I have analyzed my Hafler 9505. The Hafler used is flat from 0 to
300Khz +/- almost nothing on both channels (showing no real measurable
distortion). The signal going in to the Hafler via signal
generator appears to be completely unaltered when measuring it as output
at varying frequencies/gain levels..
While I didn't analyze the signal going in/out of the PASS, I will
assume that it was up to spec. Having made that assumption the question
is as follows.
How is it possible that two amplifiers could reproduce the signal identically,
and still sound different?
What element, if not apparent in the output signal, accounts for better
soundstage in the PASS?
What element accounts for the "Punch" demonstrated by Hafler?
Any answers you could provide would be greatly appreciated. Feel free
to get as technical as you need. My email is buf...@home.com
Thank you for your time,
-----------== Posted via Deja News, The Discussion Network ==----------
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After this experience, I made the conclusion that for an amplifier and
for any audio equipment a listening test is much more important than
buf...@home.com wrote in message <7g5o07$ua6$1...@nnrp1.dejanews.com>...
>I am an audio enthusiast on search for an amplifier. My current
>amplifier is the Hafler 9505. I recently auditioned the Pass Aleph2 and
>the X (600) series amplifier in an all-PASS system. Both of the
>amplifiers sounded very good. Upon comparing the Pass Aleph2 to my
>Hafler, I noticed that the PASS had a superior soundstage ... and
>surprisingly to me, a bit more bass -- although the Aleph certainly
>lacked "SLAM" (impact) when compared to the Hafler.
>I have analyzed my Hafler 9505. The Hafler used is flat from 0 to 300Khz
>+/- almost nothing on both channels (showing no real measurable
>distortion). The signal going in to the Hafler via signal generator
>appears to be completely unaltered when measuring it as output at varying
>While I didn't analyze the signal going in/out of the PASS, I will assume
>that it was up to spec. Having made that assumption the question is as
>How is it possible that two amplifiers could reproduce the signal
>identically, and still sound different?
Obviously *SOMETHING* is not identical about the two amplifiers.
>What element, if not apparent in the output signal, accounts for better
>soundstage in the PASS?
>What element accounts for the "Punch" demonstrated by Hafler?
>Any answers you could provide would be greatly appreciated. Feel free to
>get as technical as you need. My email is buf...@home.com
Too many assume that the measurements can somehow predict how a listening
jury will rank a group of amplifiers. Unfortunately, we don't know
everything about how our ears work, and the measurements are too simple.
Go to your local library and read through the JAES (Journal of the Audio
Engineering Society) to get a feel for the struggle to concoct a series of
measurements that can predict which amplifier will sound better.
There is a group of engineers who feel that if one hears a difference
between two quality amplifiers (they can't put any numbers on what
"quality" means) there is something wrong with the demonstration.
In my own exerience some of the worst amplifiers I've heard were designed
with the tightest technical specs. They will have low distortion, good
heatsinking, wide bandwidth, lots of power, this circuit and that, and on
and on, but still not be very pleasant sounding.
As we learn more, we may find a set of numbers that will predict which
model sounds best, but we are not there yet.
nite...@voicenet.com (Barry Mann)
The 'impact' of a bass note depends partly on the control of the woofer,
to prevent its natural resonance in the cabinet from mixing with the
source signal and producing intermods that muddy the sound. A high
damping factor is important here.
High instantaneous power allows a brief undistorted bass signal several
dB higher than the rated power, and also sufficient power in the initial
transient of the 'punch', which has much higher-frequency content.
Measuring the power bandwidth under continuous-sine-wave conditions will
not tell you anything about these factors.
> MY QUESTION.
> While I didn't analyze the signal going in/out of the PASS, I will
> assume that it was up to spec. Having made that assumption the question
> is as follows.
> How is it possible that two amplifiers could reproduce the signal identically,
> and still sound different?
Actually, no. As has been shown numerous times in this forum, the
damping factor of an amplifier is all but meaningless. The DC resistance
of the loudspeaker is, by far, the dominant loss in the system. The
source resistance of the amplifier is orders of magnitude less in
most cases, making it an unimportant factor in the performance of the
> Actually, no. As has been shown numerous times in this forum, the
> damping factor of an amplifier is all but meaningless. The DC resistance
> of the loudspeaker is, by far, the dominant loss in the system. The
> source resistance of the amplifier is orders of magnitude less in
> most cases, making it an unimportant factor in the performance of the
This post sounds confused. Speaker system mechanical resonances in fact
appear as an emf source that sees the speaker impedance in parallel with the
amplifier source virtual impedance as the load. Since the amplifier source
impedance is indeed much smaller than the speaker impedance, the latter is
almost insignificant. In fact, an amplifier with a damping factor of 50 will
sink twice the current of one with a damping factor of 25, and therefore
dissipate four times the resonant energy.
If the speaker system is well damped mechanically and thus produces little
induced emf when stimulated by the input signal, then the damping factor has
little effect. In an underdamped system, however, you should notice the
improved bass control afforded by a large damping factor. Since the source
impedance of a good amplifier is so low, poor speaker connections or
resistive wires totalling 0.1 Ohms can halve the effective damping factor,
say from 50 at 4 Ohms to 25. Therefore, with an underdamped speaker system,
this also becomes a significant issue.
No, you are confused. Your analysis completely ignores the fact that it is
the TOTAL effective series resistance that is responsible for dissipating
the energy, NOT just that of the amplifier. So, given a hypothetical 8 ohm
speaker with 7 ohms of DC resistance, that total resistance is 7+8/25 or
7.32 ohms for the damping factor of 25 case, compared to 7+8/50 or 7.16
ohms for the damping factor of 50 case.
NOW make your comparison: dissipatying the energy in 7.32 vs 7.16 ohms. It
is no longer the 2:1 difference you claimed: it's more like all of 2%.
>If the speaker system is well damped mechanically and thus produces little
>induced emf when stimulated by the input signal, then the damping factor has
>little effect. In an underdamped system, however, you should notice the
>improved bass control afforded by a large damping factor. Since the source
>impedance of a good amplifier is so low, poor speaker connections or
>resistive wires totalling 0.1 Ohms can halve the effective damping factor,
>say from 50 at 4 Ohms to 25. Therefore, with an underdamped speaker system,
>this also becomes a significant issue.
Every single analysis that depends upon such large differences in damping
factor simply ignores the fact that there is ALWAYS that DC resistance in
the voice coil: it is ALWAYS there REGARDLESS of what's in the amplifier
and is, in the vast majority of cases, THE dominant series electrical loss
element of the entire system. Your analysis is similarily flawed: there
simply is NOT a 2:1 difference in the loss in the system: the resistance
of the amplifier and speaker leads and crossover are NOT the only such
resistance nor, in most cases are they even the most important ones.
Until you can show that these resistances are the greatest share of the
total series losses, any claims you might make about damping factor are
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| DPi...@world.std.com |
First, the assertion:
In article <7go6da$b8q$1...@nnrp1.dejanews.com>, <aq...@lafn.org> wrote:
>> Actually, no. As has been shown numerous times in this forum, the
>> damping factor of an amplifier is all but meaningless. The DC resistance
>> of the loudspeaker is, by far, the dominant loss in the system.
>This post sounds confused. Speaker system mechanical resonances in fact
>appear as an emf source that sees the speaker impedance in parallel with the
>amplifier source virtual impedance as the load. Since the amplifier source
>impedance is indeed much smaller than the speaker impedance, the latter is
>almost insignificant. In fact, an amplifier with a damping factor of 50 will
>sink twice the current of one with a damping factor of 25, and therefore
>dissipate four times the resonant energy.
DAMPING FACTOR: EFFECTS ON SYSTEM RESPONSE
A TECHNICAL ANALYSIS
Professional Audio Development
Much ballyhoo surrounds the concept of "damping factor." it's been
suggested that it accounts for the alleged "dramatic differences" in
sound between tube and solid state amplifiers. The claim is made
(and partially cloaked in some physical reality) that a low source
resistance aids in controlling the motion of the cone at resonance
and elsewhere, for example:
"reducing the output impedance of an amplifier and
thereby increasing its damping factor will draw more
energy from the loudspeaker driver as it is oscillating
under its own inertial power." 
This is certainly true, to a point. But many of the claims made,
especially for the need for triple-digit damping factors, are not
based in any reality, be it theoretical, engineering, or acoustical.
This same person even suggested:
"a damping factor of 5, ..., GROSSLY changes the time/
amplitude envelope of bass notes, for instance. ... the
note will start sluggishly and continue to increase in
volume for a considerable amount of time, perhaps a
second and a half."
Instead of unbridled hyperbole, there have been attempts at a
reasoned justification for damping factor. Witness a recent
"Since the amplifier source impedance is indeed much
smaller than the speaker impedance, the latter is almost
insignificant. In fact, an amplifier with a damping factor
of 50 will sink twice the current of one with a damping
factor of 25, and therefore dissipate four times the
resonant energy." 
As intuitive as this analysis might seem, it is quite flawed since,
as we will see, it simply ignores the one major loss factor in the
entire system, throwing it out the window as if the single most
important controlling element over cone motion had no real
2 DAMPING FACTOR: A SUMMARY
What is damping factor? Simply stated, it is the ratio between the
nominal load impedance (typically 8 ohms) and the source impedance
of the amplifier. Note that all modern amplifiers (with some
extremely rare exceptions) are, essentially, voltage sources, whose
output impedance is very low. That means their output voltage is
independent, over a wide range, of load impedance.
Many manufacturers trumpet their high damping factors (some claim
figures in the hundreds or thousands) as a figure of some
importance, hinting strongly that those amplifiers with lower
damping factors are decidedly inferior as a result. Historically,
this started in the late '60's and early '70's with the widespread
availability of solid state output stages in amplifiers, where the
effects of high plate resistance and output transformer windings
traditionally found in tube amplifiers could be avoided.
Is damping factor important? Maybe. We'll set out to do an analysis
of what effect damping factor has on what most proponents claim is
the most significant property: controlling the motion of the speaker
where it is at its highest, resonance.
The subject of damping factor and its effects on loudspeaker
response is not some black art or magic science, or even excessively
complex as to prevent its unserstanding by anyone with a reasonable
grasp of high-school level math. It has been exhaustively dealt with
by Thiele , Small  and many others decades ago.
3 SYSTEM Q AND DAMPING FACTOR
The definitive measurement of such motion is a concept called Q.
Technically, it is the ratio of the motional impedance to losses at
resonance. Another, completely equivalent view is that Q is the
ratio between the amount of energy stored in the system vs the
energy dissipated by losses.
It is a figure of merit that is intimately connected to the response
of the system in both the frequency and the time domains. A loud-
speaker system's response at cutoff is determined by the system's
total Q, designated Qtc, and represents the total resistive losses
in the system.
Two loss components make up Qtc: the combined mechanical and
acoustical losses, designated by Qmc, and the electrical losses,
designated by Qec. The total Qtc is related to each of these
components as follows:
Qmc * Qec
Qtc = --------- [Eq 1]
Qmc + Qec
Qmc is determined by the losses in the driver suspension, absorption
losses in the enclosure, leakage losses, and so on. Qec is
determined by the combination of the electrical resistance from the
DC resistance of the voice coil winding, lead resistance, crossover
components, and amplifier source resistance. Thus, it is the
electrical Q, Qec, that is affected by the amplifier source
resistance, and thus damping factor.
Qec itself is a measure of, simply, the ratio of the energy stored
in the moving system to the energy dissipated electrically by the
losses in the system, that is, in the resistances in the system. The
energy stored in the moving system, the kinetic energy, is dependent
upon the amount of mass and the velocity.
In the context of a speaker, the Qe is (from Small):
Qec = 2 pi Fc Mmc Re / B l [Eq 2]
where Fc is the resonant frequency of the system, Mac is the
equivalent moving mass of the system, and Re is the DC resistance of
the voice coil (and this assumes 0 source impedance or "infinite"
damping factor). Further, B represents the magnetic flux density in
the gap and l the length of wire in the magnetic field. (We will
assume that we are using the same driver for all considerations
here, thus, Fc, Mmc B and l remain the same as well.)
The effect of source resistance on Qec is simple and straight-
forward. From Small again :
Re + Rs
Qec' = Qec --------- [Eq 3]
where Qec' is the new electrical Q with the effect of source
resistance, Qec is the electrical Q assuming 0 source resistance
(infinite damping factor), Re is the voice coil DC resistance, and
Rs is the combined source resistance.
Re + Rs
--------- [Eq 4]
comes from the fact that Re is built into the original derivation
for Qec includes Re in it. The correction simply calculates the
incremental increase in Qe with the incremental increase in the
total electrical resistance. Reconciling [Eq 4] with [Eq 2], we see
Qec = 2 pi Fc Mmc (Re+Rs) / B l [Eq 6]
Thus it becomes obvious that the electrical Q of the speaker or,
more generally, the electrical damping of the speaker, is NOT
dependent upon the source resistance Rs alone (as the proponents of
damping factor erroneously claim), but on the TOTAL series
resistance seen by the driver, including the DC resistance of the
voice coil, Re. This mistake, as commonly as it is made, the the
fatal flaw in the entire damping factor argument.
It's very important at this juncture to note two points. First, in
nearly every loudspeaker system, and certainly in every loudspeaker
system that has any pretenses of high-fidelity, the majority of the
losses are electrical in nature, usually by a factor of 3 to 1 or
greater. Secondly, of those electrical losses, the largest part, by
far, is the DC resistance of the voice coil.
Now, once we know the new Qec' due to non-zero source resistances,
we can then recalculate the total system Q as needed using [Eq 3],
The effect of the total Q on response at resonance is also fairly
straightforward. Again, from Small , we find:
Gh(max) = sqrt(-------------) [Eq 7]
Qtc - 0.25
This is valid for Qtc values greater than 0.707. Below that, the
system response is overdamped and there is no response peak.
We can also calculated how long it takes for the system to damp
itself out under these various conditions. The scope of this article
precludes a detailed description of the method, but the figures
we'll look at later on are based on both simulations and
measurements of real systems, and the resulting decay times are
based on well-established principles of the audibility of
reverberation times at the frequencies of interest.
4 PRACTICAL EFFECTS OF DAMPING FACTOR ON SYSTEM RESPONSE
With this information in hand, we can now set out to examine what
the exact effect of source resistance and damping factor are on real
loudspeaker systems. Let's take an example of a closed-box, acoustic
suspension system, once that has been optimized for an amplifier
with an infinite damping factor. This system, let's say, has a
system resonance of 40 Hz and a system Qtc of 0.707 which leads to a
maximally flat response with no peak at system resonance. The
mechanical Qmc (i.e. the mechanical contributions to system losses
and thus damping) of such a system is typically about 3, we'll take
that for our model.
Rearranging [Eq 1] to derive the electrical Q of the system:
Qtc * Qmc
Qec = --------- [Eq 8]
Qtc - Qmc
we find that the electrical Q of the system, with an infinite
damping factor, is 0.925.
The DC resistance of the voice coil is typical at about 6.5 ohms.
Let's generate a table that shows the effects of progressively lower
damping factors on the system performance:
Damping Rs Qec' Qtc' Gh(max) Decay
inf. 0 ohms 0.925 0.707 0.0 dB 0.04 sec
2000 0.004 0.926 0.707 0.0 0.04
1000 0.008 0.926 0.708 0.0 0.04
500 0.016 0.927 0.708 0.0001 0.04
200 0.04 0.931 0.71 0.0004 0.04
100 0.08 0.936 0.714 0.0015 0.04
50 0.16 0.948 0.72 0.0058 0.04
20 0.4 0.982 0.74 0.033 0.041
10 0.8 1.04 0.77 0.11 0.043
5 1.6 1.15 0.83 0.35 0.047
2 4 1.49 0.99 1.24 0.056
1 8 2.06 1.22 2.54 0.069
The first column is the damping factor using a nominal 8 ohm load.
The second is the effective amplifier source resistance that yields
that damping factor. The third column is the resulting Qec' caused
by the non-zero source resistance, the fourth is the new total
system Qtc' that results. The fifth column is the resulting peak
that is the direct result of the loss of damping control because of
the non- zero source resistance, and the last column is the decay
time to below audibility in seconds.
Several things are apparent from this table. First and foremost, any
notion of severe overhang or extended "time amplitude envelopes)
resulting from low damping factors simple does not exist. We see, at
most, a doubling of decay time (this doubling is true no matter WHAT
criteria is selected for decay time). The figure we see here of 70
milliseconds is well over an order of magnitude lower than that
suggested by one person, and this represents what I think we all
agree is an absolute worst-case scenario of a damping factor of 1.
Secondly, the effects of this loss of damping on system frequency
response is non-existent in most cases, and minimal in all but the
worst case scenario. If we select a criteria that 0.1 dB is the
absolute best in terms of the audibility of such a peak (and this is
probably overly optimistic by at least a factor of 2 to 5), then the
data in the table suggests that ANY damping factor over 10 is going
to result in inaudible differences between such a damping factor
and one equal to infinity. It's highly doubtful that a response peak
of 1/3 dB is going to be identifiable reliably, thus extending the
limit another factor of two lower to a damping factor of 5.
Further, we simply do not observe the "factor-of-four" increase in
energy dissipation with a factor of two reduction in source
resistance as claimed in . The statement that it's all about
energy dissipation is quite correct: remember that what damping is
doing is removing energy from a resonant system, and that the
measure of damping is Q, the ratio of energy stored to energy
dissipated. Look, for example, at the difference in Qt between a
damping factor of 50 and 20: the actual difference in the energy
dissipated is less than 3%. According to the theory expounded in
, the difference in energy dissipation should be around a factor
All this is well and good, but the argument suggesting that these
minute changes may be audible suffers from even more fatal flaws.
The differences that we see in Q figures up to the point where the
damping factor is less than 10 are far less than the variations seen
in normal driver-to-driver parameters in single-lot productions.
Even those manufacturers who deliberately sort and match drivers are
not likely to match a Qt figure to better than 5%, and those numbers
will swamp any differences in damping factor greater than 20.
It is well known that the performance of drivers and systems is
dependent upon temperature, humidity and barometric pressure, and
those environ- mental variables will introduce performance changes
on the order of those presented by damping factors of 20 or less.
And we have completely ignored the effects presented by the
crossover and lead resistances, which will be a constant in any of
these figures, and further diminish the effects of non-zero source
There may be audible differences that are caused by non-zero source
resistance. However, this analysis and any mode of measurement and
listening demonstrates conclusively that it is not due to the
changes in damping the motion of the cone at the point where it's at
it's most uncontrolled: system resonances. We have not looked at the
frequency- dependent attenuative effects of the source resistance,
but that's not what the strident claims are about.
Rather, the people advocating the importance of high damping factors
must look elsewhere for a culprit: motion control at resonance
simply fails utterly to explain the claimed differences.
 James Kraft, reply to "Amplifier Damping Factor,
Another Useless Spec," rec.audio.high-end article
2rcccn$u...@introl.introl.com, 24 May 1994.
 Steve (aq...@lafn.org), reply to "How can 2 amps
sound so different?," rec.audio.tech article
7go6da$b8q$1...@nnrp1.dejanews.com, 04 May 1999.
 A. Neville Thiele, "Loudspeakers in Vented Boxes,"
Proc. IRE Australia, 1961 Aug., reprinted J. Audio
Eng. Soc., 1971 May and June.
 Richard H. Small, "Closed-Box Loudspeaker Systems,"
J. Audio Eng. Soc., Part I: "Analysis," 1972 Dec,
Part II, "Synthesis," 1973 Jan/Feb.
Copyright 1994, 1995, 1998 and 1999 by Dick Pierce.
Permission given for one-time no-charge electronic
distribution with subsequent followups.
All other rights reserved.
I've been wondering about this. Isn't the the DC resistance of the voice coil
in parallel to the e.m.f. that results from uncontrolled cone motion, while the
resistance of the speaker wire and connectors and the output impedance fo the
amplifier are in series with it?
No, the voice coil resistance is quite definitely in series with the
resonant portion of the impedance, NOT in parallel with it.
Look at the implications of your assertion: the electrical equivalent of
the resonant system is that of a parallel RLC resonant circuit, consisting
of an inductive equivalent of the system compliance, a capacitive
equivalent of the moving mass, and a resistive equivalent of the
mechanical losses of the system:
| | |
Lces Cmes Res
| | |
Analyze the behaviour of this circuit: at resonance, the impedance is
determined by the parallel resonant impedance of the inductor and
capacitor and the resistor for the mechnical loss, so the impedance at
resonance peaks at a high determined by Res (might be equivalent to 20-100
ohms, depending upon suspension losses).
However, what's the impedance of this circuit at very low or very high
frequencies? Well, it approaches 0, because of the shunting effect of Lces
at low frequencies and that of Cmes at high.
Put the DC resistance, RE, of the voice coil in parallel with this: you
now have a system whose impedance at DC and at very high frequencies is a
dead short, while at reesonance is equal to the DC resistance of the voice
coil. This is, quite clearly, completely different from what speakers
Instead, put the DC resistance in series: now you have a system whose
resistance at DC is the DC resistance of the voice coil (duh!), and whose
maximum at resonance is determined by the mechanical losses of tyhe
suspension, just like real speakers.
Look at it in another way: ALL the current that flows through the voice
coil, whether it originates from the amplifier for from the "emf" MUST
flow through that DC resistance: to do so, the DC resistance MUST be in
series with the entire rest of the system.
So say I, so says Mr. Thevenin.
Of course!!! Well, I'm convinced now. So it looks like any REAL "damping
factor" that is beyond some fairly small number (certainly less than 50) has no
> 6 CONCLUSIONS
> There may be audible differences that are caused by non-zero source
> resistance. However, this analysis and any mode of measurement and
> listening demonstrates conclusively that it is not due to the
> changes in damping the motion of the cone at the point where it's at
> it's most uncontrolled: system resonances. We have not looked at the
> frequency- dependent attenuative effects of the source resistance,
> but that's not what the strident claims are about.
That may not be what people are claming to be the reason, but the
voltage division effects are definitely audible in amps with _really_
low DFs, like zero-feedback single-ended triodes. This effect far
outweighs the actual system damping. That's also part of what gives
them the (subjectively) warm, pleasing sound quality - although few
would admit it, because that means the frequency response of the amp
isn't flat. Measurably not flat, even with my bear skins and stone
> Rather, the people advocating the importance of high damping factors
> must look elsewhere for a culprit: motion control at resonance
> simply fails utterly to explain the claimed differences.
By "elsewhere" I would suggest things like the amount of negative
feedback and output current capability. Both are well-correlated to
output impedance and therefore the damping factor. An amp with a
large amount of NF can have a vanishingly low low frequency
distortion number, and this may be interpreted by some listeners
as 'better bass'. Has nothing to do with the output impedance or
cone motion control, but rather the _amount of distortion_. But
NF can cause other problems, and an amp that has a DF of 2000
at 20 Hz might still sound like sh*t to some listeners when the
feedback 'misbehaves' on some program material (not sine waves).
High current capability amps have either lots of parallel output
transistors, really stiff supply rails, or both. Both reduce
IM distortion in the output signal, ESPECIALLY if the amp is
near clipping or actually clipping. Again, it's a signal quality
issue, not having anything to do with system damping. Put a
1/2 ohm resistior in series with a big monster amp with a DF of
1000 and the bass slam would likely be just as good, because
it's not the damping factor that's responsible.
Note that I am NOT arguing with Dick here, but rather pointing
out other things which are responsible for perceived differences
in bass quality between amps. The high damping factor may be
correlated, but it's just incidental.
I think is has to do with the demonstrable fact that if you took two
otherwise identical amps, even two PASS amps, that differed ONLY in the
amount of voltage gain, say as little as 0.25 dB or even less, they WILL
sound different to almost everyone, but NOT in a way that would suggest
that one is louder than the other (often, listeners will characterize the
slightly louder one as being "more detailed", "fuller", "warmer" and all
sorts of things, but almost never "louder"). 0.25 dB corresponds to a
voltage gain difference of only 3%, a TINY variation.
Unless one can show that such differences were controlled in any tests,
how can ANYONE be sure that the differences they heard were not due to
simple effects such as gain differences, fallible audio memory, or any one
of many irrelevant factors?
But, since all speakers have much higher distortion figures than
0.001%, more like >0.1% in good cases, and that is at least 100x
more distortion than the amp, maybe more like 1,000x more, forget
about the distortion figure on the receiver entirely.
Makes sense to me.
> Makes sense to me.
You assume that all distortion is of the same kind, which is far from
the truth. For example, I have a high-end hifi ending in Quad ELSs,
one of the lowest distortion spekars available. In the bath I
sometimes listen to a small cheap pocket transistor radio whose FM
decoder, amplifier, and speaker, all contribute orders of magnitude
more distortion than is present in my hifi. Neverthless, sometimes I
hear a music broadcast on the pocket tranny speaker which I instantly
identify as being of quite unusually ggod audio quality, and sometimes
I get out of the bath to switch on the hifi to record it. I have not
often been wrong in the judgment of quality I formed via the tiny
As another instance, when I was building some small speakers for a
semi-portable (luggable) radio which used small single drivers of
about 4" diameter, I experimentally tried them out on the various
different amplifiers I had at the time. I was surprised to discover
that even on these cheap low quality speakers some of the differences
between an extremely good and a superlative amplifier were still
These are not an uncommon observations, and proves that different
kinds of distortion are neither necessarily additive nor masking.
The problem is that we do not listen to waveforms, we listen to music
played (so it seems) by a variety of different instruments). This is a
complex perceptual construct which our brains devise using many
different features of the waveform in many different ways. Some of the
features used are gross and very resistant to distortion, such as
left-right volume differences, and some of them, such as high
frequency phase differences, are very small and easily degraded by
small amounts of certain kinds of distortion.
Chris Malcolm c...@dai.ed.ac.uk +44 (0)131 650 3085
School of Artificial Intelligence, Division of Informatics
Edinburgh University, 5 Forrest Hill, Edinburgh, EH1 2QL, UK
<http://www.dai.ed.ac.uk/daidb/people/homes/cam/> DoD #205