.wav file for "JJ dumps on Clerkie" test
Dr. B. J. Feng
I've been away "doing the work" so I'm really late to this
thread. Saw Arnyk's post about generating the signal.
Arny -- it's NOT a fixed offset but a phase modulation
that JJ is talking about.
I've generated a 10 second .wav file that shows the
localization effect of a 2hz phase modulation
(I think it was 0.1 radian peak modulation). If anyone
wants it, I can email it out. Best if I can email it
to someone who has a >28.8k connection for further distribution
(that's all I can get thru my local telco).
Dave, etal. With all due respect, there are a few
points you guys are ignoring:
1) In the "real" venue one can have wave propagation at low frequencies.
Hence, "stereo" bass does indeed exist in a real life music performance.
This is true for classical, jazz, and pop performances.
>> Howard is wrong <<
2) There is excellent scientific/empirical evidence that low frequency signals
can contribute to spatial localization and spatial sensation (JJ already
pointed everyone to the BMLD work, go read some of it).
>> Howard disbelief stems from his usual lack of knowledge <<
(these two points are enough to call into question the idea of using 1 subwoofer
and mono bass if the goal is the most lifelike recreation of the concert experience).
3) Point 2 is easily proven via the test JJ suggested
>> Howard prefers to keep his head in the sand when his beliefs are put to the test <<
4) Point 1 is easily proven by anyone who's done a few live recordings and then
examined the recorded signal (OLD OLD work, Howard).
>> Howard knows much less about live and recorded music than he realizes <<
The only remaining point of interest to rao (exclusive of whether Howard possesses
the ability to think logically) is whether or not a full bandwidth multi-channel
recording, appropriately reproduced using full range spkrs, can provide additional,
perceivable spatial sensations than cannot be reproduced by the same recording when
reproduced over a 5.1 (single, mono-subwoofer) system.
Howard cannot logically speak to this because:
1) He has an incredibly strong bias against the hypothesis
2) He has not the means or material to test the hypothesis
3) He conveniently ignores (1) and (2) to arrive at his conclusions.
With Kind Regards,
John Feng
Steve Zipser
Nice post, John - and having recorded over a hundred performances live, I
agree point for point.
Zip
In article <39B67913...@attglobal.net>, bf...@attglobal.net says...
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Autumn in New York means chestnuts, fallin leaves, & YANKEE BASEBALL
Howard Ferstler
> >> Howard prefers to keep his head in the sand when his beliefs are put to the test <<
>
> 4) Point 1 is easily proven by anyone who's done a few live recordings and then
> examined the recorded signal (OLD OLD work, Howard).
I prefer to compare commercial recordings that people have
available to buy, rather than make themselves. Indeed, that
is what the vast, vast majority of people have to deal with,
John. Doing comparisons with a mono sub, vs some full-range
speakers with bass that was equal down to about 30 Hz, I
heard no differences with a variety of readily available
recordings. I rather doubt that most people would be able to
hear the difference with recordings they purchase in stores,
played back on good systems in normally good home-listening
environments.
Note also that stereo bass transducers introduce
cancellation artifacts that a mono sub, placed in a corner,
will not produce. So, when comparing the frequency response
input to the room of the mono and stereo transducers will be
different. That might account for the differences some
people think they hear. In addition, a pair of subs will
combine outputs coherently at some frequency (depending on
the spacing) and so their subjective outputs at frequencies
below that frequency will be higher. This might also account
for the heightened sense of bass space.
Well, you know all this already. However, the question is:
have you allowed for its impact in the everyday world of
regular audio buffs?
> >> Howard knows much less about live and recorded music than he realizes <<
> The only remaining point of interest to rao (exclusive of whether Howard possesses
> the ability to think logically) is whether or not a full bandwidth multi-channel
> recording, appropriately reproduced using full range spkrs, can provide additional,
> perceivable spatial sensations than cannot be reproduced by the same recording when
> reproduced over a 5.1 (single, mono-subwoofer) system.
The question for me is whether the other variables I noted
will have an impact when doing A/B comparisons of stereo vs
mono low-bass systems, and also whether this all matters
with the recordings people have available to purchase (as
opposed to those they make themselves for special testing
purposes, or proving hard-to-prove points that cover
borderline inaudible nuances). How well do specialized
tests, in specialized environments, measure what people have
to deal with on a practical, everyday level?
> Howard cannot logically speak to this because:
> 1) He has an incredibly strong bias against the hypothesis
He knows what he has heard with commercially made
recordings, which you guys seem to ignore in favor of
special test signals or special recordings that are set up
to prove your points.
> 2) He has not the means or material to test the hypothesis
He has the ability to compare using commercially available
recordings. Not exactly rocket science.
> 3) He conveniently ignores (1) and (2) to arrive at his conclusions.
And you guys ignore what people have available to purchase
out on the market.
> With Kind Regards,
And kind regards to you, too, John.
Howard Ferstler
Howard Ferstler
>
> Nice post, John - and having recorded over a hundred performances live, I
> agree point for point.
> Zip
Always willing to suck up when and where it will work for
you, right Zip?
Howard Ferstler
George M. Middius
> Always willing to suck up when and where it will work for
> you, right Zip?
Fang isn't that bad, Howie. What's wrong with agreeing with him on
some things? He's a little anal about measurements, but that stuff
is how he makes a living, so it's understandable.
You realize, don't you, that the only support you get on RAO is
from the likes of dickie/Debbie, the lying thieving con artist, and
kooky joey daffy, the vicious, rabid cripple from Seattle? Most of
us react to your disgusting hypocrisy and sheer snottiness, but
Fang is one to put aside emotion and denigrate you for your
ignorance and poseurship. It may be a bitter pill to swallow, but
some RAOers don't have an axe to grind, and actually prefer to talk
about engineering stuff. You have your agenda, and I have mine, but
Fang disdains the sandbox behavior. Which is why he thinks as
little of you as he does of me, I suspect.
George M. Middius
Steve Zipser
Zip
"Howard Ferstler" <hfer...@mailer.fsu.edu> wrote in message
news:39B68331...@mailer.fsu.edu...
Steve Zipser
"Howard Ferstler" <hfer...@mailer.fsu.edu> wrote
> I prefer to compare commercial recordings that people have
> available to buy, rather than make themselves.
Fester, you idiot, there is ultimately no difference - a recording is a
recording - and some of the ones I made or assisted on are commercially
available.
> Indeed, that is what the vast, vast majority of people have to deal with,
John.
Duh! The point about people who make the recordings, Fester (and this is so
obvious that only a moron like you doesn't get it) is that they KNOW WHAT IT
WAS SUPPOSED TO SOUND LIKE.
> Doing comparisons with a mono sub, vs some full-range
> speakers with bass that was equal down to about 30 Hz, I
> heard no differences with a variety of readily available
> recordings.
Then you are deaf, as well as stupid and obtuse.
> I rather doubt that most people would be able to
> hear the difference with recordings they purchase in stores,
Well, you are wrong again, Clerkie.
> played back on good systems in normally good home-listening environments.
Guess that leaves you out!
> Note also that stereo bass transducers introduce
> cancellation artifacts that a mono sub, placed in a corner,
> will not produce.
Oh, here we go again. SUMMING BASS CHANNELS introduces MORE cancellation as
well as fucking up phase, you dummy.
> So, when comparing the frequency response
> input to the room of the mono and stereo transducers will be
> different.
DUH!
> That might account for the differences some
> people think they hear.
You are hopelessly stupid and thickheaded. I think you had a lobotomy, not
a prostate operation.
> In addition, a pair of subs will
> combine outputs coherently at some frequency (depending on
> the spacing) and so their subjective outputs at frequencies
> below that frequency will be higher. This might also account
> for the heightened sense of bass space.
It has nothing to do with it, Dummy.
> Well, you know all this already. However, the question is:
> have you allowed for its impact in the everyday world of
> regular audio buffs?
Wow, you are one BUFF dude, fester!
Zip
Arny Krueger
"Dr. B. J. Feng" <bf...@attglobal.net> wrote in message
news:39B67913...@attglobal.net...
> Dear RAO Freaks,
>
> I've been away "doing the work" so I'm really late to this
> thread. Saw Arnyk's post about generating the signal.
> Arny -- it's NOT a fixed offset but a phase modulation
> that JJ is talking about.
If I had a better descritpion of what the effect is, I could proably
do a better job of demonstrating it.
Personally, I found it illuminating and instructive that phase
differences like that are so audible, even when steady-state.
> I've generated a 10 second .wav file that shows the
> localization effect of a 2hz phase modulation
> (I think it was 0.1 radian peak modulation). If anyone
> wants it, I can email it out.
Please do so. I'd be happy to augment the page.
>Best if I can email it
> to someone who has a >28.8k connection for further distribution
> (that's all I can get thru my local telco).
Cable modem here...
> Dave, etal. With all due respect, there are a few
> points you guys are ignoring:
> 1) In the "real" venue one can have wave propagation at low
frequencies.
> Hence, "stereo" bass does indeed exist in a real life music
performance.
> This is true for classical, jazz, and pop performances.
That seems obvious to me.
> >> Howard is wrong <<
The trick is convincing Howard! ;-)
> 2) There is excellent scientific/empirical evidence that low
frequency signals
> can contribute to spatial localization and spatial sensation (JJ
already
> pointed everyone to the BMLD work, go read some of it).
I missed that pointer. Care to repeat it?
> >> Howard disbelief stems from his usual lack of knowledge <<
The trick is educating Howard! ;-)
> (these two points are enough to call into question the idea of
using 1 subwoofer
> and mono bass if the goal is the most lifelike recreation of the
concert experience).
I think the audibilty of steady-state phase differences with isolated
headphones makes that point, tied with the obvious fact that much
music includes 2 or more uncorrelated low frequency sources.
> 3) Point 2 is easily proven via the test JJ suggested
> >> Howard prefers to keep his head in the sand when his beliefs
are put to the test <<
Wanna take a bet on how much time he's spent with any of the tests at
www.pcabx.com?
> 4) Point 1 is easily proven by anyone who's done a few live
recordings and then
> examined the recorded signal (OLD OLD work, Howard).
Out-of-phase bass in recordings has been a major issue for LPs going
back to the advent of bass response...
> >> Howard knows much less about live and recorded music than he
realizes <<
What did Roy A. have to say about it? ;-)
> The only remaining point of interest to rao (exclusive of whether
Howard possesses
> the ability to think logically) is whether or not a full bandwidth
multi-channel
> recording, appropriately reproduced using full range spkrs, can
provide additional,
> perceivable spatial sensations than cannot be reproduced by the
same recording when
> reproduced over a 5.1 (single, mono-subwoofer) system.
Obviously, it can't.
> Howard cannot logically speak to this because:
> 1) He has an incredibly strong bias against the hypothesis
Very clearly so.
> 2) He has not the means or material to test the hypothesis
I think we've shown that the means and material can be delivered on a
silver platter...
> 3) He conveniently ignores (1) and (2) to arrive at his
conclusions.
I think the conclusion was reached some time ago and has remained
static.
Howard Ferstler
>
> You are the expert on sucking, Fester - up down all around.
Well, gee, Zip, many people here would say that I alienate
nearly everybody on the newsgroups. Is that some kind of
special sucking up that only you would be familiar with?
Howard Ferstler
Howard Ferstler
>
> "Howard Ferstler" <hfer...@mailer.fsu.edu> wrote
> > Note also that stereo bass transducers introduce
> > cancellation artifacts that a mono sub, placed in a corner,
> > will not produce.
>
> Oh, here we go again. SUMMING BASS CHANNELS introduces MORE cancellation as
> well as fucking up phase, you dummy.
The kind of canceling I am referring to is acoustic in
nature and exists out in the listening room. It has nothing
to do with phase artifacts within the program material
itself.
> > So, when comparing the frequency response
> > input to the room of the mono and stereo transducers will be
> > different.
> DUH!
Different in terms of frequency response.
> > That might account for the differences some
> > people think they hear.
> You are hopelessly stupid and thickheaded. I think you had a lobotomy, not
> a prostate operation.
Thank you for this audio-related comment.
> > In addition, a pair of subs will
> > combine outputs coherently at some frequency (depending on
> > the spacing) and so their subjective outputs at frequencies
> > below that frequency will be higher. This might also account
> > for the heightened sense of bass space.
> It has nothing to do with it, Dummy.
It has lots to do with it, because that means that down low
the dual subs will be louder, even though their outputs
match that of the mono sub at slightly higher bass
frequencies. They do not add coherently at those, but they
do at lower frequencies. The changeover point will depend
upon how far apart they are. So, dual subs will ramp the
bass output upward as the frequency drops, compared to an
identical mono sub.
Howard Ferstler
LargeMarge
says...
"George" fastens the chinstraps on his flowerpot as
he prepares for battle:
I know of at least eight (8) RAO-ers
who support Howard. And BTW, since
we are writing Boonlish, I have received
at least eight (8) e-mails supporting me.
Ar Har Har Har!!!
Marge
Gene Lyle
(LargeMarge) wrote:
>
>I know of at least eight (8) RAO-ers
>who support Howard. And BTW, since
>we are writing Boonlish, I have received
>at least eight (8) e-mails supporting me.
>Ar Har Har Har!!!
>
>
>Marge
>
Oh wow, eight! That's gotta be a world record! Man!!
Gene Lyle
Marge
Howard Ferstler
> > >> Howard disbelief stems from his usual lack of knowledge <<
>
> The trick is educating Howard! ;-)
I am not the only person around who feels that a mono sub can do
the job just fine. The people who feel as I do have made use of
commercially available recordings, I believe, rather than test
signals that do not relate to what people can purchase in record
stores.
> > >> Howard prefers to keep his head in the sand when his beliefs
> are put to the test <<
>
> Wanna take a bet on how much time he's spent with any of the tests at
> www.pcabx.com?
Wanna take a bet on how many recordings I have listened to while
switching back and forth between a mono sub and spaced woofer
systems?
> > >> Howard knows much less about live and recorded music than he
> realizes <<
Tell that to the guys who gave my record-review books good
reviews. Say, how many record reviews (books or magazine
versions) have you guys published? I am not trying to demean you,
but in this case you have indicated that I do not know much about
live and recorded music, and yet I am the guy who went to the
trouble to get the record-review books published. All you two do
is blowhard about your tests.
> > The only remaining point of interest to rao (exclusive of whether
> Howard possesses
> > the ability to think logically) is whether or not a full bandwidth
> multi-channel
> > recording, appropriately reproduced using full range spkrs, can
> provide additional,
> > perceivable spatial sensations than cannot be reproduced by the
> same recording when
> > reproduced over a 5.1 (single, mono-subwoofer) system.
> Obviously, it can't.
Well, multiple woofers certainly can produce a lot of
cancellation interactions. And they certainly can reinforce
coherently down really low in unpredictable ways. Yes, they
certainly can sound different. I think you two are
misinterpreting what else you believe they can do.
> > Howard cannot logically speak to this because:
>
> > 1) He has an incredibly strong bias against the hypothesis
> Very clearly so.
I cannot hear what you claim to hear, and I think that you hear
what you claim, because you are using specialized test signals,
rather than commercially produced recordings.
> > 2) He has not the means or material to test the hypothesis
>
> I think we've shown that the means and material can be delivered on a
> silver platter...
Easy. Just get some commercially produced recordings and do some
A/B comparisons. Of course, even then you have to take into
account the suckout interactions of dual subs, compared to a mono
sub, and have to handle the fact that dual subs will add
coherently below a certain frequency, which will enrich the low
bass with extra power. I think that much of what you guys are
hearing relates to those two phenomena.
> > 3) He conveniently ignores (1) and (2) to arrive at his
> conclusions.
> I think the conclusion was reached some time ago and has remained
> static.
Well, the laws of physics are immutable. I will agree with you on
that one. No point in me changing my conclusion about how those
laws relate to what I hear with commercially produced recordings.
Howard Ferstler
Arny Krueger
"Howard Ferstler" <fer...@attglobal.net> wrote in message
news:39B6F6C1...@attglobal.net...
> Arny Krueger wrote:
>
> > > >> Howard disbelief stems from his usual lack of knowledge
<<
> > The trick is educating Howard! ;-)
> I am not the only person around who feels that a mono sub can do
the job just fine.
Howard, people use exactly the same argument for believeing that LPs
are sonically transparent than CDs, and that tubed equipment is
necessarily more sonically transparent than SS, that kilobuck speaker
wires sound better than far less expensive wires that are properly
engineered, etc.
>The people who feel as I do have made use of commercially available
recordings, I believe, rather than test
> signals that do not relate to what people can purchase in record
stores.
Prove that the test signals are irrelevant to anything people buy in
stores.
> > > >> Howard prefers to keep his head in the sand when his
beliefs
> > are put to the test <<
>
> > Wanna take a bet on how much time he's spent with any of the
tests at
> > www.pcabx.com?
> Wanna take a bet on how many recordings I have listened to while
> switching back and forth between a mono sub and spaced woofer
> systems?
Howard, people use exactly the same argument for believeing that LPs
are sonically transparent than CDs, and that tubed equipment is
necessarily more sonically transparent than SS, that kilobuck speaker
wires sound better than far less expensive wires that are properly
engineered, etc.
> > > >> Howard knows much less about live and recorded music than
he realizes <<
> Tell that to the guys who gave my record-review books good
> reviews. Say, how many record reviews (books or magazine
> versions) have you guys published? I am not trying to demean you,
> but in this case you have indicated that I do not know much about
> live and recorded music, and yet I am the guy who went to the
> trouble to get the record-review books published. All you two do
> is blowhard about your tests.
Howard, people use exactly the same argument for believing that LPs
are sonically transparent than CDs, and that tubed equipment is
necessarily more sonically transparent than SS, that kilobuck speaker
wires sound better than far less expensive wires that are properly
engineered, etc.
> > > The only remaining point of interest to rao (exclusive of
whether
> > Howard possesses
> > > the ability to think logically) is whether or not a full
bandwidth
> > multi-channel
> > > recording, appropriately reproduced using full range spkrs, can
> > provide additional,
> > > perceivable spatial sensations than cannot be reproduced by the
> > same recording when
> > > reproduced over a 5.1 (single, mono-subwoofer) system.
> > Obviously, it can't.
> Well, multiple woofers certainly can produce a lot of
> cancellation interactions. And they certainly can reinforce
> coherently down really low in unpredictable ways. Yes, they
> certainly can sound different. I think you two are
> misinterpreting what else you believe they can do.
Howard, the sound field in a concert hall is almost always generated
by multiple sources operating over a wide range of frequencies. This
creates a sound field containing a wide variety of sounds in a wide
variety of frequency ranges that provides each ear differerent
perspectives on the music.
Our sound systems reproduce the differences in the upper bass,
midrange, and treble. Single subwoofer systems don't reproduce the
differences in the lower bass. I've proven to my satisfaction with a
DBT that there is an added audible dimension to bass that strikes the
ears with differing phases even with isolated headphones. With
isolated headphones there is no reinforcement or cancellation in my
listening room because my listening room is not involved.
Its a classic chicken-and-egg situation.
Because LPs can't handle stereo sub-bass very well (they don't handle
mono sub-bass very well, either) the audio industry for over 40 years
has been treating stereo sub-bass like it was the plague. Stereo
sub-bass was intentionally destroyed by recording and mastering
engineers with the blessing of just about everybody. It was thought
to be sonically irrelevant ("Bass is non-directional') and it could
cause big problems for both producers and consumers.
I now know that while bass IS non-directional, directionality is not
the only kind of listening experience that stereo sub-bass conveys.
While http://www.pcabx.com/technical/stereo_bass/index.htm may not
be the best demo in the world (Dr. Feng says he is going to send me
files for a better demo) it shows that stereo sub-bass does create a
different listening experience. If one listens to these files using
isolated headphones, which address the cancellation issues you raise,
one still hears a difference. It's a freakin' DBT, Howard.
Some day Howard you need to realize that a DBT is not like a
benediction that we say to make things "holy audio".
DBTs are a reliable way to figure out if there is an audible
difference. If a really good DBT says that there is no audible
difference, then yes, there may not be an audible difference. But if
the DBT says there is a audible difference, THEN THERE IS A
DIFFERENCE AND WE NEED TO DEAL WITH IT!
> > > Howard cannot logically speak to this because:
> > > 1) He has an incredibly strong bias against the hypothesis
> > Very clearly so.
> I cannot hear what you claim to hear, and I think that you hear
> what you claim, because you are using specialized test signals,
> rather than commercially produced recordings.
Howard, what is going to happen is:
(1) Dr. Feng has promised to email me some test signals that are more
representitive. I'm going to audition them and if they seem useful to
me, up they go at
http://www.pcabx.com/technical/stereo_bass/index.htm .
(2) Someplace along the way we'll find some recordings with stereo
sub-bass that can be posted in excerpts and up they go at
http://www.pcabx.com/technical/stereo_bass/index.htm .
Howard I preduct that just like you've done to date, you won't listen
to them, and you'll prattle on indefinately about what a waste and
snake oil stereo sub-bass is.
>
> > > 2) He has not the means or material to test the hypothesis
> >
> > I think we've shown that the means and material can be delivered
on a
> > silver platter...
> Easy. Just get some commercially produced recordings and do some
> A/B comparisons. Of course, even then you have to take into
> account the suckout interactions of dual subs, compared to a mono
> sub, and have to handle the fact that dual subs will add
> coherently below a certain frequency, which will enrich the low
> bass with extra power.
False claim on many grounds:
(1) Stereo sub-bass is already known, by means of DBTs to be audible
with isolated headphones where they are no suckouts and/or power
level or frequency response issues.
(2) If you have multichannel bass, you obviously don't have the same
signal coming out of both speakers, so the suck-outs you fear won't
happen. It seems obvious to me that one solution to the problem of
mono bass or bass that is centrally imaged is (gasp) the center
channel subwoofer.
>I think that much of what you guys are hearing relates to those two
phenomena.
Since I've been clear about saying that the effect is clear with
isolated headphones, I'm beginning to think that you are not catching
all the relevant details in this debate.
> > > 3) He conveniently ignores (1) and (2) to arrive at his
> > conclusions.
>
> > I think the conclusion was reached some time ago and has remained
> > static.
> Well, the laws of physics are immutable.
They've always said that bass in a room is not mono.
>I will agree with you on that one. No point in me changing my
conclusion about how those
> laws relate to what I hear with commercially produced recordings.
The laws of physics have always said that bass in a room is not mono.
The custom of FORCING the bass on recordings to be mono traces back
to the technical limitations of LP technology. It was based on the
true idea that sub-bass is non-directional, but also on the false
idea that directionality is the only aspect of sub-bass that can be
reliably perceived.
Dr. B. J. Feng
Howard Ferstler wrote:
>
> "Dr. B. J. Feng" wrote:
>
> > >> Howard prefers to keep his head in the sand when his beliefs are put to the test <<
> >
> > 4) Point 1 is easily proven by anyone who's done a few live recordings and then
> > examined the recorded signal (OLD OLD work, Howard).
>
> I prefer to compare commercial recordings that people have
> available to buy, rather than make themselves.
How did JJ put it? Why do you want to lock people in to the oldest
and most antiquated technology? Summed (mono) bass is an artifact
that was necessary in the LP days. The recording medium has improved
(wax cyl => 78 => LP => CD => ?). The recording equipment has improved
(we're doing 16bit at up to 196kHz multi-channel here, and will soon have 24bit capability).
Why not capture more of the sound in the performance venue than we did with LP?
Why stand in the face of progress? Why are you against commercial
recordings that preserve the full bandwidth stereo signal? BTW,
there is multi-channel bass on the master tapes. It only requires a
re-mix to get that onto a CD. There are no technical reasons why all
CD releases should not have stereo bass. There's no reason why all
new releases shouldn't have full bandwidth independent channel information.
(snip)
> Doing comparisons with a mono sub, vs some full-range
> speakers with bass that was equal down to about 30 Hz, I
> heard no differences with a variety of readily available
> recordings.
This is the final question to answer, e.g. what of the practical
value of stereo bass. JJ says he has recordings (commercial) where
it's readily noticable. You say you never hear any difference.
He is a internationally recognized expert on human hearing and
audio. You are an armchair speculator that writes equipment/music
reviews for consumer entertainment magazines. JJ has a wide variety
of state of the art and readily available commercial recordings in
stereo, digital dolby, and >2 channel, and a great lab for doing
solid empirical testing. You have a home system that's been tweeked
to your satisfaction. Who's judgement do you trust in matters of
scientific opinion? Independent bass channels may indeed have no
perceived value for you. You cannot extrapolate that to the
rest of the world.
> Note also that stereo bass transducers introduce
> cancellation artifacts that a mono sub, placed in a corner,
> will not produce. So, when comparing the frequency response
Careful not to let yourself get too caught up in measurement
details. In the end, only the realism of the reproduction
is important, not how well distributed your bass nulls are in
your particular room. Certainly, stereo bass presents real problems for
accurate reproduction. Just as certainly, stereo bass can
excite localization and spatial hearing cues. The former does
not automatically justify ignoring the second.
> > The only remaining point of interest to rao (exclusive of whether Howard possesses
> > the ability to think logically) is whether or not a full bandwidth multi-channel
> > recording, appropriately reproduced using full range spkrs, can provide additional,
> > perceivable spatial sensations than cannot be reproduced by the same recording when
> > reproduced over a 5.1 (single, mono-subwoofer) system.
>
> The question for me is whether the other variables I noted
> will have an impact when doing A/B comparisons of stereo vs
> mono low-bass systems,
Which you are not equiped to investigate given your description of your setup
and hearing ability.
> and also whether this all matters
> with the recordings people have available to purchase
If people took your attitude, all audio electronics would have
less than 50dB of inter-channel separation above 5kHz when LP's
were the primary playback medium. In truth, playback systems
evolved considerably beyond the limitations of the LP (for the most
part), and hence were able to readily take advantage of much of the
increased capability of CD the instant it became available.
To suggest that all systems be limited to the capabilities of
the most widely available current source material is . . .
how do I put it kindly ... well, it's plain stupid.
With Kind Regards (nevertheless)
John Feng
Dr. B. J. Feng
Arny and Tom bring up a good point (as does Howard).
Despite the facts about LF perception, the question
remains (in rao) about the real-world perceivability
and value of full bandwidth multi-channel reproduction.
How many of you have a full bandwidth (okay, flat to 40Hz)
5 channel setup, and have compared it to the same
with a good HP to the 5 in 5.1 using full bandwidth
multi-channel source material (movie sound tracks included)?
John
P.S. BMLD -- start with Yost, Green and McFadden, 1975 JASA.
Brian Moore talks about it in his 90% decent book, An
Introduction to the Psychology of Hearing (Academic Press)
Dr. B. J. Feng
Called sucking up to oneself, e.g. "self-sucking".
Yuck!!
John
Dr. B. J. Feng
Howard's right. He's concerned with reproduction anomalies.
However, even if he had JJ's stunning good looks, it would
not change my opinion of him one bit.
Howard Ferstler wrote:
> Steve Zipser wrote:(snip)
> > Oh, here we go again. SUMMING BASS CHANNELS introduces MORE cancellation as
> > well as fucking up phase, you dummy.
>
> The kind of canceling I am referring to is acoustic in
> nature and exists out in the listening room.
John
Dr. B. J. Feng
Arny Krueger wrote:
> (snip)
>
> I now know that while bass IS non-directional,
Let me try to reword your explanation:
One fact of life is test results are often very much
a product of how the test question is presented (e.g.
the test paradigm).
Bass is non-directional when a steady state signal is played,
regardless of the static phase differences between channels (2, 3, 5 whatever).
Howard's faulty logic is that this test situation is representative
of real world music. In the real world, there are time-varying phase
differences (interaural), and these clearly engender localized/spatial
hearing perception.
"Limiting test paradigm => limiting results => limiting conclusions"
(snip)
> If one listens to these files using (snip)
> one still hears a difference. It's a freakin' DBT, Howard.
I also hear the effect on my stereo speaker system.
(snip)
> (1) Dr. Feng has promised to email me some test signals
Just ask if you want a more extreme phase shift example.
(snip)
> (2) If you have multichannel bass, you obviously don't have the same
> signal coming out of both speakers, so the suck-outs you fear won't
> happen.
I hope Tom will step in to give an opinion. Multiple LF sources will
introduce more bass nulls/peaks in the listening room. With two
LF sources, these will be readily audible 99% of the time.
With full bandwidth multi-channel, however, you have
5 sources of LF bass. This has the effect of reducing the magnitude
of the peak/nulls (unless you are really unlucky in your room/spkr
placement), and also increase the uniformity and density of the
anomalies. The end result should, in most cases, be considerably less
objectionalble than anomalies from using stereo LF bass reproduction.
George M. Middius
> Given that many actively posting, RAO types are borderline lunatics,
We wish you well in your treatment, Clerkie.
George M. Middius
George M. Middius
> You made the accusation,
> > Fang isn't that bad, Howie. (snip) He's a little anal about measurements
> If you mean I'm anal about people making measurements (and interpreting them)
> without full knowledge of the caveats inherent in all known measurements.
> Yes, I am as anal as they come. If you mean I'm anal about the need for
> measurements to judge the quality of a stereo system, please provide proof
> for your baseless accusation
A demand for "proof" from someone who says Arnii F. Krooger is
"a nice guy" -- that's a laugh.
> > but Fang disdains the sandbox behavior.
> Thanks, George, but you forget my occasional dalliance with Greg S, our
> resident philosopher.
Now that is a baseless accusation that demands proof.
George M. Middius
Howard Ferstler
>
>
> Howard's right. He's concerned with reproduction anomalies.
> However, even if he had JJ's stunning good looks, it would
> not change my opinion of him one bit.
Perhaps, for the benefit of the newcomers (as well as for
your friend "Steve,") you would post a summary of that
opinion. Try to be brief.
Howard Ferstler
Arny Krueger
>
>
> Arny Krueger wrote:
> > (snip)
> >
> > I now know that while bass IS non-directional,
>
> Let me try to reword your explanation:
> One fact of life is test results are often very much
> a product of how the test question is presented (e.g.
> the test paradigm).
> Bass is non-directional when a steady state signal is played,
> regardless of the static phase differences between channels (2, 3,
5 whatever).
OK, but if you play two signals with different steady state phase
differences in quick sucession, it still may seem non-directional (it
does to me) but it also sounds "different".
> Howard's faulty logic is that (his) test situation is
representative
> of real world music. In the real world, there are time-varying
phase
> differences (interaural), and these clearly engender
localized/spatial
> hearing perception.
Agreed.
> "Limiting test paradigm => limiting results => limiting
conclusions"
Agreed.
> (snip)
> > If one listens to these files using (snip)
> > one still hears a difference. It's a freakin' DBT, Howard.
> I also hear the effect on my stereo speaker system.
But the difference may relate to the issues that Howard raised.
> (snip)
> > (1) Dr. Feng has promised to email me some test signals
> Just ask if you want a more extreme phase shift example.
> (snip)
Than what? I hope this means you've recently sent me something. ;-)
> > (2) If you have multichannel bass, you obviously don't have the
same
> > signal coming out of both speakers, so the suck-outs you fear
won't
> > happen.
> I hope Tom will step in to give an opinion. Multiple LF sources
will
> introduce more bass nulls/peaks in the listening room. With two
> LF sources, these will be readily audible 99% of the time.
My take is that those bad things only happen undesirably when the LF
sources are playing the same signal. We are doing recreation here,
right? Are there bass nulls/peaks in a performance room when music is
being played? I'm pretty sure they are there & I'm pretty sure that
I've heard them.
> With full bandwidth multi-channel, however, you have
> 5 sources of LF bass.
Only if you play it that way. 5 independent channels for 5 sources of
LF bass right? Do they all have to be playing in phase all of the
time? I think not! Looks to me like we just found 4 more "paint
brushes" for the mixdown crew to "play with".
>This has the effect of reducing the magnitude
> of the peak/nulls (unless you are really unlucky in your room/spkr
> placement), and also increase the uniformity and density of the
> anomalies. The end result should, in most cases, be considerably
less
> objectionalble than anomalies from using stereo LF bass
reproduction.
I think for the reasons, and by means of using some of the techniques
I suggested.
Dr. B. J. Feng
Arny Krueger wrote:
> "Dr. B. J. Feng" <bf...@attglobal.net> wrote in message
> > Arny Krueger wrote:
> > > (snip)
> > > I now know that while bass IS non-directional,
> > Let me try to reword your explanation:
(snip)
> > Bass is non-directional when a steady state signal is played,(snip)
> OK, but if you play two signals with different steady state phase
> differences in quick sucession, it still may seem non-directional (it
> does to me) but it also sounds "different".
The quick sucession is in fact introducing a dynamic aspect to the
signal. An instantaneous phase shift ... the extreme of a phase modulation.
John
P.S. Later on the other points.
George M. Middius
> > However, even if he had JJ's stunning good looks, it would
> > not change my opinion of him one bit.
> Perhaps, for the benefit of the newcomers (as well as for
> your friend "Steve,") you would post a summary of that
> opinion. Try to be brief.
So you need to inflate your ego with periodic bouts of masochistic
punishment. Just like Krooger in that way.
George M. Middius
Arny Krueger
> Dear RAO Freaks,
>
> I've been away "doing the work" so I'm really late to this
> thread. Saw Arnyk's post about generating the signal.
> Arny -- it's NOT a fixed offset but a phase modulation
> that JJ is talking about.
>
> localization effect of a 2hz phase modulation
> (I think it was 0.1 radian peak modulation). If anyone
> to someone who has a >28.8k connection for further distribution
> (that's all I can get thru my local telco).
This file can be downloaded from
http://www.pcabx.com/technical/stereo_bass/index.htm . Its labelled
as "Stereo Bass II (dynamic) - Easy" It is about 1.8 megs. The
reference file is about half that size (mono).
Arny Krueger
Agreed. Just trying to make it easy for listeners. ;-)
I have another (unwritten) motto for www.pcabx.com besides the "snake
oil" thing: "If you come here and don't hear a difference in a DBT,
don't blame me!" ;-)
Now people can have it either way at
http://www.pcabx.com/technical/stereo_bass/index.htm .
Thanks for the sample.
Howard Ferstler
>
> "Howard Ferstler" <fer...@attglobal.net> wrote in message
> news:39B6F6C1...@attglobal.net...
> > I am not the only person around who feels that a mono sub can do
> > the job just fine.
> Howard, people use exactly the same argument for believeing that LPs
> are sonically transparent than CDs, and that tubed equipment is
> necessarily more sonically transparent than SS, that kilobuck speaker
> wires sound better than far less expensive wires that are properly
> engineered, etc.
At the risk of name dropping, Nousaine has written entire
reviews and essays around the concept of single subwoofers,
and he has backed up his findings with some pretty good
research. Perhaps he and the people he has used in his
various comparison sessions were as wrong-headed and tin
eared as you believe that I am.
Also, remember that many manufacturers offer a single sub
output on their processors, and as of the last time I
checked the LFE channel on both the Dolby Digital and DTS
coding systems involved only one channel. Yes, they are not
particularly music oriented and there really is no reason
for a sub with the musical coding itself, but in any case
some people, somewhere, believe that a mono sub can do the
job just fine. What's more, if what you guys say is true,
the LFE explosions in movies would sound a lot better if
there were two LFE channels, or even more. I guess Dolby and
DTS got it wrong.
> >The people who feel as I do have made use of commercially available
> recordings, I believe, rather than test
> > signals that do not relate to what people can purchase in record
> stores.
> Prove that the test signals are irrelevant to anything people buy in
> stores.
Well, I heard no spatially related differences between a
single sub and spaced woofer systems, using commercially
produced recordings. With test-tone inputs, I did measure
differences in terms of low-bass uniformity and cancellation
artifacts, however. Perhaps those are what you guys are
hearing when you do your particular comparisons. Guess what?
They have nothing to do with the spatiality issue.
> > > > >> Howard prefers to keep his head in the sand when his
> beliefs
> > > are put to the test <<
> > > Wanna take a bet on how much time he's spent with any of the
> tests at
> > > www.pcabx.com?
> > Wanna take a bet on how many recordings I have listened to while
> > switching back and forth between a mono sub and spaced woofer
> > systems?
> Howard, people use exactly the same argument for believeing that LPs
> are sonically transparent than CDs, and that tubed equipment is
> necessarily more sonically transparent than SS, that kilobuck speaker
> wires sound better than far less expensive wires that are properly
> engineered, etc.
Gee, Arny. Perhaps you did not read what I said carefully
enough. I said that with commercially produced recordings I
heard no spatiality advantages in the low bass, when
comparing a mono sub (working below 80 Hz) to two full-range
systems (flat to 30 Hz). You make it sound like I was
listening for spiritual artifacts, the way that the crazies
do when they listen to LP records and SET amps. However,
what I was listening for were spatiality differences and I
heard none. The entire enterprise was a waste of time.
> > > > >> Howard knows much less about live and recorded music than
> he realizes <<
> > Tell that to the guys who gave my record-review books good
> > reviews. Say, how many record reviews (books or magazine
> > versions) have you guys published? I am not trying to demean you,
> > but in this case you have indicated that I do not know much about
> > live and recorded music, and yet I am the guy who went to the
> > trouble to get the record-review books published. All you two do
> > is blowhard about your tests.
> Howard, people use exactly the same argument for believing that LPs
> are sonically transparent than CDs, and that tubed equipment is
> necessarily more sonically transparent than SS, that kilobuck speaker
> wires sound better than far less expensive wires that are properly
> engineered, etc.
What kind of argument might that be? I am a record reviewer
and I have compared using commercially produced recordings.
You have used special test signals and maybe custom-made
recordings and then have often compared using headphones.
Well, just how much mono vs stereo bass comparing have you
done using real speakers and subs in real rooms, with
commercially produced recordings? Have you bothered to sort
out any additional variables that would involve the way
multiple woofers would interact, in comparison to a single
sub in a corner?
Nobody has more respect for test signals than I do, but the
last thing I do with them is to twist what I find with such
signals to the extent that I overlay what I heard over what
I believe most people would hear with recordings they
purchase in stores.
> > > > The only remaining point of interest to rao (exclusive of
> whether
> > > Howard possesses
> > > > the ability to think logically) is whether or not a full
> bandwidth
> > > multi-channel
> > > > recording, appropriately reproduced using full range spkrs, can
> > > provide additional,
> > > > perceivable spatial sensations than cannot be reproduced by the
> > > same recording when
> > > > reproduced over a 5.1 (single, mono-subwoofer) system.
> > > Obviously, it can't.
> > Well, multiple woofers certainly can produce a lot of
> > cancellation interactions. And they certainly can reinforce
> > coherently down really low in unpredictable ways. Yes, they
> > certainly can sound different. I think you two are
> > misinterpreting what else you believe they can do.
> Howard, the sound field in a concert hall is almost always generated
> by multiple sources operating over a wide range of frequencies. This
> creates a sound field containing a wide variety of sounds in a wide
> variety of frequency ranges that provides each ear differerent
> perspectives on the music.
Have you validated that (1) this is audible at very low
frequencies, independently from the influence of signals at
higher frequencies and (2) that a similar phenomenon would
be audible in home-listening rooms with commercially
produced recordings?
> Our sound systems reproduce the differences in the upper bass,
> midrange, and treble. Single subwoofer systems don't reproduce the
> differences in the lower bass. I've proven to my satisfaction with a
> DBT that there is an added audible dimension to bass that strikes the
> ears with differing phases even with isolated headphones.
I will not deny that differences might be audible with
headphones. However, in a typical listening room, with
speakers, you have those frequency-response variables to
deal with, not to mention the spatial clues being delivered
at the same time by higher frequencies coming from the
satellites, and those are nearly impossible to sort out when
comparing a single low-bass transducer and a pair of them.
I will also not deny that with special test signals they
might be audible. However, I am dealing with real-world
recordings and I am telling you that a mono sub, if crossed
over low enough (below 90 Hz, actually) will just not have a
problem. The mass of spatiality clues delivered by the
satellites above 90 Hz will just overwhelm any low-bass
spatiality artifacts.
> With
> isolated headphones there is no reinforcement or cancellation in my
> listening room because my listening room is not involved.
So what? Most people do not listen with headphones. They
listen with speakers in typical rooms, and they listen to
commercially produced recordings that have a plethora of
spatiality clues above the low-bass range that smother any
minor spatiality clues delivered by spaced woofer systems.
In addition, spaced woofer systems present problems of their
own that a mono sub, properly located, will not have.
So, in order to correct one very minor problem, you are
willing to put up with a bigger one. Count me out.
> Its a classic chicken-and-egg situation.
>
> Because LPs can't handle stereo sub-bass very well (they don't handle
> mono sub-bass very well, either) the audio industry for over 40 years
> has been treating stereo sub-bass like it was the plague.
Well, if there are any mono complements to the bass signals
at all you are possibly going to have interactions that
certainly are a potential problem. A mono sub, properly
positioned and properly crossed over bypasses those
problems. Now, in order to deliver subtle spatiality clues
down really low, you are going to reintroduce the
woofer-interaction problem.
> Stereo
> sub-bass was intentionally destroyed by recording and mastering
> engineers with the blessing of just about everybody. It was thought
> to be sonically irrelevant ("Bass is non-directional') and it could
> cause big problems for both producers and consumers.
Sure, but they really did not solve the problem at all in
the early days, because bass was still being reproduced by
spaced woofer systems that caused cancellation-related,
frequency-response anomalies. Mono subwoofers finally buried
that problem, and now you guys want to resuscitate the
thing.
> I now know that while bass IS non-directional, directionality is not
> the only kind of listening experience that stereo sub-bass conveys.
> While http://www.pcabx.com/technical/stereo_bass/index.htm may not
> be the best demo in the world (Dr. Feng says he is going to send me
> files for a better demo) it shows that stereo sub-bass does create a
> different listening experience. If one listens to these files using
> isolated headphones, which address the cancellation issues you raise,
> one still hears a difference.
Geez, Arny. What in blazes do special test tones, listened
to on headphones, have to do with the way speaker-equipped
audio systems handle low bass in typical home-listening
rooms, with commercially produced recordings?
> It's a freakin' DBT, Howard.
Hey, Arny, a good DBT will employ software and transducer
situations that have all the variables under control and
which also involve software that typical consumers will be
listening to. You are using special test signals, with
headphones, and I say that to prove a point you are ignoring
the real-world situations that real audio enthusiasts have
to deal with.
> Some day Howard you need to realize that a DBT is not like a
> benediction that we say to make things "holy audio".
I realize this. However, you are using a DBT to prove a
point by employing exotic test signals and rarely used
listening devices (headphones) to prove a point that is
irrelevant.
> DBTs are a reliable way to figure out if there is an audible
> difference. If a really good DBT says that there is no audible
> difference, then yes, there may not be an audible difference. But if
> the DBT says there is a audible difference, THEN THERE IS A
> DIFFERENCE AND WE NEED TO DEAL WITH IT!
Hey, Arny, I never said there would not be an audible
difference. When you go to dual low-bass producers you
introduce frequency-response and coherent-reinforcement
artifacts that do indeed make for a different sound from
what you get with a well-positioned mono sub. OK, you got me
there. Now how do you do a DBT with SPEAKERS, in REAL ROOMS,
with COMMERCIALLY PRODUCED RECORDINGS and sort out the
assorted other variables that will let you determine that
the differences you hear between a mono sub and stereo subs
(or even more subs in a surround-sound installation) and
actually prove that those differences are related to
low-bass spatiality?
> Howard, what is going to happen is:
>
> (1) Dr. Feng has promised to email me some test signals that are more
> representitive.
Hey, does this mean that they have been taken from
commercially produced recordings? Gee, Arny, I would think
that you had stuff like that right there in your own music
collection.
I'm going to audition them and if they seem useful to
> me, up they go at
> http://www.pcabx.com/technical/stereo_bass/index.htm .
>
> (2) Someplace along the way we'll find some recordings with stereo
> sub-bass that can be posted in excerpts and up they go at
> http://www.pcabx.com/technical/stereo_bass/index.htm .
Dig hard and deep. Remember, you will have to figure out a
way to counteract the coherent reinforcement that we get
with dual but spaced woofers down really low and will also
have to work out a way to filter out the suckout artifacts
that spaced woofers deliver at certain, driver-spacing
related, bass frequencies. If this is not done, you will
have to post specific instructions about how the speakers
have to be positioned to deal with those artifacts. You will
also have to indicate to people that they must ignore those
FR related artifacts and the spatiality artifacts being
produced at somewhat higher bass frequencies (coming from
the spaced full-range speakers) and listen only for
spatiality at very low frequencies. Good luck to you.
> Howard I preduct that just like you've done to date, you won't listen
> to them, and you'll prattle on indefinately about what a waste and
> snake oil stereo sub-bass is.
Gee, Arny. All you guys have done is used test tones and
headphones, and then you proclaim that what you hear with
those automatically applies to spaced speaker systems and
commercially available recordings. And people call me a fact
bender.
> > > > 2) He has not the means or material to test the hypothesis
> > >
> > > I think we've shown that the means and material can be delivered
> on a
> > > silver platter...
> > Easy. Just get some commercially produced recordings and do some
> > A/B comparisons. Of course, even then you have to take into
> > account the suckout interactions of dual subs, compared to a mono
> > sub, and have to handle the fact that dual subs will add
> > coherently below a certain frequency, which will enrich the low
> > bass with extra power.
> False claim on many grounds:
>
> (1) Stereo sub-bass is already known, by means of DBTs to be audible
> with isolated headphones where they are no suckouts and/or power
> level or frequency response issues.
This is crap. The vast majority of people listen on speakers
and any artifacts you claim exist will be buried under a
multitude of spatiality clues at higher frequencies and of
course those spaced woofer systems will impact the frequency
response in their own unique ways, and will therefore cause
the sound to be different from what a mono sub produces.
While you will gain a small amount in terms of low-bass
spatiality (which I do not believe most people would be able
to pinpoint at all), you lose low-bass frequency-response
accuracy.
Regarding your test tones, what you are doing is akin to
cranking up the gain when a CD is playing and pointing out
that at very low output levels some CD players have
distortion. It is inaudible at normal volume-setting levels,
but if you set up an atypical situation (cranking up the
gain as the signal output falls), you can hear those
artifacts. So, I guess that means that low-level distortion
with CD players is a serious problem, because if you crank
up the gain extremely high during very quiet musical
passages, you can hear grunge.
> (2) If you have multichannel bass, you obviously don't have the same
> signal coming out of both speakers, so the suck-outs you fear won't
> happen.
No matter how much "stereo" bass there might be, there will
also be plenty of mono bass and that bass will have the
artifacts I have noted.
> It seems obvious to me that one solution to the problem of
> mono bass or bass that is centrally imaged is (gasp) the center
> channel subwoofer.
Well, I do use one of those, but only because I have a
spare. Also, my old processor mixed center mid-bass into the
main channels and I used a center sub to alleviate that
problem. My present unit does not do this, but I retained
the sub for sentimental reasons. I did not use the center
sub during my comparisons, since I was only using two spaced
speakers.
> >I think that much of what you guys are hearing relates to those two
> phenomena.
>
> Since I've been clear about saying that the effect is clear with
> isolated headphones, I'm beginning to think that you are not catching
> all the relevant details in this debate.
No, you are not catching the details. You are setting up a
specialized experiment that is not relevant to what people
listen to and what they listen with.
> > > > 3) He conveniently ignores (1) and (2) to arrive at his
> > > conclusions.
> > > I think the conclusion was reached some time ago and has remained
> > > static.
> > Well, the laws of physics are immutable.
> They've always said that bass in a room is not mono.
Bass below what frequency? I certainly will admit that above
90 or so Hz we will get spatiality artifacts. Of course, in
a sub/sat system those frequencies are handled by the
satellites. And the spatial clues they generate are the main
item by far that delivers the sense of large-room space.
Howard Ferstler
Howard Ferstler
> How did JJ put it? Why do you want to lock people in to the oldest
> and most antiquated technology? Summed (mono) bass is an artifact
> that was necessary in the LP days. The recording medium has improved
> (wax cyl => 78 => LP => CD => ?).
For now what matters is what people can purchase. Are you
saying that most recordings are deficient, because they lack
stereo low bass?
> The recording equipment has improved
> (we're doing 16bit at up to 196kHz multi-channel here, and will soon have 24bit capability).
Except for the 5.1-channel option, I find this new
technology to be a waste of talent, money, and resources. It
probably will do more harm than good, as it alienates
consumers who just want to stick with what they have for a
while. I believe that both Dolby Digital (at 448 kbps) and
DTS are more than able to deal with all musical program
needs.
> Why not capture more of the sound in the performance venue than we did with LP?
We can. It is called 5.1-channel audio. Why sweat some minor
and probably inaudible low-bass artifacts when the real
action is the center and surround channels? Why chance
screwing up the uniformity of the low-bass frequency
response, just to get a near-inaudible improvement in
low-bass spatiality?
> Why stand in the face of progress?
Why not have meaningful progress? Why diddle with
trivialities?
> Why are you against commercial
> recordings that preserve the full bandwidth stereo signal? BTW,
> there is multi-channel bass on the master tapes. It only requires a
> re-mix to get that onto a CD. There are no technical reasons why all
> CD releases should not have stereo bass.
Hey, the discussion involves low bass. I have no objection
to stereo bass down to about 90 Hz. I think that is
essential.
> There's no reason why all
> new releases shouldn't have full bandwidth independent channel information.
Sure. Put it there. It cannot hurt anything. Of course, it
will not do much of anything below 90 Hz, or so.
> (snip)
> > Doing comparisons with a mono sub, vs some full-range
> > speakers with bass that was equal down to about 30 Hz, I
> > heard no differences with a variety of readily available
> > recordings.
> This is the final question to answer, e.g. what of the practical
> value of stereo bass. JJ says he has recordings (commercial) where
> it's readily noticable.
Yes. Well, it would only take him a few minutes to list
those discs. Then, you, I, and other concerned parties could
go shopping and see what we come up with. I await his list.
>You say you never hear any difference.
You are quite the perceptive one, aren't you.
> He is a internationally recognized expert on human hearing and
> audio. You are an armchair speculator that writes equipment/music
> reviews for consumer entertainment magazines.
Well pardon my lack of credentials and my inability to join
the audio elite. How is the air up there on Olympus?
One of the interesting things is the separation between the
technical guys like JJ (and maybe even you) and their
research and the assorted tweak journalists and tweak sales
clerks who spout stuff that consumers think is valid.
I try to bridge that gap, and realize that most consumers
are not particularly interested in hair-splitting details,
and I do not feel, as you guys apparently do, that being a
"popularizer" is somehow demeaning. At least it is not
demeaning if consumers are not steered into spending
wastefully. They want workable answers in language that they
can understand, and they want to know what works and what
does not.
What they do not want is mumbo jumbo of the kind that tells
them that megabuck wires, amps, and CD players are required
for good audio. While you and JJ may not like everything I
say, you probably will admit that I do not feed my readers a
bum steer when it comes to overkill products. Well, at
second thought, maybe feel that bum steers have their place,
and that I am the big party pooper. After all, if I had my
way a bunch of scam-related, high-end audio businesses would
fold - and good riddance.
> JJ has a wide variety
> of state of the art and readily available commercial recordings in
> stereo, digital dolby, and >2 channel, and a great lab for doing
> solid empirical testing. You have a home system that's been tweeked
> to your satisfaction. Who's judgement do you trust in matters of
> scientific opinion? Independent bass channels may indeed have no
> perceived value for you. You cannot extrapolate that to the
> rest of the world.
Well, I hear what I hear. I suggest that consumers do their
own comparisons and see what they come up with. Of course,
the psychological impact of having only one sub will
probably have them spending money for a second. I suppose
that JJ and you will at least end up having manufacturer
friends in the subwoofer business.
> > Note also that stereo bass transducers introduce
> > cancellation artifacts that a mono sub, placed in a corner,
> > will not produce. So, when comparing the frequency response
> Careful not to let yourself get too caught up in measurement
> details. In the end, only the realism of the reproduction
> is important, not how well distributed your bass nulls are in
> your particular room. Certainly, stereo bass presents real problems for
> accurate reproduction. Just as certainly, stereo bass can
> excite localization and spatial hearing cues. The former does
> not automatically justify ignoring the second.
Remember, we are talking about low bass, not bass in
general. I certainly will admit that bass from 90 Hz on up
should be in stereo. The question is: do we need stereo bass
down really low, while gaining new problems related to
inter-woofer cancellation artifacts?
> > > The only remaining point of interest to rao (exclusive of whether Howard possesses
> > > the ability to think logically) is whether or not a full bandwidth multi-channel
> > > recording, appropriately reproduced using full range spkrs, can provide additional,
> > > perceivable spatial sensations than cannot be reproduced by the same recording when
> > > reproduced over a 5.1 (single, mono-subwoofer) system.
> > The question for me is whether the other variables I noted
> > will have an impact when doing A/B comparisons of stereo vs
> > mono low-bass systems,
> Which you are not equiped to investigate given your description of your setup
> and hearing ability.
Well, forgive me for my limited hearing ability, and forgive
both me and most consumers for having substandard audio
systems. I never claim (as apparently you, Arny, and JJ do)
to be a golden ear. Yes, maybe my problem is that I do not
have stereo hearing. Hmmm. Now I know why all the sound
seems to be coming from the center all the time.
Much of the testing that you, JJ, and Arny have done appears
to be (and correct me if I am wrong) involved with
headphones and test tones. Now, perhaps tests of that kind
will deliver spatiality clues. Indeed, I am sure that with
the proper signals this will happen. However, once you begin
to use multiple speakers, and commercial recordings, and
satellites that are contributing spatiality clues above 90
Hz, and of course are using musical recordings instead of
test tones, you introduce variables that make it very, very
difficult to come to concrete conclusions about low-bass
spatiality.
> > and also whether this all matters
> > with the recordings people have available to purchase
> If people took your attitude, all audio electronics would have
> less than 50dB of inter-channel separation above 5kHz when LP's
> were the primary playback medium.
Well, have JJ (or Arny, or you) offer up some titles that
proves his (and your) point with musical program material.
> In truth, playback systems
> evolved considerably beyond the limitations of the LP (for the most
> part), and hence were able to readily take advantage of much of the
> increased capability of CD the instant it became available.
> To suggest that all systems be limited to the capabilities of
> the most widely available current source material is . . .
> how do I put it kindly ... well, it's plain stupid.
Let's have a list. If you can come up with one musical
recording that proves your point, I will concede. However,
proving that point will still be tricky, because we still
have the problem of frequency-response-related bass
interactions with spaced woofer systems (including coherent
reinforcement below a certain point when we switch from one
sub to two, even when there average levels are matched), as
well as the influence of spatial clues coming from the
satellites that will be there above 90 Hz. So it will be
nearly impossible to sort out spatiality differences by
simply listening to musical recordings.
Howard Ferstler
Arny Krueger
> Arny Krueger wrote:
> >
> > "Howard Ferstler" <fer...@attglobal.net> wrote in message
> > news:39B6F6C1...@attglobal.net...
>
> > > I am not the only person around who feels that a mono sub can
do
> > > the job just fine.
>
> > Howard, people use exactly the same argument for believeing that
LPs
> > are sonically transparent than CDs, and that tubed equipment is
> > necessarily more sonically transparent than SS, that kilobuck
speaker
> > wires sound better than far less expensive wires that are
properly
> > engineered, etc.
> At the risk of name dropping, Nousaine has written entire
> reviews and essays around the concept of single subwoofers,
> and he has backed up his findings with some pretty good
> research.
That was then, this is now.
>Perhaps he and the people he has used in his
> various comparison sessions were as wrong-headed and tin
> eared as you believe that I am.
That was then, this is now.
> Also, remember that many manufacturers offer a single sub
> output on their processors, and as of the last time I
> checked the LFE channel on both the Dolby Digital and DTS
> coding systems involved only one channel.
Dolby might change their tune, as it were.
>Yes, they are not
> particularly music oriented and there really is no reason
> for a sub with the musical coding itself, but in any case
> some people, somewhere, believe that a mono sub can do the
> job just fine. What's more, if what you guys say is true,
> the LFE explosions in movies would sound a lot better if
> there were two LFE channels, or even more. I guess Dolby and
> DTS got it wrong.
They did what was consistent with the best understandings of the day.
> > >The people who feel as I do have made use of commercially
available
> > recordings, I believe, rather than test
> > > signals that do not relate to what people can purchase in
record
> > stores.
> > Prove that the test signals are irrelevant to anything people buy
in
> > stores.
> Well, I heard no spatially related differences between a
> single sub and spaced woofer systems, using commercially
> produced recordings.
What, no suck-outs?
>With test-tone inputs, I did measure
> differences in terms of low-bass uniformity and cancellation
> artifacts, however. Perhaps those are what you guys are
> hearing when you do your particular comparisons.
What was unclear about it when I said "isolated headphones"?
>Guess what?
> They have nothing to do with the spatiality issue.
They may or they may not.
> > > > > >> Howard prefers to keep his head in the sand when his
> > beliefs
> > > > are put to the test <<
>
> > > > Wanna take a bet on how much time he's spent with any of the
> > tests at
> > > > www.pcabx.com?
> > > Wanna take a bet on how many recordings I have listened to
while
> > > switching back and forth between a mono sub and spaced woofer
> > > systems?
> > Howard, people use exactly the same argument for believeing that
LPs
> > are sonically transparent than CDs, and that tubed equipment is
> > necessarily more sonically transparent than SS, that kilobuck
speaker
> > wires sound better than far less expensive wires that are
properly
> > engineered, etc.
> Gee, Arny. Perhaps you did not read what I said carefully
> enough. I said that with commercially produced recordings I
> heard no spatiality advantages in the low bass, when
> comparing a mono sub (working below 80 Hz) to two full-range
> systems (flat to 30 Hz).
We know for sure that a great many commercial recordings are
intentially made with mono bass.
>You make it sound like I was
> listening for spiritual artifacts, the way that the crazies
> do when they listen to LP records and SET amps.
I think that this is the exact opposite direction.
>However,
> what I was listening for were spatiality differences and I
> heard none. The entire enterprise was a waste of time.
Could be that your experiment was poorly formed.
> > > > > >> Howard knows much less about live and recorded music
than
> > he realizes <<
> > > Tell that to the guys who gave my record-review books good
> > > reviews. Say, how many record reviews (books or magazine
> > > versions) have you guys published? I am not trying to demean
you,
> > > but in this case you have indicated that I do not know much
about
> > > live and recorded music, and yet I am the guy who went to the
> > > trouble to get the record-review books published. All you two
do
> > > is blowhard about your tests.
> > Howard, people use exactly the same argument for believing that
LPs
> > are sonically transparent than CDs, and that tubed equipment is
> > necessarily more sonically transparent than SS, that kilobuck
speaker
> > wires sound better than far less expensive wires that are
properly
> > engineered, etc.
> What kind of argument might that be? I am a record reviewer
> and I have compared using commercially produced recordings.
We know for sure that a great many commercial recordings are
intentially made with mono bass.
> You have used special test signals and maybe custom-made
> recordings and then have often compared using headphones.
We know for sure that a great many commercial recordings are
intentially made with mono bass.
> Well, just how much mono vs stereo bass comparing have you
> done using real speakers and subs in real rooms, with
> commercially produced recordings?
We know for sure that a great many present-day commercial recordings
are intentially made with mono bass.
> Have you bothered to sort
> out any additional variables that would involve the way
> multiple woofers would interact, in comparison to a single
> sub in a corner?
What was unclear about it when I said "isolated headphones"?
> Nobody has more respect for test signals than I do, but the
> last thing I do with them is to twist what I find with such
> signals to the extent that I overlay what I heard over what
> I believe most people would hear with recordings they
> purchase in stores.
We know for sure that a great many present-day commercial recordings
are intentially made with mono bass.
yes. That's the gist of
http://www.pcabx.com/technical/stereo_bass/index.htm .
>(2) that a similar phenomenon would
> be audible in home-listening rooms with commercially
> produced recordings?
We know for sure that a great many present-day commercial recordings
are intentially made with mono bass.
> > Our sound systems reproduce the differences in the upper bass,
> > midrange, and treble. Single subwoofer systems don't reproduce
the
> > differences in the lower bass. I've proven to my satisfaction
with a
> > DBT that there is an added audible dimension to bass that strikes
the
> > ears with differing phases even with isolated headphones.
> I will not deny that differences might be audible with
> headphones. However, in a typical listening room, with
> speakers, you have those frequency-response variables to
> deal with, not to mention the spatial clues being delivered
> at the same time by higher frequencies coming from the
> satellites, and those are nearly impossible to sort out when
> comparing a single low-bass transducer and a pair of them.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> I will also not deny that with special test signals they
> might be audible. However, I am dealing with real-world
> recordings and I am telling you that a mono sub, if crossed
> over low enough (below 90 Hz, actually) will just not have a
> problem. The mass of spatiality clues delivered by the
> satellites above 90 Hz will just overwhelm any low-bass
> spatiality artifacts.
We know for sure that a great many present-day commercial recordings
are intentially made with mono bass.
> > With
> > isolated headphones there is no reinforcement or cancellation in
my
> > listening room because my listening room is not involved.
> So what? Most people do not listen with headphones. They
> listen with speakers in typical rooms, and they listen to
> commercially produced recordings that have a plethora of
> spatiality clues above the low-bass range that smother any
> minor spatiality clues delivered by spaced woofer systems.
> In addition, spaced woofer systems present problems of their
> own that a mono sub, properly located, will not have.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> So, in order to correct one very minor problem, you are
> willing to put up with a bigger one. Count me out.
That means that you are not the winner of this wrestling match.
Johnson, Feng and Krueger are.
> > Its a classic chicken-and-egg situation.
> > Because LPs can't handle stereo sub-bass very well (they don't
handle
> > mono sub-bass very well, either) the audio industry for over 40
years
> > has been treating stereo sub-bass like it was the plague.
> Well, if there are any mono complements to the bass signals
> at all you are possibly going to have interactions that
> certainly are a potential problem. A mono sub, properly
> positioned and properly crossed over bypasses those
> problems. Now, in order to deliver subtle spatiality clues
> down really low, you are going to reintroduce the
> woofer-interaction problem.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> > Stereo
> > sub-bass was intentionally destroyed by recording and mastering
> > engineers with the blessing of just about everybody. It was
thought
> > to be sonically irrelevant ("Bass is non-directional') and it
could
> > cause big problems for both producers and consumers.
> Sure, but they really did not solve the problem at all in
> the early days, because bass was still being reproduced by
> spaced woofer systems that caused cancellation-related,
> frequency-response anomalies. Mono subwoofers finally buried
> that problem, and now you guys want to resuscitate the
> thing.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> > I now know that while bass IS non-directional, directionality is
not
> > the only kind of listening experience that stereo sub-bass
conveys.
> > While http://www.pcabx.com/technical/stereo_bass/index.htm may
not
> > be the best demo in the world (Dr. Feng says he is going to send
me
> > files for a better demo) it shows that stereo sub-bass does
create a
> > different listening experience. If one listens to these files
using
> > isolated headphones, which address the cancellation issues you
raise,
> > one still hears a difference.
> Geez, Arny. What in blazes do special test tones, listened
> to on headphones, have to do with the way speaker-equipped
> audio systems handle low bass in typical home-listening
> rooms, with commercially produced recordings?
They show that the effect is reliably audible without necessarily
creating directional cues.
> > It's a freakin' DBT, Howard.
> Hey, Arny, a good DBT will employ software and transducer
> situations that have all the variables under control and
> which also involve software that typical consumers will be
> listening to.
That is only true if there is a certain list of variables to control
and we stipulate that we will use typical present-day consumer
software. Multichannel Bass is a SOTA topic. Therefore off-the-shelf
present day recordings are not going to be made with it in mind. Like
I said, "Chicken and Egg". The obvious way to break the Chicken and
Egg conundrum is to bring in your own chicken or egg.
>You are using special test signals, with
> headphones, and I say that to prove a point you are ignoring
> the real-world situations that real audio enthusiasts have
> to deal with.
I'm saying that you can't let conventions that date back to the LP
limit what you plan to do in the future.
> > Some day Howard you need to realize that a DBT is not like a
> > benediction that we say to make things "holy audio".
> I realize this. However, you are using a DBT to prove a
> point by employing exotic test signals and rarely used
> listening devices (headphones) to prove a point that is
> irrelevant.
If I had some good program material at hand to demonstrate it, do you
think I would not post it? It's a chicken and egg problem. One step
is to show that the effect is audible. That's a done deal. Now we
figure out how to get some musical program material to demonstrate it
with.
> > DBTs are a reliable way to figure out if there is an audible
> > difference. If a really good DBT says that there is no audible
> > difference, then yes, there may not be an audible difference. But
if
> > the DBT says there is a audible difference, THEN THERE IS A
> > DIFFERENCE AND WE NEED TO DEAL WITH IT!
> Hey, Arny, I never said there would not be an audible difference.
So that makes this a far different case than designer wires, right?
>When you go to dual low-bass producers you
> introduce frequency-response and coherent-reinforcement
> artifacts that do indeed make for a different sound from
> what you get with a well-positioned mono sub.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> OK, you got me
> there. Now how do you do a DBT with SPEAKERS, in REAL ROOMS,
> with COMMERCIALLY PRODUCED RECORDINGS and sort out the
> assorted other variables that will let you determine that
> the differences you hear between a mono sub and stereo subs
> (or even more subs in a surround-sound installation) and
> actually prove that those differences are related to
> low-bass spatiality?
Make a system that switches back and forth between the two modes of
operation. I think I can do it all with just line-level switching.
> > Howard, what is going to happen is:
> >
> > (1) Dr. Feng has promised to email me some test signals that are
more
> > representitive.
> Hey, does this mean that they have been taken from
> commercially produced recordings? Gee, Arny, I would think
> that you had stuff like that right there in your own music
> collection.
When I have the time I'll go looking for it. Meanwhile remember that
"isolated headphones" can constitute a relevant test.
We know for sure that a great many present-day commercial recordings
are intentially made with mono bass.
> > I'm going to audition them and if they seem useful to
> > me, up they go at
> > http://www.pcabx.com/technical/stereo_bass/index.htm .
<note: they were and they are posted>
> > (2) Someplace along the way we'll find some recordings with
stereo
> > sub-bass that can be posted in excerpts and up they go at
> > http://www.pcabx.com/technical/stereo_bass/index.htm .
> Dig hard and deep. Remember, you will have to figure out a
> way to counteract the coherent reinforcement that we get
> with dual but spaced woofers down really low and will also
> have to work out a way to filter out the suckout artifacts
> that spaced woofers deliver at certain, driver-spacing
> related, bass frequencies.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass... and... remember that
"isolated headphones" can constitute a relevant test.
>If this is not done, you will
> have to post specific instructions about how the speakers
> have to be positioned to deal with those artifacts. You will
> also have to indicate to people that they must ignore those
> FR related artifacts and the spatiality artifacts being
> produced at somewhat higher bass frequencies (coming from
> the spaced full-range speakers) and listen only for
> spatiality at very low frequencies. Good luck to you.
SOTA application. Meanwhile we know that its audible under ideal
conditions, which is one thing that is not true for "designer wires".
> > Howard I preduct that just like you've done to date, you won't
listen
> > to them, and you'll prattle on indefinately about what a waste
and
> > snake oil stereo sub-bass is.
> Gee, Arny. All you guys have done is used test tones and
> headphones, and then you proclaim that what you hear with
> those automatically applies to spaced speaker systems and
> commercially available recordings. And people call me a fact
> bender.
It may not apply to currently-availble commerically available
recordings because we know for sure that a great many present-day
commercial recordings are intentially made with mono bass.
> > > > > 2) He has not the means or material to test the hypothesis
> > > >
> > > > I think we've shown that the means and material can be
delivered
> > on a
> > > > silver platter...
>
> > > Easy. Just get some commercially produced recordings and do
some
> > > A/B comparisons. Of course, even then you have to take into
> > > account the suckout interactions of dual subs, compared to a
mono
> > > sub, and have to handle the fact that dual subs will add
> > > coherently below a certain frequency, which will enrich the low
> > > bass with extra power.
>
> > False claim on many grounds:
> >
> > (1) Stereo sub-bass is already known, by means of DBTs to be
audible
> > with isolated headphones where they are no suckouts and/or power
> > level or frequency response issues.
> This is crap. The vast majority of people listen on speakers
> and any artifacts you claim exist will be buried under a
> multitude of spatiality clues at higher frequencies and of
> course those spaced woofer systems will impact the frequency
> response in their own unique ways, and will therefore cause
> the sound to be different from what a mono sub produces.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> While you will gain a small amount in terms of low-bass
> spatiality (which I do not believe most people would be able
> to pinpoint at all), you lose low-bass frequency-response
> accuracy.
Not necessarily. If multiple subwoofers were used only one at a time
to create the impression of spatial sub bass...
> Regarding your test tones, what you are doing is akin to
> cranking up the gain when a CD is playing and pointing out
> that at very low output levels some CD players have
> distortion.
However with properly dithered CDs (which abound) no good CD player
(which abound) has this kind of distortion. The signal just fades
into the noise.
>It is inaudible at normal volume-setting levels,
> but if you set up an atypical situation (cranking up the
> gain as the signal output falls), you can hear those
> artifacts.
The test tones from Mr. Feng are at -14 dB FS which is hardly
"crank(ed) up".
>So, I guess that means that low-level distortion
> with CD players is a serious problem, because if you crank
> up the gain extremely high during very quiet musical
> passages, you can hear grunge.
However with properly dithered CDs (which abound) no good CD player
(which abound) has this kind of distortion. The signal just fades
into the noise.
> > (2) If you have multichannel bass, you obviously don't have the
same
> > signal coming out of both speakers, so the suck-outs you fear
won't
> > happen.
> No matter how much "stereo" bass there might be, there will
> also be plenty of mono bass and that bass will have the
> artifacts I have noted.
How do you know that for sure, hampered as you are by the fact that
you only have access to current technology CDs. Remember, we are
talking about something that could be done within the current CD
standard.
> > It seems obvious to me that one solution to the problem of
> > mono bass or bass that is centrally imaged is (gasp) the center
> > channel subwoofer.
<snip>
> > >I think that much of what you guys are hearing relates to those
two
> > phenomena.
> > Since I've been clear about saying that the effect is clear with
> > isolated headphones, I'm beginning to think that you are not
catching
> > all the relevant details in this debate.
> No, you are not catching the details. You are setting up a
> specialized experiment that is not relevant to what people
> listen to and what they listen with.
What they have today and listen to today. Advancing the SOTA means
changing things, no?
> > > > > 3) He conveniently ignores (1) and (2) to arrive at his
> > > > conclusions.
>
> > > > I think the conclusion was reached some time ago and has
remained
> > > > static.
> > > Well, the laws of physics are immutable.
> > They've always said that bass in a room is not mono.
> Bass below what frequency?
Pick one or many.
>I certainly will admit that above
> 90 or so Hz we will get spatiality artifacts. Of course, in
> a sub/sat system those frequencies are handled by the
> satellites. And the spatial clues they generate are the main
> item by far that delivers the sense of large-room space.
Arny sits here thinking about old dogs and new tricks. ;-)
Howard Ferstler
>
>
> Arny and Tom bring up a good point (as does Howard).
> Despite the facts about LF perception, the question
> remains (in rao) about the real-world perceivability
> and value of full bandwidth multi-channel reproduction.
>
> How many of you have a full bandwidth (okay, flat to 40Hz)
> 5 channel setup, and have compared it to the same
> with a good HP to the 5 in 5.1 using full bandwidth
> multi-channel source material (movie sound tracks included)?
The best I have done is comparing two up front (flat in the
room to 30 Hz) with a big sub (flat to 20 Hz). My center
only responds flat to about 70 Hz, and so I normally use an
additional sub (flat to 20 Hz, again) with it. My four
surrounds are only flat to about 50 Hz.
What I intend to do is adjust the sub for a THX-style
rolloff (the Velodyne F1800RII has a 15-Hz/35-Hz rolloff
switch) and do the comparing that way. In that case, both
the dual woofer and mono sub outputs should be similar in
terms of rolloff points down really low.
Of course, the dual woofers will still add coherently down
really low, even with the average bass levels matched, and
will still have slight depressions at about 56 Hz and 67 Hz,
due to their 12-foot spacing and the 5-foot distances of
each to the two side walls. Using a mono sub in a corner,
crossed over steeply at 90 Hz, eliminates such artifacts,
and so there will be frequency-response related differences
because of that.
Howard Ferstler
Dr. B. J. Feng
Howard Ferstler wrote:
> (snip)
> For now what matters is what people can purchase. Are you
> saying that most recordings are deficient, because they lack
> stereo low bass?
Would you have said that mono recordings were deficient because they
lacked localization information? Would you have said that LP recordings
were deficient because of their limited dynamic range? Would you have said
that CD's were deficient because they do not provide for >2 channels of independent
information?
Tell me again what your point was. It is beyond argument that
multi-channel, independent bass tracks would provide location/spatial
cues that summed mono-bass tracks cannot (independent of how useful
this would be on any particular recording). It would convey
more acoustic information of the original live performance to the
listener. How can you be so adamantly opposed to this?
> > Why not capture more of the sound in the performance venue than we did with LP?
>
> We can. It is called 5.1-channel audio. Why sweat some minor
> and probably inaudible low-bass artifacts when the real
> action is the center and surround channels?
You are committing the same faults of logic that many others have
already pointed out to you. You do not have any true 5.1 music
recordings nor do you have a full range 5 speaker playback system.
Therefore, you cannot possibly know how minor or inaudible these
LF spatial cues are. Even when you do someday get to hear such
a thing, your judgement will be biased by your particular, and unique
set of values -- values that are firmly set against technical progress.
>Why chance
> screwing up the uniformity of the low-bass frequency
> response, just to get a near-inaudible improvement in
> low-bass spatiality?
That sounds a lot like some of the arguments that came out
against stereo many decades ago. Congratulations on embracing the
same head-in-the-sand philosophy that keeps some people saying that
mono is better than stereo. You are no different than the "stereo
is the ultimate" people that you attack. Years from now when
the rest of us are playing true 5 channel music recordings on
5 full bandwidth systems, you'll still be spitting in the wind
with your Dolby Digital 5.1 is sufficient gibberish.
(snip)
> > This is the final question to answer, e.g. what of the practical
> > value of stereo bass. JJ says he has recordings (commercial) where
> > it's readily noticable.
>
> Yes. Well, it would only take him a few minutes to list
> those discs. Then, you, I, and other concerned parties could
> go shopping and see what we come up with. I await his list.
He actually posted a specific track of a specific album for you.
Do you recall your response?
(snip)
> Well pardon my lack of credentials and my inability to join
> the audio elite. How is the air up there on Olympus?
Lack of credentials is fine. Lack of knowledge is what will
keep you stuck in the old fashioned muck of surround sound
processing long after most people have moved into the next
paradigm of audio reproduction.
(snip)
> While you and JJ may not like everything I
> say, you probably will admit that I do not feed my readers a
> bum steer when it comes to overkill products.
right, and at the same time you certainly do feed them
a bum steer when it comes to any new technology that
can actually improve the realism of music reproduction.
This thread is an excellent example of such.
>
> > Which you are not equiped to investigate given your description of your setup
> > and hearing ability.
>
> Well, forgive me for my limited hearing ability,
I was not refering to your hearing ability but to your equipment limitations.
> I never claim (as apparently you, Arny, and JJ do)
> to be a golden ear.
Lose the false accusations. It'll do wonders for your rao credibility with
kooks like JJ and me.
>
> Much of the testing that you, JJ, and Arny have done appears
> to be (and correct me if I am wrong) involved with
> headphones and test tones.
Sure, you're wrong.
> > If people took your attitude, all audio electronics would have
> > less than 50dB of inter-channel separation above 5kHz when LP's
> > were the primary playback medium.
>
> Well, have JJ (or Arny, or you) offer up some titles that
> proves his (and your) point with musical program material.
Proof that you still don't understand much of what JJ posts.
John
jj, curmudgeon and tiring philalethist
Dr. B. J. Feng <bf...@attglobal.net> wrote:
>How many of you have a full bandwidth (okay, flat to 40Hz)
>5 channel setup, and have compared it to the same
>with a good HP to the 5 in 5.1 using full bandwidth
>multi-channel source material (movie sound tracks included)?
ME!
I do. I did!
--
Copyright j...@research.att.com 2000, 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.
Howard Ferstler
>
> "Howard Ferstler" <hfer...@mailer.fsu.edu> wrote in message
> news:39B7C36E...@mailer.fsu.edu...
> > Well, I heard no spatially related differences between a
> > single sub and spaced woofer systems, using commercially
> > produced recordings.
> What, no suck-outs?
Those impact frequency response, not spatiality. However, in
some cases the difference might be interpreted wrongly.
Certainly, the soundfield will be different.
> > Gee, Arny. Perhaps you did not read what I said carefully
> > enough. I said that with commercially produced recordings I
> > heard no spatiality advantages in the low bass, when
> > comparing a mono sub (working below 80 Hz) to two full-range
> > systems (flat to 30 Hz).
> We know for sure that a great many commercial recordings are
> intentially made with mono bass.
Well, I leave it to you guys to come up with some titles
(and stock numbers, so that they can easily be ordered by
me) that reflect the current state of the stereo-low-bass
art.
> >However,
> > what I was listening for were spatiality differences and I
> > heard none. The entire enterprise was a waste of time.
> Could be that your experiment was poorly formed.
As poorly formed as experiments that use headphones and test
signals to come to conclusions about how stereo woofers will
sound in terms of low-bass spatiality with musical program
material in typical home-listening rooms? There may be some
ability to perceive stereo low bass when signals exist in
isolation (and considering the use of headphones, the ears
also are put in isolation), but is the phenomenon audible
with musical program material listened to on speaker
systems?
> > Geez, Arny. What in blazes do special test tones, listened
> > to on headphones, have to do with the way speaker-equipped
> > audio systems handle low bass in typical home-listening
> > rooms, with commercially produced recordings?
> They show that the effect is reliably audible without necessarily
> creating directional cues.
Well, the additional impact on response uniformity and
reinforcement down really low, plus the impact of spatial
clues at higher frequencies, might must thoroughly
overshadow low-bass spatiality artifacts. How do we sort
things out so that we can be sure that what you guys say
about low-bass spatiality is true? There is only one way
that I know of. We would have to actually put the musical
test signals on the recording and have the recording itself
generate either stereo low bass sent to two subs or mono low
bass signals sent to just one. With proper equalization,
that could at least compensate for coherent reinforcement
down really low when two subs were working. However, even
then you would have problems with suckout artifacts that are
related to the spacing between the dual subs. Then, the
signals to the satellites would have to be in mono, with
only the bass in stereo.
The disc itself would then switch between mono low bass and
stereo low bass, while the signals above 90 Hz were always
left in mono. Then, the listener could judge whether the
stereo low bass was having any impact on the sense of
spatiality. Of course, even then it could be said that
typical spatiality above 90 Hz with full-stereo recordings
still has a manifestly stronger impact than any stereo-bass
artifacts.
In other words, this is an almost impossible situation if we
are talking about making practical comparisons with musical
program material. There are too many hard to filter out
variables when we deal with musical program material.
> > > It's a freakin' DBT, Howard.
> > Hey, Arny, a good DBT will employ software and transducer
> > situations that have all the variables under control and
> > which also involve software that typical consumers will be
> > listening to.
> That is only true if there is a certain list of variables to control
> and we stipulate that we will use typical present-day consumer
> software. Multichannel Bass is a SOTA topic. Therefore off-the-shelf
> present day recordings are not going to be made with it in mind. Like
> I said, "Chicken and Egg". The obvious way to break the Chicken and
> Egg conundrum is to bring in your own chicken or egg.
But the chicken or egg has to involve music, and if you use
music you are going to be faced with the stereo ambiance
signals that will also be coming from the satellites at
frequencies above 90 Hz. Those will certainly make it harder
to spot those low-bass spatiality clues. I think it will be
a lot harder.
> If I had some good program material at hand to demonstrate it, do you
> think I would not post it? It's a chicken and egg problem. One step
> is to show that the effect is audible. That's a done deal.
With special test tones and perhaps headphones it is
audible. But proving that it is significantly audible with
musical program material is difficult. Not only because of
the strong influence of spatiality clues coming from the
satellites above about 90 Hz, but also because of the
frequency-response differences between a mono sub and a pair
of spaced subs, even if average bass levels are equalized.
> Now we
> figure out how to get some musical program material to demonstrate it
> with.
Feng says that JJ knows of some appropriate titles.
> We know for sure that a great many present-day commercial recordings
> are intentially made with mono bass.
You have said this a number of times, but I need to point
out that a fair number of classical releases are done with
spaced pairs, and some of the early Telarc releases used
very widely spaced pairs, with a fill mike in between. The
Decca Tree also involves spaced microphones. All recordings
made by those techniques should have stereo bass.
Ironically, seriously purist recordings made with coincident
microphones or ORTF arrays probably do not have much in the
way of stereo in the low bass. Yet it is often those
recordings (most of which are classical) that are lionized
by audio purists.
> > No matter how much "stereo" bass there might be, there will
> > also be plenty of mono bass and that bass will have the
> > artifacts I have noted.
> How do you know that for sure, hampered as you are by the fact that
> you only have access to current technology CDs. Remember, we are
> talking about something that could be done within the current CD
> standard.
And as I have noted, a number of classical releases have
been made with spaced microphones. Those would have stereo
bass as a matter of policy. In addition, many highly
regarded purist recordings have been done with ORTF and
coincident microphones, and those would have little in the
way of stereo bass. At higher frequencies, those recordings
are very spacious, and that seems to be more than adequate
for those purists.
Howard Ferstler
Howard Ferstler
>
> > (snip)
> > For now what matters is what people can purchase. Are you
> > saying that most recordings are deficient, because they lack
> > stereo low bass?
> Would you have said that mono recordings were deficient because they
> lacked localization information? Would you have said that LP recordings
> were deficient because of their limited dynamic range? Would you have said
> that CD's were deficient because they do not provide for >2 channels of independent
> information?
>
> Tell me again what your point was. It is beyond argument that
> multi-channel, independent bass tracks would provide location/spatial
> cues that summed mono-bass tracks cannot (independent of how useful
> this would be on any particular recording). It would convey
> more acoustic information of the original live performance to the
> listener. How can you be so adamantly opposed to this?
Because many classical recordings (the spaced-omni produced
early Telarcs, Decca/London releases done with the Decca
Tree, Delos releases done with an ORTF array in combination
with a pair of spaced omni microphones to allow for some
additional "bloom," and even most Gothic Records organ
recordings), are already done with microphones that deliver
a degree of stereo bass, probably even down to fairly deep
frequencies. I hear no loss in hall ambiance when those
items are played back with a mono sub.
> > We can. It is called 5.1-channel audio. Why sweat some minor
> > and probably inaudible low-bass artifacts when the real
> > action is the center and surround channels?
> You are committing the same faults of logic that many others have
> already pointed out to you. You do not have any true 5.1 music
> recordings
Well, John, you need to catch up on current events. I have
reviewed a fair number of Dolby Digital and DTS recordings
for The Sensible Sound.
> nor do you have a full range 5 speaker playback system.
Well, you do have me there. My four surrounds only go down
strongly to 50 Hz and my center is only strong to 70 Hz
(normally, it gets its own sub, flat to 20 Hz). However, my
mains are strong down to 30 Hz (when I use my second sub,
the response of the surround and main channels goes to 20
Hz, via that sub), and when I compare the 30-Hz mains
running full range to the sub crossed over steeply at 90 Hz,
the sub-assisted version actually has MORE spatiality,
because the sub is flat to 20 Hz and that extra extension
adds a degree of bigness to the sound. Now *that* is
spatiality.
> Therefore, you cannot possibly know how minor or inaudible these
> LF spatial cues are.
Neither can you, since whenever you start stacking on
additional subwoofers to each channel you introduce
additional frequency-response-related artifacts. These
additional variables make meaningful direct comparisons
nearly impossible.
> Even when you do someday get to hear such
> a thing, your judgement will be biased by your particular, and unique
> set of values -- values that are firmly set against technical progress.
Hey, John. In my magazine articles and even right here I
have been an overwhelmingly strong advocate of surround
sound, particularly as it relates to a workable, discrete
center channel and discrete surrounds. I also have
championed Dolby Digital and even DTS for music
reproduction. I think that the industry is headed off on a
wild-goose chase with this DVD-A and SACD stuff, by the way.
They will pay a price for their waste of time.
> >Why chance
> > screwing up the uniformity of the low-bass frequency
> > response, just to get a near-inaudible improvement in
> > low-bass spatiality?
> That sounds a lot like some of the arguments that came out
> against stereo many decades ago.
Stereo was anything but a near-inaudible improvement.
> Congratulations on embracing the
> same head-in-the-sand philosophy that keeps some people saying that
> mono is better than stereo. You are no different than the "stereo
> is the ultimate" people that you attack. Years from now when
> the rest of us are playing true 5 channel music recordings on
> 5 full bandwidth systems,
...and doing battle with bass-interaction artifacts and not
winning, and of course spending huge amounts on multiple
subwoofers....
> you'll still be spitting in the wind
> with your Dolby Digital 5.1 is sufficient gibberish.
It is fully sufficient. So is DTS. They both work fine, and
it is pointless to bring out another format that will just
alienate consumers.
> (snip)
> > > This is the final question to answer, e.g. what of the practical
> > > value of stereo bass. JJ says he has recordings (commercial) where
> > > it's readily noticable.
> > Yes. Well, it would only take him a few minutes to list
> > those discs. Then, you, I, and other concerned parties could
> > go shopping and see what we come up with. I await his list.
> He actually posted a specific track of a specific album for you.
> Do you recall your response?
I need to see it again. As I have noted elsewhere, Telarc
produced a number of recordings with spaced microphones some
time back and the Decca Tree has always had spaced
microphones. Gothic also mostly uses spaced mikes with their
classical recordings, and Delos, although they frequently
use an ORTF array, also incorporates spaced-omni mikes out
at the sides to add some bloom. They also use space omnis
for some of their organ releases. So, stereo *low* bass is
not all that uncommon, and I have listened to a lot of it. I
am not impressed.
> (snip)
> > Well pardon my lack of credentials and my inability to join
> > the audio elite. How is the air up there on Olympus?
> Lack of credentials is fine. Lack of knowledge is what will
> keep you stuck in the old fashioned muck of surround sound
> processing long after most people have moved into the next
> paradigm of audio reproduction.
We shall see, John.
> (snip)
> > While you and JJ may not like everything I
> > say, you probably will admit that I do not feed my readers a
> > bum steer when it comes to overkill products.
> right, and at the same time you certainly do feed them
> a bum steer when it comes to any new technology that
> can actually improve the realism of music reproduction.
> This thread is an excellent example of such.
Well, prove it with musical material and now with isolated
test tones listened to with headphones. I will not hold my
breath.
> > > Which you are not equiped to investigate given your description of your setup
> > > and hearing ability.
> > Well, forgive me for my limited hearing ability,
> I was not refering to your hearing ability but to your equipment limitations.
Well forgive me for having a cheap audio rig.
> > I never claim (as apparently you, Arny, and JJ do)
> > to be a golden ear.
> Lose the false accusations. It'll do wonders for your rao credibility with
> kooks like JJ and me.
Being an RAO regular, I am plenty used to kooks.
> > Much of the testing that you, JJ, and Arny have done appears
> > to be (and correct me if I am wrong) involved with
> > headphones and test tones.
> Sure, you're wrong.
OK, fill me in. No test tones and no headphones. What kind
of speakers, what kind of sub, what kind of room, and what
kind of musical recordings have you guys been using? How do
you deal with frequency-response-uniformity problems when
you cut in that second (or third or fourth) sub during your
comparisons?
Howard Ferstler
Howard Ferstler
>
> >
> (snip)
>
> > Of course, the dual woofers will still add coherently down
> > really low,
>
> If there is incoherent stereo bass info in the program material,
> those woofers do not add coherently (except in the time avergaged
> frequency domain -- which is a very poor indicator of how humans
> perceive music).
>
> John
Even a recording with stereo bass will have some mono-bass
artifacts, and those will add coherently. This will add a
degree of richness and fullness down really low.
Howard Ferstler
Nousaine
>already pointed out to you. You do not have any true 5.1 music
>recordings nor do you have a full range 5 speaker playback system.
>Therefore, you cannot possibly know how minor or inaudible these
>LF spatial cues are. Even when you do someday get to hear such
>a thing, your judgement will be biased by your particular, and unique
>set of values -- values that are firmly set against technical progress.
I have the full range capability. Need recordings.
>>Why chance
>> screwing up the uniformity of the low-bass frequency
>> response, just to get a near-inaudible improvement in
>> low-bass spatiality?
>
>That sounds a lot like some of the arguments that came out
>against stereo many decades ago. Congratulations on embracing the
>same head-in-the-sand philosophy that keeps some people saying that
>mono is better than stereo. You are no different than the "stereo
>is the ultimate" people that you attack. Years from now when
>the rest of us are playing true 5 channel music recordings on
>5 full bandwidth systems, you'll still be spitting in the wind
>with your Dolby Digital 5.1 is sufficient gibberish.
> (snip)
>> > This is the final question to answer, e.g. what of the practical
>> > value of stereo bass. JJ says he has recordings (commercial) where
>> > it's readily noticable.
>>
>> Yes. Well, it would only take him a few minutes to list
>> those discs. Then, you, I, and other concerned parties could
>> go shopping and see what we come up with. I await his list.
>
>He actually posted a specific track of a specific album for you.
>Do you recall your response?
I must have missed that one. I'm still looking for a reference to program
material.
Need those myself.
Nousaine
>
> Tell me again what your point was. It is beyond argument that
> multi-channel, independent bass tracks would provide location/spatial
> cues that summed mono-bass tracks cannot (independent of how useful
> this would be on any particular recording). It would convey
> more acoustic information of the original live performance to the
> listener. How can you be so adamantly opposed to this?
I don't think that this is beyond argument. You maybe able to record it but you
may not be able to convey it to the listener in the best manner. As far as I
can see no one is addressing the real problem of spaced low frequency drivers
in a listening room.
I'm all for progress and have addressed the issue of multichannel in great
detail (AES Preprint 4558, Multiple Subwoofers for Home Theater). As far as I
can see the response variations induced by failure to excite some room modes of
spaced subwoofers might swamp these cues.
I've also done the Lexicon "Bass Enhancement" thing where surround channels are
driven 90 degrees out of phase in an effort to improve spaciousness and
envelopment.
Bass Enhance does sound different (mostly because of the large response notch
introduced at 80 Hz, I suspect) but it does not improve spaciousness or
envelopment in my subjective opinion.
This technique attempts to assign "stereo bass" to the recording even if it is
not present in the original. I have found precious few recordings that have
out-of-phase information at lower frequencies so some program references would
be very helpful.
Arny Krueger
"Nousaine" <nous...@aol.com> wrote in message
news:20000907172425...@ng-ch1.aol.com...
> >> Well, have JJ (or Arny, or you) offer up some titles that
> >> proves his (and your) point with musical program material.
> Need those myself.
I'm not sure that anybody knows how to make them will talk or release
something that will let the cat out of the bag.
I think that the comment: "Well, we've had spaced microphone
recordings for a long time", miss the point.
Recording practice has suffered for a long time from the idea that we
could somehow position microphones in a room on say, some kind of
regular grid, and then play what those microphones pick up through
(omnidirectional?) speakers on the same grid and have some kind of
realism.
Multichannel bass might be the situation where the fallacy of this
approach becomes most obvious.
If I were going to make a multichannel bass recording, I would
remember that my goal is not to record the sound field at a certain
point in the room where the live performance happens, but rather to
play back something that will stimulate that sound field at the
corresponding point in the listening room. I think that particularly
with sub-bass the degree to which these two things are vastly
differnet becomes most clear.
Hob...@in.gum.tree
<bf...@attglobal.net> wrote:
>Dear RAO Freaks,
>
>I've been away "doing the work" so I'm really late to this
>thread. Saw Arnyk's post about generating the signal.
>Arny -- it's NOT a fixed offset but a phase modulation
>that JJ is talking about.
>
>I've generated a 10 second .wav file that shows the
>localization effect of a 2hz phase modulation
>(I think it was 0.1 radian peak modulation). If anyone
>wants it, I can email it out. Best if I can email it
>to someone who has a >28.8k connection for further distribution
>(that's all I can get thru my local telco).
>
>
>Dave, etal. With all due respect, there are a few
>points you guys are ignoring:
>
Ello, ello. It is I, Howardson Etal. I am in a new disguise since my
cover was blown by The Fox.
Welcome, Ben! Have fun. LOTS!
It aint be babe doing the ingoring.... I have not argued against
recording or reproducing stereo bass. "when something's not right it's
wrong"
Byeeeeee.
>1) In the "real" venue one can have wave propagation at low frequencies.
> Hence, "stereo" bass does indeed exist in a real life music performance.
> This is true for classical, jazz, and pop performances.
>
> >> Howard is wrong <<
>
>2) There is excellent scientific/empirical evidence that low frequency signals
> can contribute to spatial localization and spatial sensation (JJ already
> pointed everyone to the BMLD work, go read some of it).
>
> >> Howard disbelief stems from his usual lack of knowledge <<
>
>(these two points are enough to call into question the idea of using 1 subwoofer
> and mono bass if the goal is the most lifelike recreation of the concert experience).
>
>3) Point 2 is easily proven via the test JJ suggested
>
> >> Howard prefers to keep his head in the sand when his beliefs are put to the test <<
>
>4) Point 1 is easily proven by anyone who's done a few live recordings and then
> examined the recorded signal (OLD OLD work, Howard).
>
> >> Howard knows much less about live and recorded music than he realizes <<
>
>
>The only remaining point of interest to rao (exclusive of whether Howard possesses
>the ability to think logically) is whether or not a full bandwidth multi-channel
>recording, appropriately reproduced using full range spkrs, can provide additional,
>perceivable spatial sensations than cannot be reproduced by the same recording when
>reproduced over a 5.1 (single, mono-subwoofer) system.
>
>Howard cannot logically speak to this because:
>1) He has an incredibly strong bias against the hypothesis
>2) He has not the means or material to test the hypothesis
>3) He conveniently ignores (1) and (2) to arrive at his conclusions.
>
>With Kind Regards,
>
>John Feng
Bollocks!
"THE mark of quality assurance", note.
"Bollocks" is a trademark of Gum.tree Opinions
Howard Ferstler
>
> In article <39B7A7DE...@attglobal.net>,
> Dr. B. J. Feng <bf...@attglobal.net> wrote:
> >How many of you have a full bandwidth (okay, flat to 40Hz)
> >5 channel setup, and have compared it to the same
> >with a good HP to the 5 in 5.1 using full bandwidth
> >multi-channel source material (movie sound tracks included)?
>
> ME!
>
> I do. I did!
For me, "full bandwidth" means flat and powerful to 20 Hz, and
not to a wimpy 40 Hz. How about that one?
After all, we are talking about stereo LOW bass. I have that kind
of extension on my center channel (Hsu TN1220), plus my main sub
(a Velodyne F1800RII, which deals with the L/R mains, plus the
surrounds) also is flat to 20 Hz.
My four surrounds themselves are refurbished Allison Model Four
systems (these were in production when most RAO posters were
still playing stickball), and they are easily flat to 50 Hz,
although I cut them off at 90 Hz and send their bass to the
Velodyne. Unfortunately, the nature of my surround processor
makes it impossible for me to switch the surrounds from a sub to
full-bandwidth on the fly.
In any case, if stereo bass is viable, I ought to hear the
artifact with recorded music that has almost certainly has stereo
bass (early Telarc, many Delos, most Gothic, and Decca Tree
recorded London releases), when I switch from the mono sub to the
full-bandwidth (well, flat to 30 Hz in my room) Allison IC-20
models.
I can do that switching on the fly, and I don't detect any
low-bass stereo artifacts coming or going during the switchovers.
Howard Ferstler
bfeng
Howard Ferstler wrote:
> "Dr. B. J. Feng" wrote
> > Howard Ferstler wrote:
> > > Of course, the dual woofers will still add coherently down really low,
> >
> > Evidence that you still don't understand what we're talking about.
> > If there is incoherent stereo bass info in the program material,
> > those woofers do not add coherently
> > John
>
> Even a recording with stereo bass will have some mono-bass
> artifacts, and those will add coherently.
Great, so mono-bass is justified as a means of reducing spkr
and room interaction some of the time. To say that this occasional
benefit justifies throwing out the interchannel phase information that
was present in the original venue/recording is ... stupid. Better
to have a LF summation switch (with adjustable LP/HP frequency)
in your preamp. That way, you can switch to mono-bass when
it suits you, and you can reproduce the LF phase info if you
like. So why don't all good preamps have one of these switches?
Because preamp functionality is still somewhat driven by traditions
founded in the LP (we must use summed bass channels) era.
Can you make the next step of logic, or is more hand holding necessary?
John F.
bfeng
The response anomalies that Howard is referring to (if
Iunderstand him) are spatially static phenomena in
practical application, no? Stereo subs produce significantly
higher (magnitude) peaks and nulls than an ideally placed
mono sub. Unless these anomalies are directly at the
primarly listening position, is it really that bad?
As far as beign able to record it (sure) but not convey it in
the "best manner" to the listener, that's a judgement call.
One listener might be able to work around a couple of
peaks and nulls by varying placement of couch, and then
enjoy what perceivable information there is in the phase of
the sub 80Hz signals. Another might might not be so lucky.
John
bfeng
Howard Ferstler wrote:
> they are easily flat to 50 Hz,
> although I cut them off at 90 Hz and send their bass to the
> Velodyne. Unfortunately, the nature of my surround processor
> makes it impossible for me to switch the surrounds from a sub to
> full-bandwidth on the fly.
which is precisely why I said you do NOT have the facilities to do a comparions
test of the effect that JJ presented to rao.
John
bfeng
end of your posts, be they in agreement with
my opinions or not.
John
J. Lane
> Those impact frequency response, not spatiality. However, in
> some cases the difference might be interpreted wrongly.
> Certainly, the soundfield will be different.
So suckouts are not cancellation nulls, right Howard? Were they
recorded at the mixing equalizer that way then? But if they're
not cancellation nulls, then they're not phase-related, right?
And hence, not being phase-related, they have no effect on
preceived placement? Am I following this?
So how then can the "soundfield be different"?
Hob...@in.gum.tree
>It's always a pleasure to be on the receiving
>end of your posts, be they in agreement with
>my opinions or not.
>
>John
>
Not always, I hope.
BTW I've found the cause of all RAO's problems - Chef's Knob.
http://x66.deja.com/[ST_rn=ap]/getdoc.xp?AN=665752739&CONTEXT=968403468.1650655293&hitnum=6
"Happiness is an air chisel"
Arny Krueger
"bfeng" <bf...@attglobal.net> wrote in message
news:39B8679B...@attglobal.net...
>
>
> Howard Ferstler wrote:
>
> > "Dr. B. J. Feng" wrote
> > > Howard Ferstler wrote:
> > > > Of course, the dual woofers will still add coherently down
really low,
> > > Evidence that you still don't understand what we're talking
about.
> > > If there is incoherent stereo bass info in the program
material,
> > > those woofers do not add coherently
> > Even a recording with stereo bass will have some mono-bass
> > artifacts, and those will add coherently.
I think we may have to give up on the idea that the subwoofers add at
all. I keep saying "run one woofer at a time".
At this point I think the minimal multichannel subwoofer
configuration would be 3 units: Left, Right, and Center. I think the
left and right subs might naturally end up being positioned in
positions that are as extreme as immediately to the left and right of
the listener. I think the center sub would be centered in front of
the listener. There may also be an argument for a truely centered sub
that is located at "the sweet spot", right under or above the
listener(s).
It seems clear to me that recording procedures will have to be
altered to exploit this. For example one common arrangeent of
lowest-rank organ pipes is that the pipes in the lowest octave(s) are
on either side of the room, with adjacent notes on opposite sides.
Let me suggest that perhaps the *right* way to set up the microphones
for the sub-bass would be to put a microphone very close to each set
of pipes so that the mic picks up primarily that set of pipes. This
would minimize interferance effects even though both the Left and
Right subs were active at the same time. They would be playing
uncorrelated signals.
> Great, so mono-bass is justified as a means of reducing spkr
> and room interaction some of the time. To say that this occasional
> benefit justifies throwing out the interchannel phase information
that
> was present in the original venue/recording is ... stupid.
Only if we find that multichannel subs actually sound *better*. I see
a great potential for that, but I'm not willing to say I know the
final answer until I hear the whole thing *work*.
> Better
> to have a LF summation switch (with adjustable LP/HP frequency)
> in your preamp. That way, you can switch to mono-bass when
> it suits you, and you can reproduce the LF phase info if you
> like.
I think that in the final analysis, the best way to handle program
material with mono bass is to reproduce it through the center sub.
> So why don't all good preamps have one of these switches?
It's a new requirement.
> Because preamp functionality is still somewhat driven by traditions
> founded in the LP (we must use summed bass channels) era.
Exacty.
> (Mr. Ferstler) Can you make the next step of logic, or is more hand
holding necessary?
...don't hold your breath...
IME getting Ferstler to expand his limiting thinking on the topic of
multichannel is just as "easy" as getting some other people to expand
their limited thinking about preference. When somebody thinks they
know better than you, its pretty hopeless.
Howard Ferstler
>
> Tom,
>
> The response anomalies that Howard is referring to (if
> Iunderstand him) are spatially static phenomena in
> practical application, no? Stereo subs produce significantly
> higher (magnitude) peaks and nulls than an ideally placed
> mono sub. Unless these anomalies are directly at the
> primarly listening position, is it really that bad?
Suckout cancellations in the bass range are power-response
related and influence the entire sound field. They have
nothing to do with standing waves, but involve out-of-phase
signals from one woofer getting to another at just the right
time to cancel its power output. The canceled woofer is
doing the same thing to the other woofer. So, you get a dip
in power response. If any large room boundaries are at
distances that are half those found between the woofer
centers, the problem is amplified. Hence, a pair of woofers
at 12 feet apart and with each being 6 feet from a front
wall, side wall or ceiling, will have a substantial dip at
about 56 Hz. Using a single sub, located in the corner, and
crossed over at 80-90 Hz will eliminate this artifact. Using
two subs will bring it back to life.
While a standing-wave artifact might accidentally cancel out
a power-response suckout anomaly at some listening
positions, the fact is that spaced woofer systems still have
the potential to create Allison Effect style cancellations
throughout the room.
Also, the coherent reinforcement with any mono-bass part of
the signal at really low frequencies also impact the overall
power input to the room, and not just at specific locations.
> As far as beign able to record it (sure) but not convey it in
> the "best manner" to the listener, that's a judgement call.
> One listener might be able to work around a couple of
> peaks and nulls by varying placement of couch,
As I have noted, these peaks and nulls are related to the
bass-power *input* to the room, and not to standing wave
peaks or nulls. The phenomenon is related to what we get
with the Allison Effect at mid-bass frequencies, but at
lower frequencies more distant boundaries and multiple
woofers at substantial distances from each other will
deliver the same effect.
> and then
> enjoy what perceivable information there is in the phase of
> the sub 80Hz signals. Another might might not be so lucky.
Sorting those signals out so as to be able to determine
whether they are significant when compared to the very
substantial amount of hall-ambiance information at higher
frequencies and coming from the spaced satellites is harder
than some people think.
Howard Ferstler
Howard Ferstler
>
> Howard Ferstler wrote:
> > Even a recording with stereo bass will have some mono-bass
> > artifacts, and those will add coherently.
> Great, so mono-bass is justified as a means of reducing spkr
> and room interaction some of the time. To say that this occasional
> benefit justifies throwing out the interchannel phase information that
> was present in the original venue/recording is ... stupid.
Hey, I am still awaiting some information on any currently
available recordings that demonstrate this artifact. As I
noted, I have reviewed a number of Telarc, Delos, London,
and Gothic recordings that use spaced microphone techniques,
and I cannot hear any low-bass stereo artifacts.
You keep talking about this phenomenon as if it is something
that can actually be recorded. OK, how about some examples.
After all, you claim to have heard it, and so you ought to
be able to give me the names of some RECORDINGS that you
have listened to that demonstrate the phenomenon. Where are
the names of the recordings you have listened to that prove
your point?
> Better
> to have a LF summation switch (with adjustable LP/HP frequency)
> in your preamp. That way, you can switch to mono-bass when
> it suits you, and you can reproduce the LF phase info if you
> like.
Hey, this is a great idea. It will serve the same placebo
function as a phase-reversal switch.
> So why don't all good preamps have one of these switches?
> Because preamp functionality is still somewhat driven by traditions
> founded in the LP (we must use summed bass channels) era.
Well, maybe nobody can hear it and they wanted to keep from
making the preamp more complex and costly than necessary.
You claim to be able to hear the effect with music, and I
simply need to know the names of the recordings you listened
to that highlighted the phenomenon. Names, names, names. I
need recording names.
> Can you make the next step of logic, or is more hand holding necessary?
No. What is necessary are the names of recordings you have
listened to that prove your point.
Howard Ferstler
Howard Ferstler
>
> "Nousaine" <nous...@aol.com> wrote in message
> news:20000907172425...@ng-ch1.aol.com...
>
> > >> Well, have JJ (or Arny, or you) offer up some titles that
> > >> proves his (and your) point with musical program material.
>
> > Need those myself.
Me, too. I am eager to hear this commercially produced
recordings that have audible stereo low bass. Low for me
would mean below the usual 80- or 90-Hz subwoofer crossover
point.
> I'm not sure that anybody knows how to make them will talk or release
> something that will let the cat out of the bag.
>
> I think that the comment: "Well, we've had spaced microphone
> recordings for a long time", miss the point.
>
> Recording practice has suffered for a long time from the idea that we
> could somehow position microphones in a room on say, some kind of
> regular grid, and then play what those microphones pick up through
> (omnidirectional?) speakers on the same grid and have some kind of
> realism.
>
> Multichannel bass might be the situation where the fallacy of this
> approach becomes most obvious.
>
> If I were going to make a multichannel bass recording, I would
> remember that my goal is not to record the sound field at a certain
> point in the room where the live performance happens, but rather to
> play back something that will stimulate that sound field at the
> corresponding point in the listening room. I think that particularly
> with sub-bass the degree to which these two things are vastly
> differnet becomes most clear.
Well, if as you indicate the companies who produce the
spaced-omni (mostly classical) recordings I noted are not
really giving us "stereo bass," just what kind of wild and
weird microphone placement will recording engineers have to
employ in order to record this so-called, "realistic" stereo
bass?
Basically, you are saying that no normal, spaced-microphone
recording technique will give us stereo bass down really
low. Consequently all your theories about how this will work
with any possible commercial recordings have to be
substantiated by means of test tones (and headphone
listening). The upshot is that nobody will be able to easily
produce these bass-realistic (or, rather,
LOW-bass-realistic) recordings without resorting to some
very unusual post-production procedures. Procedures that
apparently nobody in the mainstream recording business has
pulled off to your satisfaction at this time.
Howard Ferstler
Howard Ferstler
> At this point I think the minimal multichannel subwoofer
> configuration would be 3 units: Left, Right, and Center. I think the
> left and right subs might naturally end up being positioned in
> positions that are as extreme as immediately to the left and right of
> the listener. I think the center sub would be centered in front of
> the listener. There may also be an argument for a truely centered sub
> that is located at "the sweet spot", right under or above the
> listener(s).
How is this supposed to generate "realistic" low bass? It
looks like you are setting up subs in such a way that they
will generate all sorts of suckout interactions and phase
anomalies that may embellish the sound. However, are we
really reproducing the "stereo" low bass or just creating
some kind of pleasant, possibly not really realistic-at-all,
effect?
> It seems clear to me that recording procedures will have to be
> altered to exploit this. For example one common arrangeent of
> lowest-rank organ pipes is that the pipes in the lowest octave(s) are
> on either side of the room, with adjacent notes on opposite sides.
> Let me suggest that perhaps the *right* way to set up the microphones
> for the sub-bass would be to put a microphone very close to each set
> of pipes so that the mic picks up primarily that set of pipes.
Well, right off we are having to diddle quite a bit to get a
"realistic" sound in the low bass. So much for purist
recording techniques. Recording engineers must be really
enthusiastic about your interesting ideas.
> This
> would minimize interferance effects even though both the Left and
> Right subs were active at the same time. They would be playing
> uncorrelated signals.
You are going to bend the signals as far as possible to get
that square peg into that round hole. I can just see the
current crop of purist-oriented recording engineers jumping
at the chance to create these rather weirdly configured
transcriptions you envision.
> > Great, so mono-bass is justified as a means of reducing spkr
> > and room interaction some of the time. To say that this occasional
> > benefit justifies throwing out the interchannel phase information
> that
> > was present in the original venue/recording is ... stupid.
> Only if we find that multichannel subs actually sound *better*.
In this case, the best we can say is that they sound
different. In some rooms, with some recordings, this might
mean that they sound "better." However, better will probably
involve things other than stereo low bass.
> I think that in the final analysis, the best way to handle program
> material with mono bass is to reproduce it through the center sub.
Well, I do that most of the time, because I use a mode with
my Yamaha processor called Classical/Opera, which steers
in-phase signals to the center. This includes in-phase bass.
However, all the other bass is sent to the main sub. When I
do my stereo vs mono bass comparisons, I shut down the
center and surrounds and just compare the spaced full-range
mains with the sub + mains.
> > (Mr. Ferstler) Can you make the next step of logic, or is more hand
> holding necessary?
>
> ...don't hold your breath...
Hey, am I being inactive, here? I have repeatedly told you
that I cannot hear the phenomenon with a variety of existing
program material. I have also repeatedly asked you guys for
examples of recordings that prove your points.
You keep talking test signals and headphones, but that does
not prove a thing when it comes to determining if what you
say is true in the real world of musical recordings. You
*assume* that it works, because it works with test signals.
However, you cannot *know* if it works unless you come up
with some recordings that proves what you say works with
music.
Since you seem so sure of yourselves in this area, I assume
that you have heard it at work with real recordings, and so
all I need are the names of those recordings. Names, names,
names. I need names.
> IME getting Ferstler to expand his limiting thinking on the topic of
> multichannel is just as "easy" as getting some other people to expand
> their limited thinking about preference. When somebody thinks they
> know better than you, its pretty hopeless.
Hey, if you *know* that stereo bass works with music, this
means that you have heard it with music. So, all I need are
the names of the recordings you used. Well, what are the
names?
Howard Ferstler
Howard Ferstler
Hey, I can at least compare my two mains to my sub + mains.
The mains are flat to 30 Hz in the room.
Incidentally, you keep claiming that the phenomenon is
audible with test signals. However, just *how* do you know
that it will be audible with music? Have you heard it with
music? If so, how about supplying the names of the
recordings you have listened to. Names, names, names. I want
you to prove to me that you have heard the phenomenon of
stereo low bass yourself with musical program material.
Names, names, names. I want to know what recordings you have
used to prove to yourself that this stereo low bass thing is
important.
Howard Ferstler
Howard Ferstler
>
> > > What, no suck-outs?
> > Those impact frequency response, not spatiality. However, in
> > some cases the difference might be interpreted wrongly.
> > Certainly, the soundfield will be different.
> So suckouts are not cancellation nulls, right Howard? Were they
> recorded at the mixing equalizer that way then?
Inter-woofer suckouts are related to the Allison Effect.
They happen when rarefactions in a wave or the compression
part of the same wave produced by a distant woofer
reproducing identical bass signals gets to the other woofer
just in time for the rarefactions and compression peaks to
cancel out the compression and rarefaction parts of the
other woofer's wave. Each woofer does that to the other and
the frequency where it happens will depend upon the spacing
between the woofer centers. At some distance, one woofer
will cancel out identical bass signals being produced by the
other woofer, provided they are producing identical bass
signals. The cancellation is not huge, but it would be huge
if room boundary cancellations (not related to standing
waves, please note) augment the effect.
It is a power-response phenomenon and impacts the bass
signals that are being *input* to the room. You get the same
problems with large boundaries that are half the distance
from the woofer centers you have between the spaced woofer
centers. The effect has nothing to do with standing waves or
what was recorded.
> But if they're
> not cancellation nulls, then they're not phase-related, right?
They are cancellation nulls that effect power-response
uniformity and the direct-field signals together. The
canceled woofers are out of phase with each other at some
distance-related frequency.
> And hence, not being phase-related, they have no effect on
> preceived placement? Am I following this?
Placement will impact those quarter-wavelength
cancellations. It is a double-barreled phenomenon, involving
the two, spaced woofer systems and the location of each
woofer system in relation to large room boundaries.
> So how then can the "soundfield be different"?
The frequency response changes, due to the cancellation
suckouts.
Howard Ferstler
J. Lane
they
> > recorded at the mixing equalizer that way then?
>
> Inter-woofer suckouts are related to the Allison Effect.
> They happen when rarefactions in a wave or the compression
> part of the same wave produced by a distant woofer
> reproducing identical bass signals gets to the other woofer
> just in time for the rarefactions and compression peaks to
> cancel out the compression and rarefaction parts of the
> other woofer's wave. Each woofer does that to the other and
> the frequency where it happens will depend upon the spacing
> between the woofer centers. At some distance, one woofer
> will cancel out identical bass signals being produced by the
> other woofer, provided they are producing identical bass
> signals. The cancellation is not huge, but it would be huge
> if room boundary cancellations (not related to standing
> waves, please note) augment the effect.
While I've never studied Alison, the effect you describe is
possible only when the woofers are either out of phase
completely, or, if they are correctly in phase, are so far apart
and so aysmmetrically placed as to make this possible at the
frequencies typically handled by subs. A wavelength at 80Hz is
14 feet or so; at 40Hz, nearly 30 feet. Unless the original
recording has a complete or partial significant cancellation
related to these wavelengths or even longer ones, I don't see how
your woofers, at normal distances of say, 10 feet between the
speakers, 12 feet to the listener, can triangulate significant
cancellation loss at your (more or less) center position. This
being the case, I'm further unaware of low-frequency stereo
microphones in live events being placed 15-30 feet apart or
asymmetrically skewed unless the desired effect is corrupt the
stereo perspective. Perhaps someone can enlighten me. Even if
this were so, than the normal placement of a pair of fullrange
stereo speakers will merely reproduce the recording error leaving
the listener with a distinct sense that this is one label to
leave on the shelf next time.
The notion that a pair of fullrange speakers at normal placement
in a home stereo is fatally flawed by low frequency phase-related
cancellation is incorrect. And if the room is so overwhelmingly
influential in this regard, well, you know what to work on.
Intentionally throwing away usable information, however slight it
may be due to the uniformity of the two channels at these
frequencies, because the room is flawed seems counterproductive.
> > But if they're
> > not cancellation nulls, then they're not phase-related,
right?
>
> They are cancellation nulls that effect power-response
> uniformity and the direct-field signals together. The
> canceled woofers are out of phase with each other at some
> distance-related frequency.
So they ARE phase-related?
> Placement will impact those quarter-wavelength
> cancellations. It is a double-barreled phenomenon, involving
> the two, spaced woofer systems and the location of each
> woofer system in relation to large room boundaries.
Actually, I had said "perceived placement" referring to the
perception of image (soundstage) skew from phase-related effects.
And it seems to me that these cancellations will indeed affect
perceived placement within the soundstage.
> > So how then can the "soundfield be different"?
> The frequency response changes, due to the cancellation
> suckouts.
Uniform frequency response alterations across both channels
affects front to rear placement, assuming that's what you're
trying to say. Phase-related effects related to differences in
position of the speakers that is not uniformly amplitude
dependent in both channels affects side to side, or image
placement. it seems your description can use some clarification.
Steve Zipser
"Howard Ferstler" <hfer...@mailer.fsu.edu> wrote
> Inter-woofer suckouts are related to the Allison Effect.
IS this where the white rabbit blows the mad hatter?
Allison Wonderland indeed.
Hob...@in.gum.tree
<hfer...@mailer.fsu.edu> wrote:
>Suckout cancellations in the bass range are power-response
>related and influence the entire sound field. They have
>nothing to do with standing waves, but involve out-of-phase
>signals from one woofer getting to another at just the right
>time to cancel its power output.
Bollocks!
Howard Ferstler
It is not just at the listener position. The Allison Effect
mainly deals with suckout in the midbass. Reflections from
nearby boundaries will, at some frequencies (which
frequencies will depend on the distances involved), arrive
back at the woofer so that the rarefaction and compression
parts of the reflected wave are out of phase with the signal
being generated by the woofer. The result is a
quarter-wavelength suckout that effects both the direct
signal and the reverberant signal *input* to the room.
Listening position has nothing to do with it. The actual
power output of the woofer system is altered.
In the same way, more distant boundaries will do the same
thing at lower frequencies. And, spaced-woofer systems will
do the same thing as what would happen if a boundary were
placed midway between those woofers. The rarefactions and
compressions part of one woofer's signal will arrive at the
other woofer out of step with what that other woofer
generates. The result is a null at a frequency that will
depend upon the distances involved. At higher frequencies,
these boundary nulls are so choppy and influenced by other
variables that they are not significant, but at lower
frequencies than can impact the frequency response input of
a system to a room.
> This
> being the case, I'm further unaware of low-frequency stereo
> microphones in live events being placed 15-30 feet apart or
> asymmetrically skewed unless the desired effect is corrupt the
> stereo perspective. Perhaps someone can enlighten me. Even if
> this were so, than the normal placement of a pair of fullrange
> stereo speakers will merely reproduce the recording error leaving
> the listener with a distinct sense that this is one label to
> leave on the shelf next time.
The suckout is independent of the program material. As long
as both woofers are generating some coherent bass signals,
the inter-woofer effect will be there. And it does not
matter whether the bass signals are coherent or not when it
comes to boundary interactions with either woofer.
> The notion that a pair of fullrange speakers at normal placement
> in a home stereo is fatally flawed by low frequency phase-related
> cancellation is incorrect.
Well, then Allison is wrong, and the Allison Effect does not
exist at higher, mid-bass frequencies, either. I will note
that at bass frequencies we get a multitude of other
variables that may overshadow the suckout phenomenon, but
the fact remains that it can and often will produce audible
glitches in the bass response uniformity.
Opting to use a subwoofer, placed in a corner and crossed
over so that potential suckouts from the satellites are
below that crossover frequency and potential suckouts from
the mono sub are above that crossover frequency, will solve
that part of the response-linearity problem in the bass.
> And if the room is so overwhelmingly
> influential in this regard, well, you know what to work on.
Woofer placement and mild amounts of equalization.
> > > But if they're
> > > not cancellation nulls, then they're not phase-related,
> right?
> > They are cancellation nulls that effect power-response
> > uniformity and the direct-field signals together. The
> > canceled woofers are out of phase with each other at some
> > distance-related frequency.
> So they ARE phase-related?
Distances will determine at what point signals from woofers
going to other woofers or from a woofer to a boundary or
boundaries and then reflected back to the same woofer in
time for the reflected and direct wavelengths to be out of
phase with each other, yes, they are phase related. At some
frequency, spaced woofer systems will generate signals that
are out of phase with each other. What frequency will depend
upon the distances between the woofers.
> > Placement will impact those quarter-wavelength
> > cancellations. It is a double-barreled phenomenon, involving
> > the two, spaced woofer systems and the location of each
> > woofer system in relation to large room boundaries.
> Actually, I had said "perceived placement" referring to the
> perception of image (soundstage) skew from phase-related effects.
> And it seems to me that these cancellations will indeed affect
> perceived placement within the soundstage.
Well, insofar as the speakers will not be generating flat
response in the bass this might be possible. However, I do
not consider this to be an important byproduct of the
phenomenon.
> > > So how then can the "soundfield be different"?
> > The frequency response changes, due to the cancellation
> > suckouts.
> Uniform frequency response alterations across both channels
> affects front to rear placement, assuming that's what you're
> trying to say.
No. Since frequency response is part and parcel of a
system's soundfield, that soundfield will be changed by any
frequency-response aberrations, including those in the bass.
To my knowledge, the inter-woofer cancellations cannot
impact soundstaging. However, if stereo speaker systems are
each placed at different distances from boundaries, such
that their mid-bass outputs would be different, then
soundstaging will be effected.
Howard Ferstler
Nousaine
>Tom,
>
>The response anomalies that Howard is referring to (if
>Iunderstand him) are spatially static phenomena in
>practical application, no? Stereo subs produce significantly
>higher (magnitude) peaks and nulls than an ideally placed
>mono sub. Unless these anomalies are directly at the
>primarly listening position, is it really that bad?
Well I have three primary listening positions. But I'm referring to modal
activity. What happens with non-corner subwoofers is that some modes are NOT
excited causing holes in the response. So even at the primary listening
position we get less even in-room frequency response.
>As far as beign able to record it (sure) but not convey it in
>the "best manner" to the listener, that's a judgement call.
>One listener might be able to work around a couple of
>peaks and nulls by varying placement of couch, and then
>enjoy what perceivable information there is in the phase of
>the sub 80Hz signals. Another might might not be so lucky.
>
>John
In my experience the single most important factor in realistic playback
(assuming that loudness is adequate) is evenness of frequency response. If we
sacrifice that. I'm not sure retaining phase integrity will improve things? Of
course multiple subwoofers could all be corner placed BUT I've yet to see a
room where all corners are really useful.
As I said, I'm all for advancement of the art but I don't see this important
aspect being considered here.
J. Lane
> > At this point I think the minimal multichannel subwoofer
> > configuration would be 3 units: Left, Right, and Center. I
think the
> > left and right subs might naturally end up being positioned
in
> > positions that are as extreme as immediately to the left and
right of
> > the listener. I think the center sub would be centered in
front of
> > the listener. There may also be an argument for a truely
centered sub
> > that is located at "the sweet spot", right under or above the
> > listener(s).
Fester replied:
> How is this supposed to generate "realistic" low bass? It
> looks like you are setting up subs in such a way that they
> will generate all sorts of suckout interactions and phase
> anomalies that may embellish the sound. However, are we
> really reproducing the "stereo" low bass or just creating
> some kind of pleasant, possibly not really realistic-at-all,
> effect?
"All sorts"? Sorry, Howard, I'm actually with Arn on this one.
Unless you tell us how big ole long wavelengths cancel from a
pair of bass sources placed roughly equidistant to the listener
in an average setting, this cancellation chatter is just hokum.
Why don't your Dunlavy midranges comb? Because they're close
enough together within the frequency spectrum they cover to act
as a single source...
J. Lane
> mainly deals with suckout in the midbass. Reflections from
> nearby boundaries will, at some frequencies (which
> frequencies will depend on the distances involved), arrive
> back at the woofer so that the rarefaction and compression
> parts of the reflected wave are out of phase with the signal
> being generated by the woofer. The result is a
> quarter-wavelength suckout that effects both the direct
> signal and the reverberant signal *input* to the room.
> Listening position has nothing to do with it. The actual
> power output of the woofer system is altered.
Don't you mean to say that the power response in the room is
altered? The power output by the woofers is close to reference,
assuming reasonable damping by the amplifier; it's the room
energy that varies. And speaker pairs, now that you're referring
to power and not spl, average the nonlinearities you're concerned
with, assuming placement has been optimized to do so. But of
course, you've shifted the topic from your previous claim that
woofer pairs comb by virtue of the fact that the two of them
merely go out of phase with one another referenced to the
listener, haven't you?
Power response averaged over the time it takes to fully involve
the room at any given frequency would tend to swamp line-of-sight
'reflections" in any given direction, wouldn't they? But, as I
understand it, the cancellations you refer to must be mostly the
work of two woofers summing presumably along the axis of greatest
phase difference between them, or on a line drawn directly
through them both, or, assuming conventional placement,
perpendicular to the listening axis between listener and center
stage. This being the case, I'm stuck visualizing these
cancellations as distinctly part of the spl response to the far
left and far right of the listener. On the other hand, the power
response you're now referring to, to come full circle, averages
these spl cancellations to a large degree. Correct?
> And, spaced-woofer systems will
> do the same thing as what would happen if a boundary were
> placed midway between those woofers. The rarefactions and
> compressions part of one woofer's signal will arrive at the
> other woofer out of step with what that other woofer
> generates. The result is a null at a frequency that will
> depend upon the distances involved. At higher frequencies,
> these boundary nulls are so choppy and influenced by other
> variables that they are not significant, but at lower
> frequencies than can impact the frequency response input of
> a system to a room.
Howard, assuming a normal placement of 10 feet between speakers,
and an average size room, and further assuming that the woofers
are dominated by the power response at these omnidirectional
wavelengths, not the on-axis spl in any direction, how exactly is
it that these devices can suddenly go so completely out of phase
as to influence the response when they're making wavelengths a
number of times longer than the distance between them?
Especially if the listener is as far from one as from the other
which is the case with two fullrange speakers.
> The suckout is independent of the program material. As long
> as both woofers are generating some coherent bass signals,
> the inter-woofer effect will be there. And it does not
> matter whether the bass signals are coherent or not when it
> comes to boundary interactions with either woofer.
Sorry, don't follow. Any channel-relative phase shifting in the
mix at a given frequency shows up at the woofers where, if it is
severe enough, actually will cancel to degrees varied by the
amount of phase difference. Conversely, if the mix is recorded
at mono potential in both channels, the cancellations you're
referring to do not occur due to the distances between woofers
and listener in average situations.
> > The notion that a pair of fullrange speakers at normal
placement
> > in a home stereo are fatally flawed by low frequency
phase-related
> > cancellation is incorrect.
> Well, then Allison is wrong, and the Allison Effect does not
> exist at higher, mid-bass frequencies, either. I will note
> that at bass frequencies we get a multitude of other
> variables that may overshadow the suckout phenomenon, but
> the fact remains that it can and often will produce audible
> glitches in the bass response uniformity.
I doubt Allison found a way for two woofers operated within a
half-wavelength or less of one another driven with material of
reasonable phase integrity to suffer cancellations for the reason
I thought you originally cited. Am I wrong? If so, how do two
sources comb under these circumstances unless the placement is so
bad and the room so reverberant as to overwhelm the system with
far-field, reverberant problems? Perhaps if you calculate an
environment specifically in order to cancel and then put one
woofer 10 feet further from you than the other, you will have a
cancellation situation bad enough to blame a two-woofer system.
But with a logically designed room and equidistant woofers, the
room's response itself should dominate. And Howard, I recall
this thread being about stereo _sub_woofers and I thought I
recalled your mention of sub-80Hz info. At the least, I pointed
out the wavelengths below 80Hz myself...
> Distances will determine at what point signals from woofers
> going to other woofers or from a woofer to a boundary or
> boundaries and then reflected back to the same woofer in
> time for the reflected and direct wavelengths to be out of
> phase with each other, yes, they are phase related. At some
> frequency, spaced woofer systems will generate signals that
> are out of phase with each other. What frequency will depend
> upon the distances between the woofers.
I hear your assertion but can't see the mechanism given the
environment, wavelengths, and placements in question based solely
on the fact that two systems are present. OTOH, room issues
themselves are an almost entirely different area...
Hob...@in.gum.tree
<nos...@farmerinthedell.com> wrote:
snip.
>this cancellation chatter is just hokum.
I think you have more or less got the idea.
If you compare the area of the driver cone, say 1ft diameter to the
area of the surface of a sphere, say 10ft in diameter ( 'free field'
conditions) or compare the volume of the sub enclosure to the volume
of the room ( 'pressure pot' conditions) you get a rough idea of the
amount the motion of one sub can effect the displacement or efficiency
of the other. The answer is "not a lot". If you take account of the
low efficiency of subs or the fact that they may be servo controlled
the answer may be "bugger all". This is not the same as zero, note.
Howard Ferstler
As a line.
Howard Ferstler
J. Lane
> > "All sorts"? Sorry, Howard, I'm actually with Arn on this
one.
> > Unless you tell us how big ole long wavelengths cancel from a
> > pair of bass sources placed roughly equidistant to the
listener
> > in an average setting, this cancellation chatter is just
hokum.
> > Why don't your Dunlavy midranges comb? Because they're close
> > enough together within the frequency spectrum they cover to
act
> > as a single source...
Howard, presumably at a loss for words, explained:
> As a line.
The Dunlavy mids are crossed high enough to become directional at
the very top of their bandwidth?
Howard Ferstler
> Don't you mean to say that the power response in the room is
> altered? The power output by the woofers is close to reference,
> assuming reasonable damping by the amplifier; it's the room
> energy that varies...
Allison published several articles on this topic in the JAES a
number of years ago. (I can give you the exact issue numbers, if
you want.) Rather than try to pull data from them, I will excerpt
from one of his early explanatory brochures and then show how it
can be expanded upon to include spaced woofer/woofer
interactions.
Roy Allison on the Allison Effect:
Consider a typical box loudspeaker system positioned in a room so
that its woofer cone is about two feet from a large room
boundary. When the speaker is radiating a very low frequency the
cone moves relative slowly and over a relatively long distance.
If the radiated frequency is 40 Hz, for example, it takes 1/40
second (25 ms) for the cone to execute one complete forward and
backward cycle. Each half of the cycle takes 12.5 ms.
As the cone begins a forward movement it generates the start of a
compression wave. This impulse travels as the speed of sound to
the boundary and is reflected back toward the woofer cone,
arriving there some 3.5 ms after it left, while the woofer is
still generating the compression half of the sound cycle. The
reflected wave increases the instantaneous pressure seen by the
woofer and enables it to radiate more power than it could in free
space. The reflected pressure is in phase coincidence with the
woofer's motion.
But as the woofer tries to radiate higher frequencies, it must
reverse its motion more quickly. At 140 Hz, for example, the cone
reverses direction every 3.5 ms. It begins its inward half-cycle
of motion (attempting to create a rarefaction) just as the
compression-wave reflections begin to arrive back from the room
boundary two feet away. In this case the reflected pressure is
completely out of phase with the cone motion, decreasing its
radiation efficiency.
End of quote.
OK, obviously, if you have more than one boundary at identical
distances from the woofer centers, this problem will be made even
worse. In addition, if you have a second woofer at double the
distance (which in effect is the same as having a boundary half
way between those woofers), it will create the same effect.
If you add in boundaries that are at half the distance, you get
into even bigger trouble. For example, if you had speakers
positioned so that their woofer centers were 12 feet apart and
those centers were also 6 feet from the side and/or front walls,
you would have a rather pronounced dip at 56.5 Hz.
And, if you move the boundaries or woofers further away, the
suckout notch will work its way down into the lower frequencies.
Distances such as this are typical with stereo woofer spacing,
and are also not uncommon in situations where speakers are pulled
out some distance from room boundaries.
There is a formula for calculating the location of the suckout
null: 1130/d X .3.
The "d" is the distance from a woofer center to the boundary in
feet (you would use one half the distance between woofer centers
for "d" when dealing with that aspect of the phenomenon). The
actual proper multiplier should be .25, rather than .3. However,
that would only work if the boundary were equidistant from the
woofer center over its entire surface. Because it is usually
flat, Allison discovered that .3 worked more accurately. The
1130, by the way, is the speed of sound at sea level. You would
use a different number at higher altitudes.
Note that with speakers about 12 feet apart the dip would be at
about 56 Hz, as I previously noted. If they were about 10 feet
apart, it would be at 67 Hz. If room boundaries were at half
those distances, the effect would be worsened at those
frequencies. OK, insert a big subwoofer into one of the front
corners and set its crossover (HP and LP) at 80 Hz. In this case,
the dips at 56 and/or 67 Hz would below the operating range of
the satellites and therefore would not have any effect. The sub
would be so close to the room boundaries in the corner that any
dips it could generate would be well above the 80 Hz crossover
point.
So, placing satellites properly, placing a subwoofer properly,
and then setting the crossover properly, will do away with a lot
of those woofer/woofer and woofer/boundary artifacts. Not all of
them, but at least some of them. Adding in a second subwoofer
will reintroduce the inter-woofer part of the problem.
Howard Ferstler
Howard Ferstler
>
> On Fri, 8 Sep 2000 17:44:43 -0600, "J. Lane"
> <nos...@farmerinthedell.com> wrote:
>
> snip.
> >this cancellation chatter is just hokum.
>
> I think you have more or less got the idea.
>
> If you compare the area of the driver cone, say 1ft diameter to the
> area of the surface of a sphere, say 10ft in diameter ( 'free field'
> conditions) or compare the volume of the sub enclosure to the volume
> of the room ( 'pressure pot' conditions) you get a rough idea of the
> amount the motion of one sub can effect the displacement or efficiency
> of the other. The answer is "not a lot". If you take account of the
> low efficiency of subs or the fact that they may be servo controlled
> the answer may be "bugger all". This is not the same as zero, note.
Yes, once you have pressure-pot conditions, all bets are off.
However, if subs are placed close enough together for the bass to
cancel above the frequency where the room forms a pressure pot,
then the bets are back on again. For example, if the room is
fairly large and the center of the sub drivers are 10 feet apart,
there will be a suckout notch at about 67 Hz. That is probably
going to be a problem, because the room will not be forming a
pressure pot at that frequency. In addition, if the subs are also
each 5 feet from a room boundary, the problem will be made worse.
The solution: place the satellites to that any boundary/woofer or
woofer/woofer related notches are below the point where one will
set the sub crossover point. Then, put the sub in a corner. Any
boundary-related artifacts that it has the potential to generate
will be above the crossover point.
Howard Ferstler
Hob...@in.gum.tree
You have to consider the magnitude of the effect as well as the
frequency. If you consider two, driven subs, a and b, in free space
the total acoustic power from sub (a) remains constant as the
wavefront expands but the power per unit area decreases with radius.
The amount of power that passes through a circle of the area equal to
that of sub (b) (equal to sub (a)) is a small fraction of the total,
given by the ratio of this area to the area of the surface of a sphere
of radius equal to the separation between them. If the two subs are
identical and driven with the same power, this ratio is also the ratio
of the acoustic power generated by sub (b) to the the interfering
power from sub (a). This interfering wave will produce forces acting
on the cone of sub (b) in addition to those of the voice coil which
will change the amount it moves. The affect of the external acoustic
pressure due sub(a)'s movement results in a small force compared to
the internal forces and is related to the subs efficiency. Changes in
the amount of displacement of sub(b) due to external effects caused by
another sub (a). with a fixed (coherent) phase relationship, will
affect the efficiency and the impedance of sub (b) but in the case I
mentioned, the *available* interfering power is of the order of
1/1000th of the total acoustic power producing forces acting on sub
(b) and if the sub effeciency is .1%, most of this available power
will be reflected and diffracted as from a large brick. I can't see
this giving a very big suckout, myself.
J. Lane
quotes Allison:
Your quotation of this easy to understand description of room
boundary effects contains no data on multiple woofers canceling
due to their wavelengths overlapping in a nonlinear way. How do
woofers spaced a typical 10 or 12 feet apart cancel severely
under 80Hz?
The Devil
<bf...@attglobal.net> wrote:
>Dear RAO Freaks,
>
>I've been away "doing the work" so I'm really late to this
>thread. Saw Arnyk's post about generating the signal.
>Arny -- it's NOT a fixed offset but a phase modulation
>that JJ is talking about.
>
>I've generated a 10 second .wav file that shows the
>localization effect of a 2hz phase modulation
>(I think it was 0.1 radian peak modulation). If anyone
>wants it, I can email it out. Best if I can email it
>to someone who has a >28.8k connection for further distribution
>(that's all I can get thru my local telco).
>
>
>Dave, etal. With all due respect, there are a few
>points you guys are ignoring:
>
Would you like a handkerchief, Howie?
--
The Devil
Arny Krueger
"J. Lane" <nos...@farmerinthedell.com> wrote in message
news:#9fPiezGAHA.358@cpmsnbbsa07...
> Your quotation of this easy to understand description of room
> boundary effects contains no data on multiple woofers canceling
> due to their wavelengths overlapping in a nonlinear way. How do
> woofers spaced a typical 10 or 12 feet apart cancel severely
> under 80Hz?
The wavelength of 80 Hz is 13.75 feet. That means that in 6.9 feet
an 80 Hz wave experiences 180 degrees (phase reversal) of phase
shift.
OK you have two subwoofers about 7 feet apart. You are sitting on top
of one of them. Your ear receives 80 Hz from the one you are sitting
on with essentially no phase shift. Your ear receives 80 Hz, but 180
degrees out of phase from the other one. If their amplitudes are
similar, they will cancel each other out. Move up to 90 Hz and the
cancellation is far less. Move up to 160 Hz, and the phase shift is
360 degrees, which has the same effect as no phase shift, and the two
signal add. Move up to 240 Hz and we are back at cancellation.
Because of the regular shape of the frequency response
characteristic, we call this a "Comb filter" effect.
Listening rooms are full of these kinds of effects at all audible
frequencies. Please see the right hand column of
http://www.pcabx.com/technical/dips_pips_tips/index.htm for examples
of what comb filtering sounds like when applied to musical program
material.
Hob...@in.gum.tree
wrote:
>OK you have two subwoofers about 7 feet apart. You are sitting on top
>of one of them. Your ear receives 80 Hz from the one you are sitting
>on with essentially no phase shift.
Just where exactly do you keep your ears?
Your ear receives 80 Hz, but 180
>degrees out of phase from the other one. If their amplitudes are
>similar, they will cancel each other out. Move up to 90 Hz and the
>cancellation is far less. Move up to 160 Hz, and the phase shift is
>360 degrees, which has the same effect as no phase shift, and the two
>signal add. Move up to 240 Hz and we are back at cancellation.
>
>Because of the regular shape of the frequency response
>characteristic, we call this a "Comb filter" effect.
>
>Listening rooms are full of these kinds of effects at all audible
>frequencies. Please see the right hand column of
>http://www.pcabx.com/technical/dips_pips_tips/index.htm for examples
>of what comb filtering sounds like when applied to musical program
>material.
>
>
J. Lane
Exactly.
Howard Ferstler
They interact with each other the same way they would each
interact with a large, reflective boundary 6 feet away. The net
effect is identical. Allison has also told me that the formula
for calculating the frequency of the cancellation would be the
same, although you would use a distance "D" in the formula that
was half that between the woofer centers.
At a distance of 12 feet (or 6 feet from a room boundary), you
would get a dip at 56.5 Hz. Using a sub, crossed over at 80 Hz,
puts those satellites out of the range where those cancellations
would take place. Putting the sub in a corner (where its own
cancellations would have to be above 150 Hz), eliminates any
potential problems it might have with interactions above the
80-Hz crossover point. The satellites are not having to deal with
cancellation interference, and neither is the sub.
Howard Ferstler
Howard Ferstler
It does not act on the cone itself. At certain frequencies, the
wave from a more distant woofer will reach that of the other
woofer in such a way that they will be out of phase with it.
(This requires that they be emitting identical bass signals.)
What frequencies will be determined by the distances involved.
This simply impacts the power response, and reduces the power
input to the room by 3 dB. The null dip is only that deep, and
not a complete cancellation, which I assume is the point of your
criticism. Yes, only a small amount of energy is involved in the
cancellation, but it still adds up to 3 dB. Allison published
three different JAES papers on the phenomenon.
However, if the sub or subs (or woofers, if we are talking about
the bass section of a full-range system) are also at a distance
from room boundaries that equal half that between the subs (or
woofers) themselves, the effect will be augmented. So, if the
distance to a boundary is equal to half the distance to the two
subs, the dip will be 6 dB. If an additional boundary is added
in, it will grow to 9 dB. The distances do not have to be exact
for the effect to be cumulative.
The solution is to use a sub/sat system with the crossover set so
that woofer/woofer and boundary/woofer interference notches
generated by the satellites are below the sat/sub crossover
point. The sub should be located so that any boundary/woofer
related notches in its potential response range would be above
the crossover point. No big deal. Adding a second sub simply
reintroduces the problem.
Howard Ferstler
Howard Ferstler
As Dunlavy. I would imagine that they behave as a more coherent
line at the lower part of their range. The trick with such
systems it to make sure that a line of drivers do not have to go
high enough so that the discrete elements begin to behave as
discrete elements.
Howard Ferstler
Howard Ferstler
You need to get out more. I did a whole series of replies to
assorted comments by Mr. Feng and Mr. Krueger on this topic, and
even took time to reply to comments by J. Lane, Middius, and
Zipser. The documentation is there, and I am not in the mood to
repeat it all just for you.
Howard Ferstler
The Devil
<fer...@attglobal.net> wrote:
>> Would you like a handkerchief, Howie?
>You need to get out more. I did a whole series of replies to
>assorted comments by Mr. Feng and Mr. Krueger on this topic, and
>even took time to reply to comments by J. Lane, Middius, and
>Zipser. The documentation is there, and I am not in the mood to
>repeat it all just for you.
Oh my. I guess I should consider myself told and my wrists sharply
blown on.
--
The Devil
Hob...@in.gum.tree
<fer...@attglobal.net> wrote:
Just a quick note,note.
Superposition is the bee's knees but you can't go adding dBs willy
nilly (sp?) unless you want to multiply..
>The solution is to use a sub/sat system with the crossover set so
>that woofer/woofer and boundary/woofer interference notches
>generated by the satellites are below the sat/sub crossover
>point. The sub should be located so that any boundary/woofer
>related notches in its potential response range would be above
>the crossover point. No big deal. Adding a second sub simply
>reintroduces the problem.
>
>Howard Ferstler
Dr. B. J. Feng
Had you read his reply posts, you'd be offering him an
entire box of tissues. But, don't bother as it was just
more of Howard's head-in-the-sand, I-don't-believe-you
drivel.
The Devil wrote:
>
> On Sun, 10 Sep 2000 20:24:19 -0400, Howard Ferstler
> <fer...@attglobal.net> wrote:
>
> >> Would you like a handkerchief, Howie?
>
> >You need to get out more. I did a whole series of replies to
> >assorted comments by Mr. Feng and Mr. Krueger (snip)
>
> Oh my. I guess I should consider myself told and my wrists sharply
> blown on.
>
John Feng
Howard Ferstler
>
> Actually,
>
> Had you read his reply posts, you'd be offering him an
> entire box of tissues. But, don't bother as it was just
> more of Howard's head-in-the-sand, I-don't-believe-you
> drivel.
Whenever I see the term "drivel" used to describe somebody's
opinion, I know was written by an audio tweak, no matter
what kind of title sits in front of his name. It is one of
those favorite words that proto-literate people like to use.
And when I see somebody make a point of putting that title
in front of his name in a newsgroup post, I know we are
seeing somebody who is not exactly sure of his status within
that group, and in need to get a bit of respect from his
readers even before he makes his hopefully intelligent
statement.
Anyway, "Dr." Feng, have you come up with a list of
commercially available recordings that prove your point
about stereo bass when it comes to listening to music
instead of test tones? After all, you claim stereo bass is
audible, but from what I have seen all we have from you in
the way of "evidence" is your extrapolation that says that
if it is audible with test tones it must be audible with
music. This is stretching things a bit, Dr. Feng.
Prove it, Dr. Feng. Otherwise, all your comments dealing
with this particular topic are "drivel." (Pardon my
temporary use of the term "drivel," by the way, but I could
not help myself.)
In addition, explain to us how you separate the
frequency-response related artifacts (coherent reinforcement
down really low and inter-woofer cancellations a bit higher
up in frequency) when you are comparing your mono sub to a
pair of subs. (Headphones do not count, because most people
are using speakers, and headphones will not let the room
insert its two-cents worth.) Tell us how you cull out the
variables so that you can hear the spatiality clues you
claim exist. Also, tell us how you do it with musical
program material, in addition to test tones.
And, again, Dr. Feng, Ph.D., how about a list of musical
recordings that will prove your "theory" about stereo bass
at very low bass frequencies.
Howard Ferstler
George M. Middius
> Whenever I see the term "drivel" used to describe somebody's
> opinion, I know was written by an audio tweak, no matter
> what kind of title sits in front of his name. It is one of
> those favorite words that proto-literate people like to use.
You're not fooling anyone, Clerkie. How about jetting up to NYC
to meet some real hi-fi dealers?
George M. Middius
Howard Ferstler
If I decided to jet up to NYC, the very last thing I would
want to do is "meet some real hi-fi dealers."
Howard Ferstler
viz...@bellatlantic.net
::gack::
Not in my city you don't. No further North than D.C., as far
as I'm concerned ::heh, heh::
Ed
>
>
>George M. Middius
SdW
>>You're not fooling anyone, Clerkie. How about jetting up to NYC
>>to meet some real hi-fi dealers?
> ::gack::
> Not in my city you don't. No further North than D.C., as far
>as I'm concerned ::heh, heh::
Rest assurED...........
Pigs don't fly, Howard doesn't either, and his Mustang
won't last that long.
--
SdW
By now, you should realize I'm posting from a .nl account.
viz...@bellatlantic.net
>viz...@bellatlantic.net said:
>
>>>You're not fooling anyone, Clerkie. How about jetting up to NYC
>>>to meet some real hi-fi dealers?
>
>> ::gack::
>
>> Not in my city you don't. No further North than D.C., as far
>>as I'm concerned ::heh, heh::
>
>Rest assurED...........
>Pigs don't fly, Howard doesn't either, and his Mustang
>won't last that long.
Yeah, wise guy, but there's always the train.
OTOH, AMTRAK usually derails somewhere around South
Carolina...............
::grin::
Ed
Hob...@in.gum.tree
<fer...@attglobal.net> wrote:
>It does not act on the cone itself. At certain frequencies, the
>wave from a more distant woofer will reach that of the other
>woofer in such a way that they will be out of phase with it.
>(This requires that they be emitting identical bass signals.)
>What frequencies will be determined by the distances involved.
>This simply impacts the power response, and reduces the power
>input to the room by 3 dB. The null dip is only that deep, and
>not a complete cancellation, which I assume is the point of your
>criticism. Yes, only a small amount of energy is involved in the
>cancellation, but it still adds up to 3 dB. Allison published
>three different JAES papers on the phenomenon.
>
I have not read the Allison papers but no doubt I could learn
something from them, however, it is more fun to work things out for
yourself from first principles. The free field case is not that
relevant in itself because you dont get to hear the "power response"
but it simplifies things. Let's try another tack. If you want to alter
the power response ( by speaker interaction) you a really talking
about altering the efficiency of the speakers ie. how much power you
get out for a fixed power input. Since I have shown that the linear
displacement (cone excursion) is more or less constant independent of
the second sub and since mechanical work is force times distance, to
double the effeciency we need to double the force due to the outside
air acting on the cone. Force equals pressure times area so we need to
double the pressure excursions. If you put two subs right next to each
other the pressures from each will add if they are in phase. Each will
be twice as efficient (in the limit if you manage to double the
pressur) and if each is fed the same power as a single sub you will
get a total of four times the power of a single sub (6dB) but you are
putting in twice the total power so you have a gain of 3dB compared to
a single sub for the same total power. If you want your -3dB power
response, you have to manage to half the acoustic pressure seen by
each sub by subtracting the pressure due to the second sub or
reflections. In the case I mentioned, the interfering incident power
was 1/1000 of the generated power which gives and additional
squareroot(1/-1000)= -.032 pressure so that the efficiency drops to
(1-.032)/1 a 3% drop or -0.14 dB. ( I might have done this wrong so I
hope someone checks it) If your room was an elipsoid and you placed
one sub at each focus with a n +1/2 wavelength path length (bounced)
you could do a lot better at cancelling (LOTS!) but that seems to be
stretching the typical room a bit. What I really wanted to ask is:
"Where does Allison's -3dB come from?".......
>However, if the sub or subs (or woofers, if we are talking about
>the bass section of a full-range system) are also at a distance
>from room boundaries that equal half that between the subs (or
>woofers) themselves, the effect will be augmented. So, if the
>distance to a boundary is equal to half the distance to the two
>subs, the dip will be 6 dB. If an additional boundary is added
>in, it will grow to 9 dB. The distances do not have to be exact
>for the effect to be cumulative.
>
>The solution is to use a sub/sat system with the crossover set so
>that woofer/woofer and boundary/woofer interference notches
>generated by the satellites are below the sat/sub crossover
>point. The sub should be located so that any boundary/woofer
>related notches in its potential response range would be above
>the crossover point. No big deal. Adding a second sub simply
>reintroduces the problem.
>
>Howard Ferstler
Howard Ferstler
>
> On Wed, 06 Sep 2000 23:07:15 GMT, bigges...@hotmail.com
> (LargeMarge) wrote:
>
> >
> >I know of at least eight (8) RAO-ers
> >who support Howard. And BTW, since
> >we are writing Boonlish, I have received
> >at least eight (8) e-mails supporting me.
> >Ar Har Har Har!!!
> >
> >
> >Marge
> >
>
> Oh wow, eight! That's gotta be a world record! Man!!
Given that many actively posting, RAO types are borderline
lunatics, I am not all that demoralized by having only a few
openly supportive supporters. The ones who post a lot of
scurrilous material here are for the most part a very
juvenile group, at least intellectually, and if I had scads
of followers I would be seriously concerned.
Other than the need to sell books, one of my purposes here
is to have the fringe group draw attention to itself. When
they do that, the results are pretty much as I would want.
Howard Ferstler
Howard Ferstler
> What I really wanted to ask is: "Where does Allison's -3dB come from?".......
While it seems as if the power response would not be effected by
by the interaction of a ray coming from a more distant woofer,
that is indeed what happens to the tune of -3 dB.
Going into the details would involve more time than I have. I
suppose I could just retype the entire texts of his most
important article on the topic right here, but instead I will
just offer up some references. Then, you can read the master's
text directly.
The primary paper on the subject of bass cancellation was: "The
Influence of Room Boundaries on Loudspeaker Power Output," JAES
#22, June, 1974. It outlines the concept pretty exactingly, and
comes complete with all the mathematical proofs and measurement
data. There is a fair amount of math in this paper, and for the
life of me, even if I had the time to type out the text the
mathematical symbols would not be reproducible here.
Three lay-reader-oriented articles on speaker/room interactions
appeared in the British journal Hi-Fi News and Record Review:
December, 1989, February, 1990, and April, 1990. They should have
some simplified data on the phenomenon, as well as other
room-related artifacts.
Another pop-magazine essay appeared in Stereo Review in August,
1975, and it also deals with both speaker/boundary interactions
as well as listener/boundary interactions. Those interactions are
unrelated to standing-wave artifacts, by the way. The Allison
Effect does not involve standing waves. Nor does it just involve
the usual floor-bounce cancellations. It is much broader in scope
than the latter.
Two more technical essays on room/speaker interactions (not
directly related to the Allison Effect, but still interesting,
and also commenting upon it) are: The Sound Field in Home
Listening Rooms, JAES #20, July/August, 1972 and "The Sound Field
in Home Listening Rooms II, JAES #24, Jan/Feb, 1976.
Those who need to learn something about speaker directionality
and how it influences what we hear (another off-topic essay but
still something that might be interesting to sweet-spot devotees)
are referred to "Imaging and Loudspeaker Directivity: To Beam or
Not to Beam," delivered at the October, 1995 convention, and
available from the AES as preprint 4095 (K-4).
Howard Ferstler