William Sommerwerck wrote:

At the last Stereophile writers' meeting I attended, at least 15 years ago, John
Atkinson asked an intelligent question. To wit...

"Why is it that some mounts are supposed to isolate the amp/CD player, etc, from
the surface they're on, while others couple it tightly to the surface (cones, in
particular), yet both approaches claim improved sound?"

I suggested that one way to find out would be to play an impulse from a CD
through a speaker in front of the player. (A similar experiment to test
amplifiers could be done with a pulse generator feeding the amp.) You could then
look at the pulse's spectrum and decay (at the player's or amp's output) using a
variety of isolation devices, no isolation at all, and with no speaker at all
(as a reference). This should show whether CD players, etc, are meaningfully
microphonic, and whether isolation devices have any effect.

John thought that was a good idea. Then he said the thing that forever made me
lose respect for his "understanding" of science.

"But what if there's no difference between the isolating devices?"

God, what will those who advertise such items in the
magazine think, and worse yet, do?

In case this isn't clear... You don't assume the result before performing an
experiment. Indeed, it's often better to perform an experiment simply to see
what happens, rather than trying to "prove" or "disprove" something.

I doubt that John ever performed the experiment. I am guilty, too, of failing to
follow through on subjective observations with controlled experiments.

I forgive you, and, believe it or not, forgive John, too.

Incidentally, I wrote an article for Stereo Review Magazine
about three decades back where I did pretty much as you
indicated, but did so with an LP record player instead of a
CD player, with the human ears as the evaluation tool.

I even showed how someone could use their record player to
rather carefully evaluate the feedback. The player
essentially would behave as a microphone that would clearly
determine just how much of an audible problem feedback would
be. Often, the feedback was fairly strong, but not always,
depending upon how well isolated the turntable would be from
the mounting base. I even evaluated how audible feedback
from footfalls near a record player would be.

With CD players, I would hazard that the only artifact that
would possibly be audible would be gross mistracking. If
that did not occur, probably the feedback would be
inaudible.

However, like you I have not done that experiment.

Howard Ferstler