:
uO> Nope, since that will change the frequency response, and would
uO> most likely be audible simply by that.
Sure, that can produce a "differece" result in a blind test, but
we're not looking for frequency response differences, we're looking
for spatial differences. A change in the low frequency response will
probably not have any major effect on whether one can hear stereo bass
spatial clues or not, which is the entire topic of this post.
>>If they are honest with themselves, they will hear no differences,
>>except that the subs in the corner will produce a smoother output,
uO> That would be a difference, wouldn't it? Perhaps better in some
uO> ways, and perhaps a minor compromise.
I have a somewhat interesting setup in that my Carver AL-III
ribbon speakers are pretty much full range all by themselves (they're
flat down to 30Hz), but I also have a Definitive PF-1500 250 watt 15"
subwoofer in the corner. I have the ability (via an external DAC and
6-channel input on my Denon preamp) to compare the same music or movie
source both with and without the subwoofer at the push of a button.
I've recently spent considerable time realigning the settings on
my subwoofer in regard to the main speakers. My AL-III speakers are
currently bi-amped and I've recently switched the main ribbons to be
powered by a Yamaha M-45 180 watt amp (into 4 ohms) that has input
level controls and moved my Carver TFM-35x (350 watt into 4 ohms) to
woofer duty. With the level controls, I can dial in more bass from
the main speakers below 150Hz if so desired. I've also changed my
subwoofer's low-pass frequency (36dB/octave from 80Hz to 50Hz. The
Denon preamp adds a second LP filter at 80Hz for an even steeper drop
above that frequency.
I've compared the low frequency output of the subwoofer by itself
(woofers on the AL-III turned off) at 50Hz, 80Hz, and 100Hz. I used
pure sine-wave tones on one test disc and the Stereophile Test CD
III's warble tones to measure the data with. I also measured the
AL-III all by itself (10" woofers) both near-field and at the
listening position with the same tests and both the subwoofer and
AL-III in combination at 50Hz and 80Hz using the same tests again.
I mention the near-field measurements for Paul Siu's benefit
since he has claimed to me in the past that the Carver bass is "out of
control." For his information, the bass measured flat within +/- 3dB
using these tests on frequencies from 30Hz-100Hz measured 6" from the
woofer. I'd hardly call that out of control Paul. Of course, these
tests aren't as precise as others since I can only sample certain
frequencies or average warble tones. Below 30Hz, the bass rolled off
very quickly.
Anyways, the bass measured significantly worse at the listening
position, as would be expected taking room effects into account. 30Hz
was actually still flat with a large portion of the spectrum, but
there was a significant peak at 40Hz and a dip at 50Hz and lesser peak
at 60Hz (with the pure tone tests). Above that, it was fairly flat
again. Using the Definitive subwoofer at the same levels, I got
similar results (although response was flat at 25Hz and almost flat at
20Hz), although the dips and peaks at 50Hz and 60Hz weren't as bad,
which does seem to indicate to me that corner placement of a subwoofer
can offer smoother response than spaced stereo woofers.
Interestingly, however, I got the best results when I combined
the AL-III and Definitive sub together with the Sub set at 50Hz and
the sub's phase setting set at 180 degrees. At zero degrees, the
peaks and dips were even *worse* than either by itself. At 180
degrees, however, the entire bass spectrum measured pretty flat with
an approximately +/- 3.5dB variation from 20Hz-125Hz. This indicates to
me that a second sub placed somewhere *other* than the same corner
might be able to smooth response out more than a single sub alone. I
note that this jives with some recommendations of using two subs with
one in the corner and another placed elsewhere to smooth out peaks. I
don't believe a second sub belongs in the opposite corner.
So much for frequency response information. I mentioned that I
could compare stereo bass from the AL-III (flat at 30Hz) to that with
a subwoofer set at either 50Hz or 80Hz. I've done this numerous times
with many music discs and I've found more often than not that the
AL-III sounds virtually identical to the response with the subwoofer
on. I have found some exceptions, but the differences seemed to be
frequency in nature and could be explained by the elimination of the
peaks and dips of the AL-III by itself. I was surprised to discover
just how low the AL-III can go by itself. I think with most musical
material, you don't need a sub with the AL-III for extension. It's
nice how in my room it gets smoothed out using one though. Of course,
pipe organ music and other material with bass below 30Hz does get a
nice boost and it also works well for the LFE channel on Dolby Digital
and DTS material. I was using only a sub in the past, but upon buying
a 2nd amplifier, I've been using the AL-IIIs in a bi-amp configuration
with the sub.
uO> Even then, I can't think why not, so long as you're not sitting
uO> 20 feet away.
uO> So you claim, and others claim differently. I wouldn't call a
uO> mono subwoofer havoc, but it is a practical compromise that
uO> usually obtains significant benefits at the cost of ultimate
uO> reproduction. If you've tried stereo subs and you didn't like
uO> it, don't use them.
I personally have yet to encounter this "space" enhancement by
using only my AL-III's in stereo bass compared with just using the
subwoofer. In the past I did A/B comparisons of the sub crossed at
100Hz straight to the ribbons and using the AL-III full range by
itself and found myself hard pressed to tell any major differences in
the bass in either of this configurations. Using them together,
however, seems to provide the best response in my room.
>>I have listened to mono subs with the crossover set to about 150 Hz,
>>and it was possible to clearly localize the subwoofer and the
uO> So you're saying that a very audible problem simply disappears in
uO> 1/2 of an octave. Wow. I could buy that with harmonic
150Hz is much easier to localize than 100Hz. I think it's just
that simple. If you have a 36dB/octave crossover and you set your sub
to 75Hz, it's down 36dB at 150Hz and clearly out of the way. Even if
you set it to 100Hz, it's still down 18dB at 150Hz, which is *very*
significant. 1/3 an octave can and does make a dramatic difference in
subwoofers when it comes to being able to localize them. This is why
subs with less steep LP crossovers don't work very well set at 100Hz
and generally need to be set down at 60Hz or 80Hz (possibly lower) to
sound good. Subs need to get "out of the way" in a hurry above 100Hz,
else their output location becomes detectable.
>>The only advantage
>>to dual subs is increased output,
uO> So you say and believe, though others may not. It is possible, I
uO> guess, that those who think that stereo bass can exist, and can
uO> be perceived, are just gearheads clinging to a placebo, though
I'm still to be convinced that stereo bass is a reason to have 2
subs, but I do think for *some* rooms, a 2nd sub *might* offer
smoother response if you play around with its location long enough.
For other rooms, one in the corner is probably the best bet.
uO> the word of a scientist who studies audible perception without an
uO> agenda does kind of tilt my inclination to believe that the
uO> possible benefits of stereo subs aren't just another of my
uO> hallucinations.
I, for one, have yet to hear this benefit. Unless this sense of
"space" thing only applies below 30Hz, I should be able to hear it
using my AL-III speakers alone since they are pretty much flat down to
30Hz. In fact, turning on my sub in that same setup should mess up
the balance since stronger response below 50Hz will then be coming
from one side of the room only. So, I would think the thing to do at
this time would be to ask such individuals that claim this sense of
"space" benefit to provide examples of real world music that contain
this sense of "space" so that I may compare for myself and see if I
can hear this claimed phenominon or not. So, please JJ and others,
what material should I listen to in order to hear this phenominon?
uh OH!
wrote:
>In article <6v8fuh$nc7$1...@agate.berkeley.edu>,
> co...@bouji.cnchost.com wrote:
>Well, I think a lot of high enders are less than honest with themselves.
>Delusion tends to drive the industry.
Oh, I certainly agree with you there, but to universally label the
entire group as bunk throws out morsels of value as well as the rotten
meatloaf. I certainly understand the temptation. As someone who
vainly considers themself a fairly intelligent person, I still feel
somewhat embarassed for having believed much of what the audio cable
industry has belched out as scientific reasoning behind the effects of
cables. It was only after a volley of explanations where I received a
good technical thrashing by some of the more educated members of this
little community, including your friend and mine, Dick Pierce, to whom
I defensively reacted with smart ass remarks, that I began to realize
that while cable effects might be audible, there wasn't a whole lot to
it. It plagues me whenever I see some fancy interconnects
overpackaged with promises of "unveiled highs" and "greater
resolution." Radio Shack interconnects can give you 99% of all that,
and the rest is debateable. Sure, a lot of cables smooth out the
sound, but it usually involves rolling off the higher range, or
providing "filter networks" that provide a crutch for crappy amps as
well. Maybe I'm just a bitter little kid who's ashamed at being
taken, but now I'm quite happy using 14-4, doubled up, as a speaker
wire, with pretty good results. I'm going to try a more extravagant
setup later, with 36 pairs of 24 gage category 5 network cable.
Anybody know the voltage rating of that stuff?
>In the bass range, I was under the assumption that all speakers were
>omnidirectional, except for dipoles. Do we hear that phase shift?
Do you hear the effects of delay from the reflected sound? Certainly,
it adds a sense of depth in the upper range. It would indicate that
it might add to the experience of room size, but honestly, I don't
know.
>> >Yeah, if we wanted to have an out-of-phase, effect on a recording,
>> >with "spacious" bass, we could do the low bass out of phase, but
>> >doing so would detract from the overall low-bass levels,
>> He's talking about delays of a few milliseconds between channels, not
>> opposite polarity.
>Is this audible at frequencies below 80 Hz?
He says so, and that's what he studies. It's my opinion. Can I prove
it? I have neither the time, inclination, or resources for a proper
scientific study. Well, if somebody wants to give me a grant so that
I can live a month or two without working, rent a good listening room,
make some suitable recordings and pay JJ and/or Dick to set up the
facility and supervise the recordings for the greatest sensitivity,
I'm all for it. Any takers?
>> As I recall, they only phase shift the surround encoding by about 90
>> degrees, so that there is no cancellation occuring when put to mono,
>> but rather a failure to constructively interfere.
>Identical signals are shifted plus 90 degrees in one channel and minus 90
>degrees in the other, for a total difference of 180 degrees. The steering
>supposedly ignores all other phase differences, but I suppose the quality of
>differentiation will vary. The steering is supposed to ignore simple
>difference signals that would be routed with a simple L-R, Hafler-like
>circuit. There is complete cancellation of the surround channels with mono
>playback.
Well, if you're right, I learned something. thanks.
>There is no doubt that those phase shifts, other than possibly reducing
>output a bit, would not be audible with a mono sub. The question is: if they
>are there below 80 Hz, would reproducing them over a pair of woofers make
>them audible, particularly when we take into consideration all the masking
>effects of frequencies above the bass range?
Yes, that's exactly the question.
> Also, with dual subs we have
>the suckout cancellations that I mentioned previously (related to the Allison
>Effect). It is possible that what some people hear with dual subs is related
>to the cancellation nulls that two subs will generate when playing identical
>signals.
I have no doubt that the cancellation you're referring to some people
find desireable and a false indication of clean bass, leaving little
rumble except for the occasional earthquake when material arrives
below the cancellation area. I hope that I haven't, during this
discussion, implied that your points, for the most part, aren't valid.
The compromises of dual stereo subs are substantial.
>> >Well, the only way to prove it is to do some tests. Try double subs,
>> >first in locations that are close to the main speakers, and then
>> >double them up in the corner. Make sure that the three wild cards
>> >noted above do not intrude and skew your perceptions.
>> Not valid, as they will inevitably change the room response. He'd
>> have to monofy the bass via DSP, and run the same speaker array, and
>> compare the two. Given that he's run FIR filter tests, I think he's
>> been there, done that. I could always be wrong, though.
>Well, the corner would reinforce at certain frequencies, as would the
>proximity of the subs when that close to each other, but once the levels were
>re-adjusted, we could still at least listen for the stereo effects. I think
>you are making the comparison more complex than it needs to be.
Only as complex as it needs to be, and as simple as it can. You could
do what you say, except that you bring into variables frequency
response, not just level. If you could equalize with very high
resolution via something like an NAD RCS 2.2 or one of the other
digital EQ's, you might have a shot at it, although there's also the
issue of the time domain with different room mode excitation which
confuses the direction/phase relationship that you're trying to test.
Keep the experiment simple. Same speaker array, same room, same
locations. The only difference should be whether it's summed mono or
left stereo. If _you_ have the time, and are willing to look into
serious research procedures, I'm sure that you could write a pretty
good article on it, although I'd suggest collaborating with JJ if he's
willing, as any valid test will try to legitimately detect any real
perception, and since he and perhaps Dick seem to have the most
specific knowledge on the subject, might be most helpful in designing
the experiment.
uh OH!
wrote:
>I honestly find it hard to believe that phase shifts in the
>millisecond range will be audible with stereo program material, given
>the overwhelming masking effects of the stereo frequencies above the
>low-bass range.
How about just time delays in the range of 5-10 milliseconds? It only
takes around 40 milliseconds before you can actually hear discrete
echoes.
>The problem is not the recordings or the engineers, per se. It
>involves the limintations of two-channel audio - or any audio system
>that depends on a few channels up front to deliver spatial clues for
>any kind of ensemble performing out front.
While stereo certainly is limited, I vehemently deny that recordings
or engineers are not a significant problem. I read an article where
they interviewed a bunch of Grammy winning engineers about their
favorite monitors. One said B&W 801's and Martin logan something or
others. The rest said Yamaha NS-10's. As useful as NS-10's may be
for evaluation of the lowest common denominator, that's FXXXed.
uh OH!
wrote:
>> >If a person listens to two full-range speakers and uses what they
>> >hear coming from them to determine that "stereo" effects exist in the
>> >low bass, then they are going about it all wrong. They should set up
>> >two subwoofers, crossing over at below 100 Hz (or better yet, at the
>> >more typical 80 Hz), under two satellites, and then listen to a
>> >number of stereo recordings. Then, they should move both of the subs
>> >to a corner off to the sides and listen again.
>> Nope, since that will change the frequency response, and would most
>> likely be audible simply by that.
>Well, it would change the FR, but I think that if you adjust the balance
>properly (with the level controls on the subs, or on the processor, it does
>not matter)
sometimes there might be narrow peaks and dips of greater magnitude
than your average 1/3 octave spectrum analyzer would admit.
> you will at least have response that was as smooth as before
but different.
>That might make things a bit more difficult, but if stereo bass is as strong
>a factor as some people say, we should be able to detect it, even if corner
>placement of the two subs improves smoothness, which it most likely will do.
That would cause false indications of disproving the null hypothesis,
that there is no difference. You'd be putting differences in that
could very well be perceived even if the bass was mono under both test
conditions.
>What we are looking for is proof not only that a mono sub in a corner is not
>going to screw up the stereo effect and spaciousness, but that it will make
>the overall sound better.
That's what you're trying to prove. You've got to forget that as a
prospective experimentor. First, you want to find out what is before
you decide what you're going to claim, I hope. Get it nailed whether
or not mono bass is audibly different than stereo bass, and then find
out about the perception of dual spread subs versus a single location
to the side.
> So, if we follow the guidelines I outlined, we will
>be able to not only determine if a loss in stereo low bass is a non problem,
>but will also be able to determine (after the levels are adjusted) if a
>corner-located bass source is just plain better sounding.
Well, you could certainly find out the latter as a statistical
percentage of how many people prefer what, but preference is not
necessarily more accurate. Remember, a lot of people consider the
cancellation you describe as desireable, whether they know it or not.
I don't think that anyone argues that a subwoofer in a corner versus
two to the sides will probably sound different.
> Part of this will
>result, I believe, in the elimination of the cancellation suckout that should
>always happen when spaced woofer systems, particularly if those spaced
>woofers are not in corners, are in operation.
It may, and you've stated good reasons why, but that irrelevent to the
discussion at hand. This has strayed to 1 or 2 subs and become "Is
Stereo Bass Audibly different than mono bass."
>Yes, and it will prove that a corner-position subwoofer will result in better
>sound than spaced dual subs or spaced full-range speakers.
It will only prove that under those test conditions, if it does prove
so, a corner location yielded a flatter response and higher SPL at the
same output levels. Better sound is subjective, regardless of
perception. The guy in the car with subwoofer ports tuned to 60 Hz
thinks his system kicks ass. I think it's an abomination. To him, it
does sound better than my home system.
>I am not sure what this means. Speakers spaced that far apart will be
>coupling coherently below a certain frequency. They will be cancelling and
>creating a null at a different one. A mono sub eliminates such artifacts.
You're talking about summed frequency response. I thought we were
addressing the audibility of inter-channel phase shifts.
>The notch would be only a few dB deep. The problem gets serious when a pair
>of woofers are, say, 12-feet apart, along a wall or out in front of it, and
>each woofer center is also 6 feet (a distance equal to half that between the
>woofers), or so, from either a side wall or the front wall. This would double
>up the cancellation artifacts.
Then it's a good situation to avoid, isn't it?
> With very wide-spaced subs, or dual subs in
>two corners, the effect would be rather minimal, I think. Note that I use
>two subs, myself, located in corners 22 feet apart, along the front wall of
>my big listening room, but have one dealing only with the center-channel bass
>and the other dealing with everything else, including LFE on Dolby Digital.
>Thus, they really do not deal simultanerously with equal-strength, mono-bass
>signals.
Sounds fun.
>Well, we differ dramatically, here. I do not consider it a compromise at all.
>I consider two full-range speakers, without a sub, as the compromise.
Arny said it best. A speaker without compromise is an oxymoron. Or
maybe he was quoting somebody. I can't remember.
> Also,
>stereo subs are not going to be a disaster, but a big mono unit will work a
>little bit better in terms of smoothing out the low bass, and will see to it
>that no suckout notches can form.
We hope anyway. I've had a single sub in a corner (different abode)
that gave me horrible results. Bass everywhere except in the middle
of the room. Crap fell off the shelves, and it sounded like I didn't
even have decent mid-bass drivers getting down there.
>Correct. Obviously, it will be difficult whether stereo low bass really
>exists in significant enough amounts to matter.
With a good testing facility and DSP power, it wouldn't have to be.
>> >Yes, some spaced-microphone recordings with really wide microphone
>> >placement (certain Telarc recordings, and possibly recordings made
>> >with the Decca Tree) might have a bit of stereo bass at 60-80 Hz,
>> and why not at 40 Hz?
>The spacing is not wide enough.
I've seen microphones placed 20 feet apart. 40 Hz waves are roughly,
what, 27 feet long. A wave originating 30 degrees from either side
would induce about a 10 msec delay, ten feet shifted, which is about
130 degrees difference. Say ten feet apart, that's still 65 degrees
of shift.
>You need to watch what happens when you switch from the small to the large
>mode with the center. With the large mode, the bass is routed nearly
>entirely to the center. With the small mode, it is split and sent to the
>mains, but at lower frequencies they couple coherently, and the low-bass
>levels are higher than with the center-large mode.
My point is that it affects frequencies that are very easy to
differentiate in terms of localization, so make the test invalid, as
it would detect false differences.
>Well, the implication is that most subwoofer companies build mono subs, and
>because they want satisfied customers they would not be about to produce
>designs that were detrimental to high fidelity sound reproduction.
Wait a minute. This is still audio.
> Yes, some
>make the option for dual subs, but that usually involves a need for more
>output power, not stereo low bass.
I'm not trying to guess their motives, but it would be detrimental to
the subwoofer/satellite manufacturer to imply that a single subwoofer
isn't entirely adequate, since the majority of their business will be
just that.
>I would think that customer satisfaction would lead them to produce the best
>products possible, particularly when you get into top models like those
>produced by Paradigm, Hsu, and Velodyne. Their flagship systems are all
>mono.
And they seem to be fine products. Then again, some flagship systems
with very impressive performance aren't.
>> >The only advantage
>> >to dual subs is increased output,
>The big
>problem, ironically, involves spaced full-range speakers, which really can
>exhibit suckout notches in the bass range, if their distances to room
>boundaries is half that of the distance between them.
That's probably why full-range speakers, even though with response
well into the 20's, usually benefit from (a) seperate sub/subs.
Tom Pohorsky
Gordon Gilbert <g...@sssnet.com> wrote:
> I mention the near-field measurements for Paul Siu's benefit
>since he has claimed to me in the past that the Carver bass is "out of
>control." For his information, the bass measured flat within +/- 3dB
>using these tests on frequencies from 30Hz-100Hz measured 6" from the
>woofer. I'd hardly call that out of control Paul. Of course, these
>tests aren't as precise as others since I can only sample certain
>frequencies or average warble tones. Below 30Hz, the bass rolled off
>very quickly.
Given Carver's history of substituting distortion for bass
fundamentals, I think measuring total amplitude from a test tone does
not necessarily measure control.
Just a potshot from the peanut gallery,
Tom.
--
- Tom Pohorsky tomp at Legato dot com
jj, curmudgeon and tiring philalethist
HOWARD W FERSTLER <hfer...@mailer.fsu.edu> wrote:
>that a very-low-bass phase shift in that category will be audible,
>and will have an impact on the depth, imaging, localization,
>soundstaging, and spaciousness of a recording.
I simply point out that there ARE effects from having 2-channel
sub-woofers that aid in the stereo illusion.
With high-frequency components or not. If there are high-frequency
components, you can aid the stereo illusion by getting the attack
times right all the way across the basilar membrane. If there
aren't, you can still get a sense of space that you almost don't even
realize comes from "low frequencies".
>However, I believe
>that while stereo low bass might have audible effects if it were
>listened to alone, when all the other materials on a recording, above
>the low-bass range, add their multitide of stereo effects, the stereo
>impact of low bass phase shift on the sense of spaciousness and
>stereophony is pretty much swamped.
And, I point out that there is NOT much, if any "masking" of low
frequencies by higher frequencies.
You have previously argued that the low frequencies were masked. To
that I simply ask; What's your evidence.
>The bottom line is that I have never heard the effect with musical or
>home-theater program material.
I'm sure you haven't heard it with home-theatre material, it's monoed
on purpose for the .1 channel. I'm also not surprised you haven't
heard it on most musical material. Now try a recording, if you can
find one, that preserves proper interaural time differences.
jj, curmudgeon and tiring philalethist
Howard Ferstler <fers...@yahoo.com> wrote:
>Effects that most admit are just barely audible when listening to
>subwoofers alone will somehow remain audible when the outputs of the
>satellites, which have spatiality and directional effects that are clearly
>and much more immediately audible, are factored in. OK, if you say so.
More specifically, they aren't "just barely audible" and one thing that
attracts people's attention is when they are in CONFLICT with the
rest of the information at other frequencies.
>However, we also have to take into consideration the Franssen Effect, which
>localizes images at the satellites,
Which "fransssen effect". Seriously, what happens when the cues
conflict?
>and the precidence effect, which will
>play a part if the subwoofer or subwoofers happen to be further from the
>listener than the satellites.
Howard, you're leaving out the frequency difference!
>Adding a center takes away the phantom center, and replaces it with two,
>smaller phantom images at half-left and half-right positions.
Actually, it does more than that. Try looking at the perspective you
get as you move back and forth in front of the speaker setup.
>In a small-room environment, the ears will not be fooled
>completely, but they will be happier with five channels than with two.
Why are you so insistant on "fabricated"? Come visit, please, and
you can hear some non-fabrications.
>Yes, but you are talking about masking monophonic frequencies.
And? What is a "monophonic frequency"? A frequency is a frequency,
and is whatever gets to the ear in question.
>I believe that
>the downward masking is much more effective when it comes to covering up very
>slight directional and spatiality clues provided by stereo subwoofers.
There is very little "downward masking".
When other cues completely swamp this, you get a higher level kind of
"masking" perhaps, but when cues contradict, this very often breaks
down. Check out "BMLD" in Moore for a simple but very important
example.