Hi-Fi myths - Pointy Feet, Transformers etc
ssod...@cuppa.curtin.edu.au
After reply's to my Speaker Enclosure post I have discovered that much of what
I have been told by my local Hi-Fi expert (I thought) has been crap. So this
message contains some more "facts" which I have been told;
1 - Vibration makes a differnce to the sound of electronic components.
( I never quite beleived this ).
2 - FeedBackless Class-A amps,pre-amps will sound the best, you just
need to use very expensive components. This is of particular interest
as I was going to build a pre-amp using the most basic Class-A design.
3 - Large Transformers make a difference in sound.. I still a sceptic
of this. It has been suggested to me that a pre-amp which requires
1 Amp Max to operate at will benefit from sound huge 50 amp power
supply.. This also apply's to DA converters. Is such a huge-amount
of reserve current required ? With the pre-amp I want to build I was
going to run it from Lead-Acid batteries ( commerical ones.. not just
rechargables ).
4 - Little Pointy feet thingos improve sound of Hi-Fi gear. Not just
used of CD's and T/Tables but also on Pre-Amps etc ?
Can anyone clear these points up ? Im not sure who to believe but 200 netters
can't be wrong... right ?
Thanks in advance,
Daniel.
Curtin Uni.
Western Oztralia.
Francis Vaughan
|>
|> After reply's to my Speaker Enclosure post I have discovered that much of what
|> I have been told by my local Hi-Fi expert (I thought) has been crap. So this
|> message contains some more "facts" which I have been told;
OK, I'm bored, and not feeling the best (a night on the turps) so I'll pass
my jaundiced eye over a few of these.
|> 1 - Vibration makes a differnce to the sound of electronic components.
|> ( I never quite beleived this ).
Not unreasonable actually. Quite a few components can be shown to be
microphonic. Valves (tubes to the unwashed) must be the best example.
It has been noted by a few golden eared that positioning a valve-amp
_nearer_ the speakers can warm the sound up - to their ears anyway.
The issue of jitter in DAC converters occasionally also covers vibration.
Crystals used for internal clocking are prone to microphonic pickup. This
is seen as jitter on the output clock which can manifest itself sidebands
on the recovered sound. Most people don't place their CD players on their
speakers.
Ultimately any component can be made to act as a transducer to some extent.
PC circuit tracks will act as strain-guages as the board flexes. However
one simply needs to take a balanced view. Most of these effects are buried
below the noise floor of the system. Balance is not however something
the average rabid audiophile is well endowed with.
It all comes down to where you are going to spend your money and effort
to best effect. Chasing microphonics may well be a poor start.
|> 2 - FeedBackless Class-A amps,pre-amps will sound the best, you just
|> need to use very expensive components. This is of particular interest
|> as I was going to build a pre-amp using the most basic Class-A design.
This one never seems to go away. Three articles of faith here rolled into
one.
1. Values are best.
2. Class A is best.
3. Feedback is bad.
You left off number 4, pentodes bad, triodes good. Lord only knows where this
one came from.
Number 1 is simply an article of faith. There is nothing like the warm glow
of heater filaments to improve the subjective enjoyment of music.
Class A does have considerable merit, but has become something of a icon.
I wonder how things would have been if the nomenclature for the bias classes
had been devised in a different order. Class-A always has had the name
when no-one has even understood the technical meaning of the term.
Number 3 must be the greatest con, and epitomises the ignorant technobabble
of the golden eared. Perhaps some of the prejudice is rooted in an element
of truth. Poorly applied feedback is has clear simple and real deleterious
effects. If the feedback network has a higher bandwidth than the output
stage it is possible to get a situation where the output stage cannot keep
pace with the feedback. At this point the feedback loop is essentially open.
The amplifier will run at its open loop gain until the loop closes again.
Poor transistor amplifiers suffer from this effect, and because of their
often slower performance valve amps can suffer as well. All that is required
is to understand the design restraints. This stuff is not exactly new.
An all valve, Class-A with no feedback eh? Sounds like a VOX AC-30
to me. One of the nicest guitar amps made IMHO. I covet one of these,
but not as a sound system.
|> 3 - Large Transformers make a difference in sound.. I still a sceptic
|> of this. It has been suggested to me that a pre-amp which requires
|> 1 Amp Max to operate at will benefit from sound huge 50 amp power
|> supply.. This also apply's to DA converters. Is such a huge-amount
|> of reserve current required ? With the pre-amp I want to build I was
|> going to run it from Lead-Acid batteries ( commerical ones.. not just
|> rechargables ).
Very good, keep up the scepticism. Power supply impeadance can effect the
performance of circuits, and yes it seems that a lot of DA converters
have rather overlooked this. To some extent this is part of what you pay
for in higher priced boxes. However quoting the DC current ability of
a supply does almost nothing to aid us here. What we need is to take care,
not of our ability to supply an arc-welder, but to deliver power with adequately
low impeadance at useful frequencies. Care in board layout, bypassing
and selection of regulators are the requisite needs. Not a thumping great
transformer. Like the little glowing lights in the bottles a huge lump
of iron humming away might help the ignorant feel warm and fuzzy inside,
but will not help the quality of sound.
|> 4 - Little Pointy feet thingos improve sound of Hi-Fi gear. Not just
|> used of CD's and T/Tables but also on Pre-Amps etc ?
It would be interesting to get someone to actually make some quantifiable
claim about the physical properties of these overpriced paperweights. A cone
of metal _does_ have some acoustical effect, it will act as an impeadance
transformer. One catch, only at those frequencies whose wavelengths are
small compared to the diameter of the cone. Before anyone gets exited,
remember this is this is at wavelengths not in air, but wavelengths in
the metal. These are seriously high frequencies. Just where they might
be coming from, and why you want some impeadance matching for them is
perhaps a little mysterious.
|> Can anyone clear these points up ? Im not sure who to believe but 200 netters
|> can't be wrong... right ?
Why not, happens all the time :-)
To sumarise. The golden eared continue to expound some amazing ideas, and
seem to have the ability to get one onother to part with extraordinary amounts
of money in support of them. Rarely do they have any basis in fact. Sometimes
there is some underlying physics but when there is, almost without exception,
the actual mathematics is missing. A real physical effect is read about in
some popular science comic, misunderstood, but instantly assumed to have some
enormous effect upon the sound. Soon after a grossly overpriced fix marketed.
Two things are usually missing from the solution to the problem. Any evidence
that the problem does in actual fact have an effect on the sound, and two, that
the marketed device or tweak actually does anything to ameliorate the effect.
Finally! :-)
Finally, golden eared and tweakophiles may occasionally stumble upon something
that is important and even expouse the true explanation. However they won't
know it. Monkeys and typewriters.
Francis Vaughan
Shun-Chang Tsai
> 3 - Large Transformers make a difference in sound.. I still a sceptic
> of this.
Maybe you mean more power??? The size of the transformer should be
irrelevant. The only thing that matters is what it does. (Yes, I know
what it does). How efficient is it? Blah blah blah. However, often
large transformers do better jobs simply because their size is a
result of more circuitry and more "designer" things.
> 4 - Little Pointy feet thingos improve sound of Hi-Fi gear. Not just
> used of CD's and T/Tables but also on Pre-Amps etc ?
I know they don't work for CDs or Amps. I can't hear it, at least. I
have played with the best of them as well.
David Stockton
: After reply's to my Speaker Enclosure post I have discovered that much of what
: Thanks in advance,
I'm not qualified to answer your last question, but I know who is.
P T Barnum could give you a fairly good answer.
There are plenty of people who do know what they are doing, but there
are sufficient others who only think they know, to make two games
possible:
1) The snake oil merchant makes/sells things which have no reliable
benefit and may even be a detriment. If he knows this he is a crook, but
it's not illegal. It is not uncommon for the people making and selling
ineffective improvements to really and truely believe they work. In the
human mind belief can overcome experience. At some time or another, all
of us sees/hears what we want to see/hear and never know that we've
missed something. Some of these people's products do work as well as
anything available, it is the claim of being even better still that is
the fault.
2) The snob is proud of his equipment. Being proud of it is more
important than enjoying music. He has a strong preference for very
expensive things, mostly to be seen having something rare (because few
can afford) He has a strong preference for things which are in short
supply. If it is rare because it uses strange and unusual materials this
is good, if it was made by a wizened guru who only carves one out of the
solid every year when the astrology is right, this is doubly good.
These people quite often assemble systems that work well, but they
have probably overdone a number of things that were unnecessary and
missed a few tricks, and spent an amazing amount of money.
Me ? I've caught myself a few times believing something despite
evidence in front of my face. There is no way of knowing how many times
I've done this but not known. I've caught myself trying to impress
others too.
Evidence... Look at all the mods changes and replacements of
equipment where the effects are described as major, phenomenal, large,
obvious, significant, staggering. Where are the descriptions of "I can't
tell any difference" slight, small, "Not worth bothering with" etc ?
Some of the beliefs stem from perfectly valid seeds:
Big transformers give better output regulation, and this is important
in some cases. becomes Big transformers give improvements in ALL cases.
Some people have used feedback badly. Becomes all feedback is bad.
Skinny speaker wire causes degradation of sound quality has become a
race for the most expensive, most esoteric metallurgy.
The general assumption is that if something produces a benefit in some
circumstances, it will always produce a benefit, although it may be
smaller, in other circumstances. What is lacking is a knowledge of where
an improvement becomes small enough to be unnoticable, and recognition
of circumstances where it may be a degradation instead.
Look at some of the for sale postings, there are some individuals
frequently selling recently bought equipment. Why ? some of them seem
reasonable and honest types who describe their cast-offs, quoting good
points and bad points in their opinions. I do not criticise these
people, they seem to enjoy their hobby and constitute a source of
bargain high class equipment. I just point to their existance as
something that makes me think that other people besides myself find a
lot of "improvements" difficult to decide on.
As a professional electronics designer, I've designed a lot of my own
equipment, for the fun of it, and to be a bit individualistic. I would
never publish any of this or allow it to be manufactured because I find
the lack of objectivity in this field frightening, and I fear it would
be judged on strange, unpredictable and often irrelevent criteria. In
other areas of electronics I have no problem with any lack of confidence
in my work.
Sometimes we haven't worked out what to measure. and this has given
rise to the assumption:
"Everyone agreed that the amplifier with the lower distortion figure
actually sounded worse than that with the better one" has lead to " All
measurements are bad, misleading, wrong and anathema"
Based on this, scientific method, proof, objectivity, measurement,
have become unfasionable.
Just my own personal musings.
David
Thomas W. Matthews
Francis Vaughan wrote a great response to the above referenced article.
It was informative, and sounded to me like a well-balanced,
reasonable viewpoint.
On the question about feedback, I agree with Francis that a poor
design can use feedback, perhaps to improve one or two specs, but
still sound bad. Indeed, feedback must be used in some form.
The relationship between BJT collector current and base-emitter
voltage is exponential. The relationship between drain current
and gate-source voltage of a FET follows a square-law relationship.
The only input-output relationship of a solid state device
that is linear (or close, within limits) is that of collector
current to base current - and that would be difficult to exploit
for an audio amplifier because it's not well controlled.
I'm not as well acquainted with valves (tubes), but I believe that
simple valve types also follow a square-law relationship (between
plate current and grid-cathode voltage?). Are multiple grid tubes
capable of a linear transfer characteristic without feedback? If
so, is it well-controlled and useable for an audio amplifier?
I have one other question, related to Francis' comment:
In article <2cfart$9...@huon.itd.adelaide.edu.au>,
fra...@cs.adelaide.edu.au (Francis Vaughan) writes:
(deletions)
|> Number 3 must be the greatest con, and epitomises the ignorant technobabble
|> of the golden eared. Perhaps some of the prejudice is rooted in an element
|> of truth. Poorly applied feedback is has clear simple and real deleterious
|> effects. If the feedback network has a higher bandwidth than the output
|> stage it is possible to get a situation where the output stage cannot keep
|> pace with the feedback. At this point the feedback loop is essentially open.
|> The amplifier will run at its open loop gain until the loop closes again.
|> Poor transistor amplifiers suffer from this effect, and because of their
|> often slower performance valve amps can suffer as well. All that is required
|> is to understand the design restraints. This stuff is not exactly new.
I usually think of a feedback network as passive (although one might
replace it with a two-port network with a controlled source for
analysis). That's why I can't understand what a feedback network might
be doing that "the output stage cannot keep pace" with it, since the
output network _drives_ the feedback network. The feedback network
simply conveys a portion of an output quantity back to the input
and generally speaking, the faster it does it, the better.
I don't think that bandwidth limits (a linear phenomenon) could
cause an intermittent opening of the feedback loop. I'm curious
as to what Francis is describing; I think he could be talking about
the transient intermodulation distortion problem, but the details
don't quite fit. I'll describe the situation as I see it, but I'm
open to some new ideas.
The feedback loop is not opened unless some stage in the loop
"hits" a severe non-linearity. For example, if the output of the
amplifier runs into its voltage swing limitation, the loop can be
considered open. This is so because the input to the forward amplifier
should be a combination of the input to the amplifier circuit and
the feedback. When the output of the forward amplifier is "not
what it's supposed to be" then the feedback is not right either, and
in the case of hard clipping on the output, the feedback is gone.
Another type of non-linearity is time-dependent. Suppose that some
stage of the forward amplifier has a slew-rate limit (a limited
dV/dt). Then if the input to the circuit changes rapidly enough,
the output of the forward amplifier will not get where it's supposed
to be for some period of time. While the output is trying to catch
up, the forward amplifier is operating with its open loop dynamics,
in response to an input overdrive. (The input is overdriven because
the correct amount of feedback is required to decrease the input of
the foreward amplifier to a reasonable value; until the output reaches
its correct value, the feedback will not be correct either.)
I would rather not say that an amplifier is operating at its open
loop gain while its slewing. That's another discrepancy between what
Francis wrote and the situation as I envision it that leads me to
think we may be talking about different things.
Tom Matthews
matt...@ece.ucdavis.edu
Russell DeAnna
>> 4 - Little Pointy feet thingos improve sound of Hi-Fi gear. Not just
>> used of CD's and T/Tables but also on Pre-Amps etc ?
>
>I know they don't work for CDs or Amps. I can't hear it, at least. I
>have played with the best of them as well.
Before you condemn an application of a theory with your own limited experience,
you should thoroughly explore different cases. Maybe you could hear
no difference in your system, but this doesn't mean that another system
would not benefit from the addition of vibration control devices.
I have not yet tried the cone-shaped, vibration-isolation feet, but
I finished making a set just yesterday. I tried placing four under my
CD player last night. This was impossible---the player was
unstable atop the cones. I'll either have to shorten the cones or
add screws between the cones and the player's base to make it stable.
These cones were made with a 60 degree angle and are 2 inches in
diameter at the base. I also left a two-inch cylinder adjacent to
the base. This was the portion held by the lathe. So I could easily
shorten the cones by cutting off the base.
--
Russell DeAnna NASA Lewis Research Center, Cleveland, Ohio
to...@tolstoy.lerc.nasa.gov
Shun-Chang Tsai
>In article <stsai.753610560@scws1> st...@scws1.harvard.edu (Shun-Chang Tsai) writes:
>>> 4 - Little Pointy feet thingos improve sound of Hi-Fi gear. Not just
>>> used of CD's and T/Tables but also on Pre-Amps etc ?
>>
>>I know they don't work for CDs or Amps. I can't hear it, at least. I
>>have played with the best of them as well.
> Before you condemn an application of a theory with your own limited experience,
> you should thoroughly explore different cases. Maybe you could hear
> no difference in your system, but this doesn't mean that another system
> would not benefit from the addition of vibration control devices.
Could be. But I tested it on more than just one system. More like 10
or 20 different CD players. I've also tried them on amps. However, I
haven't tried them on LP players or speakers. I've only tried on one
high-end CD transporter, though.
> I have not yet tried the cone-shaped, vibration-isolation feet, but
> I finished making a set just yesterday.
Tried that. I didn't hear the difference. Maybe it's just me. Maybe
you need the right combination to make it work. I dunno. If you find
out anything, please tell me.
Then again, that was about 8 years ago. I was not even in my teens
then, so I might have been confused or something. I never really
trusted my memory. It's just one of those things.
th...@sushi.uib.no
>
> An all valve, Class-A with no feedback eh? Sounds like a VOX AC-30
> to me. One of the nicest guitar amps made IMHO. I covet one of these,
> but not as a sound system.
>
Well, maybe you should give a listen to a Conrad Johnson all tube
class-A with no-feedback amp - it is definately something to
covet in any high-end high-fi system... Personally, I haven't yet
begun compared listening feedback vs. no-feedback, but I liked
your explination. My preamp uses local feedback (Electrocompaniet
EC-4), but I can't complain about the sound. Maybe if I buy a
better power amp? ;-)
>
> |> Can anyone clear these points up ? Im not sure who to believe but 200 netters
> |> can't be wrong... right ?
>
> Why not, happens all the time :-)
>
>
> Francis Vaughan
Any thoughts on those strange green pens to paint CD edges with???
Regards,
--
Thor Legvold | "This is the strangest life
NorNeXT User Group leader | I've ever known..."
University of Bergen | -Jim Morrison, The Doors
NORWAY | ed...@edb.uib.nolt of your source, and
can make your $1 座
Chris Gee
assuming a fairly rigid cabinet, cone movement COULD
cause excess motion to the entire speaker on a carpeted
floor. the spikes would penetrate the carpet and couple
the speaker to the floor, thus saving a few ergs for
proper cone motion. theoretically, their effect is best
for cement or cement-based floors. obviously, coupling a
speaker to a wood floor on say, a second story would be
less than optimal. the theory is to reduce/eliminate
"smearing" from im-perfect speaker motions.
what about bricks on amps? a few years back that was
a big fad. anybody got any results to report?
============================================================================
Christopher W Gee (ch...@fa.disney.com) | "...this program WORKS, it just
Walt Disney Feature Animation | doesn't compile..."
Glendale, CA 91221 (818)544-2505 | "...that's as white as it gets,
| all the bits are on..."
============================================================================
Greg Scullard
> 1) The snake oil merchant makes/sells things which have no reliable
>benefit and may even be a detriment. If he knows this he is a crook, but
>it's not illegal. It is not uncommon for the people making and selling
[More deleted stuff]
To test your dealer, ask him to demonstrate the difference this item he's
selling you is actually making. If YOU can't hear it, don't buy it, he's
probably a crook or has better ears than yours and there is no reason why
you should improve on a system if you can't hear the difference. You don't
change your wallpaper if you're blind do you !
The above applies for speakers, interconnects (whichever way they are supposed
to be connected), cables (However the AC signal should flow), pointy things...
>
> 2) The snob is proud of his equipment. Being proud of it is more
>important than enjoying music.
[Stuff deleted]
Then you shouldn't be worried about spending your money at all, any way you
spend it must be wise, regardless of the improvements your new acquisition
makes or not.
I have had the same system for a year and a half now, very happy with it (It'
not all high end) but was very careful in choosing the separates in my own time
with my own judgement and by listening to various makes and models. I have
tried to change the way my speaker cables are connected (To have the signal
flow like the arrow on the cable say) and did not find a difference, I guess
I couldn't hear it. I also listened to the Chesky recording using different
interconnects, as they suggest and no difference, must be my hearing...
My own contribution.
Greg
--
-------------------------------------------------------------------------------
"C'est mieux que si c'etait pire" Coluche.
-------------------------------------------------------------------------------
Richard D Pierce
Given the source (disney.com), it's difficult to decide whether this is
serious or not :-)
>putting spikes on your speakers couples them to the floor;
>assuming a fairly rigid cabinet, cone movement COULD
>cause excess motion to the entire speaker on a carpeted
>floor. the spikes would penetrate the carpet and couple
>the speaker to the floor, thus saving a few ergs for
>proper cone motion. theoretically, their effect is best
>for cement or cement-based floors. obviously, coupling a
>speaker to a wood floor on say, a second story would be
>less than optimal. the theory is to reduce/eliminate
>"smearing" from im-perfect speaker motions.
Well, ahem...
Do we care to calculate exactly the effect. I did this as an excercise a
number of years ago here on internet. The effects or not "a few ergs of
cone motion", especially since cone motion doesn't come in ergs, it comes
in m/s.
Be that as it may, simply looking at Newton's third law, conservation of
momentum and all that, one can easily calculate that the effects are
miniscule, at best. For example, a hypotheticla speaker weighing, say, 20
kg with an 8" woofer with an effective cone mass of 25 g moving .5 cm
peak at 50 Hz results in the cabinet moving, lessee...
v = 2 pi f Xmax = 6.28 * 50/sec * 5x10^-3m = 1.57 m/sec
Then the total momentum is:
m0 = v*m = 1.57 m/sec * 25x10^-3kg = 3.9x10^-2 kg m/sec
Since momentum is conserved:
mv + MV = 0
or
mv = -MV
then, by substituion, the peak velocity of the enclosure is:
3.9x10^-2 kg m/sec = MV = 20 kG * V
rearanging, we get:
3.9x10-2 kg m/sec
----------------- = V = 1.95x10^3 m/sec
20 kg
The cabinet (which, for the above calculations, we presume is attached to
NOTHING, it is free floating about in thin air to move as its woofer
dictates) moves at a whopping PEAK velocity of 1.95x10^-3 m/sec. That
translates to a peak amplitude on the order of 6x10-6 m, or 6 microns, as
in millionths of a meter.
There are a variety of effects that can be invoked to suggest what
audible effects such motion may have. One popular mechanism is the
doppler effect, where the cabinet vibrating back and forth causes
essentially an FM modulation of the original. The peak deviation will be
equal to:
c
f' = f ------
c +- v
A 1 kHz tone will have a peak deviation, assuming maximumpeak cabinet
velocity, from above, of 1.95x10^-3 m/sec and a velocity of sound c of
3.45x10^3 m/sec is
345 m/sec
1 kHz -------------
345 +- .00195
or a deviation of +- 0.0000057 Hz
Needless to say, this number is orders of magnitude less than the
deviations found in the best studio quality tape machines, as many as two
orders of magnitude less than high-grade consumer analog playback
equipment, and probably an order or two better than found on high-quality
digital playback equipment.
It might be asserted that spikes and such have an audible effect. The
proponents of such have yet to unequivocably demonstrate this. The point
to the above excercise is NOT to say that such an effect does NOT exist.
Rather, the common mechanism invoked above is, because of the
ridiculously low numbers involved, is VERY LIKELY NOT the cause of such
alledged effects. Rather than tilting at such physical windmills, the
proponents of spikes and such had better spend their efforts instead at
breathing some credibility into their claims .
>what about bricks on amps? a few years back that was
>a big fad. anybody got any results to report?
Well, I have an apochryphal tale of the effect of bricks. A firend of
mine claimed that bricks made a fantastic difference, to the point where
he claimed the more bricks the better. The last I saw of him, he was
crying over an amplifer that had blown itself to smithereens because he
had so many bricks on it, it bent the top cover enough to short out the
power supply capacitors.
--
| Dick Pierce |
| Loudspeaker and Software Consulting |
| 17 Sartelle Street Pepperell, MA 01463 |
| (508) 433-9183 (Voice and FAX) |
Rick Brusuelas
> putting spikes on your speakers couples them to the floor;
> assuming a fairly rigid cabinet, cone movement COULD
> cause excess motion to the entire speaker on a carpeted
> floor. the spikes would penetrate the carpet and couple
> the speaker to the floor, thus saving a few ergs for
> proper cone motion.
It has been a long time since I even saw cone-shaped mounts
designed to be placed under components, but if my shaky memory
serves me right, I thought the "theory" behind those things
was that they increase the effective mass of the component
by concentrating the weight onto the smallest point. And
as I recall, there was some thought back then that the
heavier the component, the better (for reducing susceptibility
to vibrations. As I recall, these were especially popular
with turntables.
Sorry if my description contradicts physics or anything.
never bought the things, though I wish I had (they looked
cool). But I was too busy using green felt pens and
Armorall on my CDs ;-).
Rick Brusuelas
Sun Library
Russell DeAnna
>to...@tolstoy.lerc.nasa.gov (Russell DeAnna) writes:
>
>> I have not yet tried the cone-shaped, vibration-isolation feet, but
>> I finished making a set just yesterday.
>
>Tried that. I didn't hear the difference. Maybe it's just me. Maybe
>you need the right combination to make it work. I dunno. If you find
>out anything, please tell me.
>
>Then again, that was about 8 years ago. I was not even in my teens
>then, so I might have been confused or something. I never really
>trusted my memory. It's just one of those things.
Like I said in my previous post, I can't use my cones as
currently configured since the CD player is unstable when
placed above four of them. It may be some time before
I can modify these cones, but I could turn them up-side-down
(points facing upwards) without modification. I don't expect
much of an improvement, but I operate under the idea that if
a tweek doesn't defile the sound, and has some technical merit,
then go ahead and use it.
Mike Glantz
>It might be asserted that spikes and such have an audible effect. The
>proponents of such have yet to unequivocably demonstrate this. The point
>to the above excercise is NOT to say that such an effect does NOT exist.
>Rather, the common mechanism invoked above is, because of the
>ridiculously low numbers involved, is VERY LIKELY NOT the cause of such
>alledged effects. Rather than tilting at such physical windmills, the
>proponents of spikes and such had better spend their efforts instead at
>breathing some credibility into their claims .
I will claim that cones or spikes under speakers can have a significant
perceptible effect, but, as Dick points out, *not* because of any improvement
in cone motion. If you live in a wood-frame building such as the typical
house in the northeastern US, a tight coupling to the floor transmits a
very noticeable amount of mechanical energy to your feet. Bass you can
really feel, as they say. The psychoacoustic affect of this is not small,
and could easily be described as "tight" bass.
--
Mike Glantz Digital Equipment Corporation
gla...@tay1.dec.com Littleton, MA, USA
Dan Kerl
series of articles that started with the August '93 issue of Electronics
World + Wireless World. Douglas Self (the author) analyzes modern amplifier
design with an eye towards identifying the individual mechanisms present
that are responsible for distortion, plus suggestions on how to minimize
their effects. Sure beats those 'snake oil' descriptions I've been hearing
on this subject. Definitely worthwile reading (it has been for me, anyway).
Dan Kerl
dlk...@cmack.b11.ingr.com
Louis K. Scheffer
[Calculation of speaker movement showing movement is small deleted...]
>It might be asserted that spikes and such have an audible effect. The
>proponents of such have yet to unequivocably demonstrate this. The point
>to the above excercise is NOT to say that such an effect does NOT exist.
>Rather, the common mechanism invoked above is, because of the
>ridiculously low numbers involved, is VERY LIKELY NOT the cause of such
>alledged effects.
When spikes are added, there are at least two possible mechanisms that
yield larger (and maybe audible) effects:
1) Moving the speakers a few cm higher
In order to test the effects of spikes, you should compare them
with non-spike supports of the same size, not with the same speakers
without spikes. Otherwise you are comparing two changes at once, and
small changes in speaker placement can certainly be audible.
2) Changing the vibrational modes of the cabinet panels.
Vibrational modes of the cabinet panels affect the response in ways
that are easy to measure (try a cabinet with and without internal
bracing) and I think audible, though I've never tried a test with
only this one change. An interesting "spike" experiment would be to try
the spikes in different positions with respect to the cabinet, and
see if you can measure any differences.
So it seems plausible that changing your system to use spikes might change
the sound, but as Dick says the mechanism is probably not the prevention
of speaker movement.
Lou Scheffer
Chris Christensen
>In article <CGqtB...@world.std.com>, DPi...@world.std.com (Richard D Pierce) writes:
>>It might be asserted that spikes and such have an audible effect. The
>>proponents of such have yet to unequivocably demonstrate this. The point
>>to the above excercise is NOT to say that such an effect does NOT exist.
>>Rather, the common mechanism invoked above is, because of the
>>ridiculously low numbers involved, is VERY LIKELY NOT the cause of such
>>alledged effects. Rather than tilting at such physical windmills, the
>>proponents of spikes and such had better spend their efforts instead at
>>breathing some credibility into their claims .
Once again we are treated to Dick's clear sense of purpose! To stamp
out the hogwash!
I haven't been following all of the discussion on this thread. That
hasn't stopped me from commenting in the past and it won't now!
>I will claim that cones or spikes under speakers can have a significant
>perceptible effect, but, as Dick points out, *not* because of any improvement
>in cone motion. If you live in a wood-frame building such as the typical
>house in the northeastern US, a tight coupling to the floor transmits a
>very noticeable amount of mechanical energy to your feet. Bass you can
>really feel, as they say. The psychoacoustic affect of this is not small,
>and could easily be described as "tight" bass.
IMHO:
1. The most important aspect of the listening experience is the acoustics
of the room.
2. The "quality" of the speakers used for listening.
3. Everything else!
I believe that speakers should be decoupled from the floor, walls, etc
in the room. This decoupling can be done with a resilient material or
with a material that is as insensitive to being driven by the speaker
cabinet as possible.
I have and currently use a dense foam cushion under the smallish
speakers I have in my studio (I use dual subs to help the little
speakers go below their 60 Hz low end).
The speakers sit atop an equipment bridge. Under substantial
listening levels there is no transmission of sound from the cabinet
(which is quite silodly built anyway).
For heavier and or floor standing speakers I like to use concrete! I
find this medium to be resistant to being driven by the speakers
cabinet vibrations! I would use a dense rubber mat between the
concrete speaker stand and the speaker, something like a typewriter
mat.
Have a nice day!
--
D.R. Chris Christensen Grass Valley Group (the day job)
chr...@gold.gvg.tek.com P.O. Box 1114 mail Stop N32B
916-478-3419 FAX 916-478-3887 Grass Valley, CA 95945
Neither I nor my employer is responsible for anything I say or do.
Stuart Krivis
D->.std.com>
D->Newsgroup: rec.audio
D->Organization: The World Public Access UNIX, Brookline, MA
D->In article <2chf1a...@marvin.is.wdi.disney.com> ch...@fa.disney.com (Chris
D->Gee) writes:
D->Given the source (disney.com), it's difficult to decide whether this is
D->serious or not :-)
D->There are a variety of effects that can be invoked to suggest what
D->audible effects such motion may have. One popular mechanism is the
D->doppler effect, where the cabinet vibrating back and forth causes
I am especially concerned about the Doppler effect generated by cone
movement. As such, I am designing a forty (40)-way loudspeaker
system. Cone movement at one frequency will be much less likely to
modulate another frequency with this many drivers. Crossovers will
all be 4th-order active. Several amplifier manufacturers have
expressed interest in my design.
(humor mode OFF - Y/n)
>what about bricks on amps? a few years back that was
>a big fad. anybody got any results to report?
D->Well, I have an apochryphal tale of the effect of bricks. A firend of
D->mine claimed that bricks made a fantastic difference, to the point where
D->he claimed the more bricks the better. The last I saw of him, he was
D->crying over an amplifer that had blown itself to smithereens because he
D->had so many bricks on it, it bent the top cover enough to short out the
D->power supply capacitors.
I would think that many amps have died an early death due to having
"magic bricks" covering their cooling vents.
... Foo Mail * It's a dessert topping AND a floor wax!
stuart...@pcohio.com OR bp...@cleveland.freenet.edu
---
ş SPEED 1.4i #1424 ş I tried the rest and now use the best! SPEED READ!
JG...@esoc.bitnet
Dear Stuart Krivis and other listen-inns,
It'snice to read that others are concerned about a seemingly
serious flaw in loudspeaker design - DOPPLER distortion, however
IF THAT WAS THE CASE I'M SURE SOMEONE HAD PATENTENDED THIS IN 1936....
...and no wonder the amp manufacturers are interested. If your idea
(Your? idea) catches on they will sell 40 amps for each Stuart Klevis
Model One speaker set.......:-)
This news group is really entertaining........:-) :-) :-)
Regards JG :-)
Matt Kennel
: Well, ahem...
: Do we care to calculate exactly the effect. I did this as an excercise a
: number of years ago here on internet. The effects or not "a few ergs of
: cone motion", especially since cone motion doesn't come in ergs, it comes
: in m/s.
: Be that as it may, simply looking at Newton's third law, conservation of
: momentum and all that, one can easily calculate that the effects are
: miniscule, at best. For example, a hypotheticla speaker weighing, say, 20
: kg with an 8" woofer with an effective cone mass of 25 g moving .5 cm
: peak at 50 Hz results in the cabinet moving, lessee...
:
: v = 2 pi f Xmax = 6.28 * 50/sec * 5x10^-3m = 1.57 m/sec
: Then the total momentum is:
: <deleted>
: The cabinet (which, for the above calculations, we presume is attached to
: NOTHING, it is free floating about in thin air to move as its woofer
: dictates) moves at a whopping PEAK velocity of 1.95x10^-3 m/sec. That
: translates to a peak amplitude on the order of 6x10-6 m, or 6 microns, as
: in millionths of a meter.
: There are a variety of effects that can be invoked to suggest what
: audible effects such motion may have. One popular mechanism is the
: doppler effect, where the cabinet vibrating back and forth causes
: essentially an FM modulation of the original. The peak deviation will be
: equal to:
: c
: f' = f ------
: c +- v
: A 1 kHz tone will have a peak deviation, assuming maximumpeak cabinet
: velocity, from above, of 1.95x10^-3 m/sec and a velocity of sound c of
: 3.45x10^3 m/sec is
: 345 m/sec
: 1 kHz -------------
: 345 +- .00195
: or a deviation of +- 0.0000057 Hz
This effect is obviously insignifcant. But you're neglecting all the
force of the air (both in and out) on all the parts of the cabinet. And
when the cone pushes "out", the air pushes "back".
Maybe it really is insignificant, but on (cheap) speakers, I find it quite
easy to feel significant low-frequency vibrations of the cabinet right by
the tweeters. Clearly the amplitude is much larger than the amplitude of
the tweeter excursion (who can feel tweeters move with their fingers? I
can't). I guess this is much more likely to be various internal
"vibrational modes" rather than bulk movement of the center of mass.
Obviously I agree with you that "recoil" due to momentum
conservation of cone movement is insignificant.
Whether special speaker points make any difference is yet another
question.
: --
: | Dick Pierce |
: | Loudspeaker and Software Consulting |
: | 17 Sartelle Street Pepperell, MA 01463 |
: | (508) 433-9183 (Voice and FAX) |
--
-Matt Kennel m...@inls1.ucsd.edu
-Institute for Nonlinear Science, University of California, San Diego
-*** AD: Archive for nonlinear dynamics papers & programs: FTP to
-*** lyapunov.ucsd.edu, username "anonymous".
Richard D Pierce
>Richard D Pierce (DPi...@world.std.com) wrote:
>
>This effect is obviously insignifcant. But you're neglecting all the
>force of the air (both in and out) on all the parts of the cabinet. And
>when the cone pushes "out", the air pushes "back".
No, I am not neglecting that. The total air mass load is included in the
calculations. In fact, the actual air mass load is quite small comapred
to the simple inertial mass of the cone, thus contributes little to the
total effect. In fact, for an 8 inch cone in a typical sized baffle, only
a couple or so grams of the total moving mass is the actual part
contributed by the air load.
>Maybe it really is insignificant, but on (cheap) speakers, I find it quite
>easy to feel significant low-frequency vibrations of the cabinet right by
>the tweeters. Clearly the amplitude is much larger than the amplitude of
>the tweeter excursion (who can feel tweeters move with their fingers? I
>can't). I guess this is much more likely to be various internal
>"vibrational modes" rather than bulk movement of the center of mass.
Ah, but this is a completely different effect. You're talking about
cabinet vibrational modes, which I agree can be a significant issue, one
which is not controllable in any meaningful way by "pointy feet".
>Obviously I agree with you that "recoil" due to momentum
>conservation of cone movement is insignificant.
But that is, regrettably, the argument advanced by many advocates of the
devices.
Kurt Strain
: Ah, but this is a completely different effect. You're talking about
: cabinet vibrational modes, which I agree can be a significant issue, one
: which is not controllable in any meaningful way by "pointy feet".
: >Obviously I agree with you that "recoil" due to momentum
: >conservation of cone movement is insignificant.
: But that is, regrettably, the argument advanced by many advocates of the
: devices.
So you don't see any reason to spike a speaker into a floor, and you don't
have any recommendation to do so? Or are you saying you know the real reason
is something else? Come on, tell us your what you think.
Richard D Pierce
>
>So you don't see any reason to spike a speaker into a floor, and you don't
>have any recommendation to do so? Or are you saying you know the real
>reason is something else? Come on, tell us your what you think.
No, I am not saying any of this. What I said is that the reasons advanced
heretofore were inadequate for explaining the phenomenon because the
reasons advanced don't work the way described, are badly formulated, or
are capable of being tested in straightforward fashions and fail those
tests in unambiguous ways.
I am also further saying the many of the staunchest supporters of the
tweak have yet to demonstrate in a reasonably reliable fashion that the
audible phenomenon is real and demonstrable. I have been invited by
several private citizens and two companies who insisted that in THEIR
setup, the differences were OBVIOUS.
In every single case, using THEIR testing and demonstration methodology,
not only was I not able to hear unambigous differences they claimed, BUT
NEITHER WERE THEY! I have never been witness to such sloppy techniques,
silly handwaving and all around comedy. Spikes were added but speakers
were accidently hooked up out of phase, or channel levels were bumped, or
any one of a number of excuses were offered to explain why the "bvious"
differences seemed to have vanished without a trace. I simply sat back
and watched, they did all the work, it was, after all, their show.
Matt Kennel
: >Richard D Pierce (DPi...@world.std.com) wrote:
: >
: >This effect is obviously insignifcant. But you're neglecting all the
: >force of the air (both in and out) on all the parts of the cabinet. And
: >when the cone pushes "out", the air pushes "back".
: No, I am not neglecting that. The total air mass load is included in the
: calculations. In fact, the actual air mass load is quite small comapred
: to the simple inertial mass of the cone, thus contributes little to the
: total effect. In fact, for an 8 inch cone in a typical sized baffle, only
: a couple or so grams of the total moving mass is the actual part
: contributed by the air load.
Oh I didn't look carefully enough. Good job. Nice to know the 'real
numbers'.
: >Maybe it really is insignificant, but on (cheap) speakers, I find it quite
: >easy to feel significant low-frequency vibrations of the cabinet right by
: >the tweeters. Clearly the amplitude is much larger than the amplitude of
: >the tweeter excursion (who can feel tweeters move with their fingers? I
: >can't). I guess this is much more likely to be various internal
: >"vibrational modes" rather than bulk movement of the center of mass.
: Ah, but this is a completely different effect. You're talking about
: cabinet vibrational modes, which I agree can be a significant issue, one
: which is not controllable in any meaningful way by "pointy feet".
So here's the followup: Can excitation of these low-frequency cabinet
vibrational modes contribute to signficant doppler distortion on high
frequency drivers? Is this a signficant effect?
If so, how would one prevent this? (honestly, folks, I'm not a shill
despite what it looks like.... :-) )
Another question: even without significant cabinet vibrations, can the
low-frequency sound exert a signficant enough force on the high-frequency
driver, or its mounting, to induce distortion by this or another mechanism?
This seems like a fundamental consideration---does the low-frequency sound
interact significantly with the HF driver, specifically, to what extent
is 'superposition' upheld in raw physical reality?
: >Obviously I agree with you that "recoil" due to momentum
: >conservation of cone movement is insignificant.
: But that is, regrettably, the argument advanced by many advocates of the
: devices.
In your opinion, do 'pointy feet' or any other speaker 'mounting device'
have significant auditory value?
: --
: | Dick Pierce |
: | Loudspeaker and Software Consulting |
: | 17 Sartelle Street Pepperell, MA 01463 |
: | (508) 433-9183 (Voice and FAX) |
--
JASEN JACOBSEN, ISD, TPA, (813)532-2619
> In your opinion, do 'pointy feet' or any other speaker 'mounting device'
> have significant auditory value?
>
YES! Pointy feet definitely make a difference. (At least they did for
me.)
I have a pair of Paradigm 3se MKIIs on Paradigm's metal stands,
sitting on a hardwood floor. Initially, I did not use the spikes that
came with the stands as I did not want to scratch or otherwise mark the
floor. Music seemed to come from mainly between and behind the speakers
with a good feeling of depth to the sound stage. e.g. There was often a
feeling of instruments and singers being in front of, or behind each
other. Sound (especially movie soundtracks) with extremely left or right
information did not reach beyond the speakers.
Finally I broke down and tried the spikes. The sound stage now seems to
fill the entire end of my room. There is less depth, and the sound seems
much more forward than before, but I prefer the sound with spikes over
that without. I would compare the change to be like going from a seat
near the middle of an intimate club to a front row seat of a small
concert hall.
I'll let the engineering types out there crunch the numbers on what
exactly is going on, but there is a dramatic difference.
The effects of spikes may be less dramatic in a room with heavy
carpeting and heavy curtains, but in my spartan bachelor pad the
change is quite obvious.
- Jasen.
David Stockton
: No, I am not saying any of this. What I said is that the reasons advanced
: heretofore were inadequate for explaining the phenomenon because the
: reasons advanced don't work the way described, are badly formulated, or
: are capable of being tested in straightforward fashions and fail those
: tests in unambiguous ways.
: I am also further saying the many of the staunchest supporters of the
: tweak have yet to demonstrate in a reasonably reliable fashion that the
: audible phenomenon is real and demonstrable. I have been invited by
: several private citizens and two companies who insisted that in THEIR
: setup, the differences were OBVIOUS.
Cabinet motion due to the reaction to the force accelerating the mass
of a cone + air is certainly small, and the Doppler modulation due to
movement of other drivers will be pretty much as Dick has calculated.
The only area of doubt remaining is whether even this amount is audible.
I don't think so, but I accept that there are some people I could never
convince, even though there are orders of magnitude involved.
Perhaps it may be selfish to ask "Why bother", after all, these
people are throwing only their own money away. If I cannot convince
them, then at least there is some fairness that they can never get
me to be impressed with their tweaks. I genuinely cannot hear any
noticable difference in most cases, and in a lot of cases, on hearing,
or thinking I hear a difference I cannot put hand on heart and say which
is better. Is my hearing so much worse than theirs ? am I so
imperceptive ? how can I tell what it is like to hear through someone
else's ears. Or they, mine
When I do hear some effect, I want to find out the mechanism
involved, just guessing what to blame is easy, but not good enough.
Dick's sort of calculations are a great help at appreciating the scale
of things to help plan experiments to properly test hypotheses. There is
too much blind faith in guru's guesses, and too much rejection of
open-minded information gathering by calculation and measured
experiment.
Particularly:
If pointed feet are driven hard into the floor, does it really stop a
speaker on a stand swaying? Are floors really stiff and low Q enough to
always make this an improvement? A low impedence vibration generator on
a long cantilever is not so simple to control.
If someone is listening at high levels, will sound induced vibration
cause the position of their ears to move? can an improvement be
obtained by clamping the head to a stand fitted with the de rigeur sharp
feet nailed into the floor ?
I'm not trying to be deliberately awkward, I just have difficulty
believing everything I'm told, I want to find out what mechanisms are in
action, I want to know the scale of things. Dick's calculation is fine,
testable and provable, but the people who have said that this much
movement must be creating some difference they have percieved are just
guessing. Now guesses can be right, but I see no discussion of other
possible mechanisms, I see no discussion of why they were eliminated as
possibilities. I cannot accept Autos-da-fe and guesses as being good
enough.
Absolute belief wihout support can be a lucrative form of gullibility.
Help is available from people long dead, Bacon and Occam ;-)
Personal beliefs of David Stockton
Richard Heck
missed the point. The point of spiked feet is not so much to rigidify the
speaker itself as to _isolate it from the floor_. If one has a solid base,
the thing is not going to rock. The rigidity of the stand itself is much
more important. The problem is that vibration can be transferred from the
speaker cabinet to the floor, which then acts as a huge cone, muddying the
sound (and annoying your neighbors, if you live in an apartment). I for
one can attest to a _huge_ improvement after trading rubber pads for
spiked feet on my stands.
Yours,
rh
John Lee
>Yours,
>rh
=========================================
I agree. I, my brother, my girlfriend all observed/heard _huge_
improvement in the bass after lifting the speakers off the carpet with
pointy feet.
Regards,
John
Mike Glantz
>I agree. I, my brother, my girlfriend all observed/heard _huge_
>improvement in the bass after lifting the speakers off the carpet with
>pointy feet.
>
>Regards,
>
>John
While I don't have data to prove it, I believe that spikes *improve*
the coupling between the cabinet and the floor, rather than increasing
the isolation. It is the enhanced transmission of mechanical energy
to the body, through the floor, which gives the strong and real
sense of more powerful bass.
This will be most noticeable on wooden floors. If this hypothesis is
correct, then it should be possible to notice a much lesser improvement
when using spikes on cement slab floors. Of course, that would imply
trying to conduct some sort of experiment which controlled for subjective
effects.
Unknown
I believe that the most recent issue of _Stereo_Review_ has an article on the
benefits of different speaker stand types. It includes a blind test which
accounts for speaker placements, and compares rigid stands (lead-weighted,
spiked, metal frames) versus isolating stands (Sorbothane feet, flimsy stands,
sitting on a corrugated cardboard box). The verdict was that the isolating
stands were actually preferred over the rigid stands, in one test, but speaker
placement differences dominated over the stand types in the second test.
William Spencer
>I had presented my view in the proper set up of speakers. People
>argued with me, etc....... One poster was sold on his spikes. He had
>a situation where there was a basement under his listening room. He
>mentioned going down to the basement and remarking at how well he
>could hear the sound system from there. He was hearing the floor
>being driven by his speakers via the spikes coupling to the wood
>floor.
Sounds like this was me. I think this proves without question that spikes
potentially can make a difference in the midrange and possibly higher.
>It is my opinion that using spikes to couple to a wooden floor is a
>mistake. To a concrete floor= OK idea.
Yes, but what if the floor has carpet over it? Close call. At any rate, I
think that putting speakers directly on carpet is bad, or at least tickles my
toes too much.
>My assertion is that the speaker system should be either:
>1. Totally decoupled from the floor with a resilient mass. One that
>will absorb any cabinet vibrations.
>[2. partially decoupled into a mass]
Oops, deleted an extra line...In a practical case of partial decoupling and
no concrete, what gets through the resilence should not go into the carpet.
Or with stands, what gets into the stands should go into the floor.
My feeling is that spikes may be different than clamping the speaker to the
floor, but for most people it's just more convienient than clamping the speaker
to the floor. And on a concrete slab, it's the way to go.
Now for the dirty laundry...
Dick made two assertions regarding the possible causes of sound differences
due to coupling the speaker to the floor: 1.The cabinet doesn't move enough as
a unit to make a difference. 2.Coupling can not make a difference in reducing
the effect of panel resonances. These may be largely true, but not in extreme
cases.
Case 1 is a large dipole I made with 6 15" woofers. The base is 6" front to
back and it has a hinge in the middle. Without additional support, this thing
flapped like a flag flying in the wind, like up to 2". Someday maybe I'll
have to check out the difference with a sound level meter. I stiffened it up
with carriage bolts and a "crutch".
With question 2, consider a large tall woofer box with the woofer at the
bottom. With spikes (etc.) and a concrete floor, it is obvious that much of the
vibration will take the "short circuit" to the concrete.
Likewise, with a more typical speaker, panel vibrations are transmitted around
the panels, some of it passing through the bottom panel.
Adding coupling to an immovable surface is like adding a ground someplace
in a L-C circuit. You know it's going to change something. Depending on the
actual circuit, it may be in a minor branch of the circuit, it may cause
a null, or it could even cause a peak, especially if there's a bunch of stuff
added in series between the ground and the original circuit -- this is analogous
to the wooden floor case.
One case where I really thought I heard a difference was going from an
external spike to a permanently mounted one. I think the original one made
a loose connection to the speaker and caused a resonance or buzz.
BiLL S
Chris Christensen
>While I don't have data to prove it, I believe that spikes *improve*
>the coupling between the cabinet and the floor, rather than increasing
>the isolation. It is the enhanced transmission of mechanical energy
>to the body, through the floor, which gives the strong and real
>sense of more powerful bass.
What about the warming up of the midrange......
>This will be most noticeable on wooden floors. If this hypothesis is
>correct, then it should be possible to notice a much lesser improvement
>when using spikes on cement slab floors. Of course, that would imply
>trying to conduct some sort of experiment which controlled for subjective
>effects.
I don't know why I am getting into this discussion, again........
I had presented my view in the proper set up of speakers. People
argued with me, etc....... One poster was sold on his spikes. He had
a situation where there was a basement under his listening room. He
mentioned going down to the basement and remarking at how well he
could hear the sound system from there. He was hearing the floor
being driven by his speakers via the spikes coupling to the wood
floor.
It is my opinion that using spikes to couple to a wooden floor is a
mistake. To a concrete floor= OK idea.
My assertion is that the speaker system should be either:
1. Totally decoupled from the floor with a resilient mass. One that
will absorb any cabinet vibrations.
2. Coupled to a mass that will not transmit vibrations to the floor.
Practically, for larger free standing speakers, concrete is a pretty
good mass that doesn't "drive" well..... A couple a hundred pounds
should due. In fact, build your speaker stands with concrete! Couple
the cabinet to this mass in any way that is easy for you. Pointy feet,
lag bolts, foundation bolts, hot glue, etc.
If you have smaller speakers try using a dense foam rubber to support
the cabinet but isolate it from the shelf/stand.