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On Dec 26, 11:57 am, Sonnova wrote:
Output impedance is one of many criteria. Mostly,
it affects damping factor for the loudspeakers.

Mostly, it does not at all.

The way I understand it is If a dynamic speaker is
looking down it's cable into the output stage of an
amplifier and sees, what is in essence, a dead
short, the cone will stop instantly when the signal
stops, because of the back EMF being generated
by the shorted voice coil in the speaker's magnetic
field (try this experiment: Get a raw driver and flex
the cone by hand at the dust cap. Then connect the
terminals of the speaker together with a jumper and
flex the cone again. Notice how much more difficult
the cone is to move this time.

Unless you're moving the cone VERY fast, you're not
going to see any difference.

Now, try the experiment REALISTICALLY: Try doing
it and trying to sense the difference between a 0.4 ohm
resistor across the terminals vs a 0.1 ohm resistor
across the terminals.

That's the phenomenon behind regenerative
dampening)

There is no "regenerative damping." It's just damping.

But even this is an oversimplification.

Yes, it is an oversimplification to the point of being
wrong.

In reality, most speaker voice coils are looking into
an inductor in the crossover and the resistance of
the speaker cable before it sees the output stage,

And, in oversimplifying, you neglected the fact that
the single LARGEST resistance is ALWAYS there,
and that's the DC resistance of the voice coil. The
inductor might add a fraction of an ohm, same with
the leads, but the DC resistance of a typical niminal
8 ohm driver is in the realm of 6-7.5 ohms, and
THAT resistance completely dominates all others,
including the amplifier's output resistance, and it
is the voice coil resistance that essentially determines
the damping of the system.

so its anybody's guess how much a low output
impedance actually affects the overall result.

Actually, it's not guesswork at all. The series resistance
the voice coil dominates, and unless the other series
resistances are pathologically large and the so-called
damping factor is larger than 10-20, the amplifier's
output resistance will have NO appreciable effect on
the damping of the system.

Frankly, I think that the sound of an amplifier is more
a result of the complex load presented by the speaker
system that it's driving than the speaker's sound is
influenced by the amplifier.

That may be the case, but, again, it's something that
can be determined. If we have an amplifier whose
damping factor is "low" by contemporary standards,
say, 20 at 8 ohms, and we connect it to a speaker
whose impedance varies from 6 to 30 ohms. The
result is that the voltage at the speaker terminals
varies by 0.44 db between the minimum and maximum
impedance.

Now, get yourself an amplifier with an alledged damping
factor of, oh. 200. The resulting error is now on the order
of 0.05 dB. Do you think that you can hear the difference
resulting from a smooth change in broadband frequency
response of about 0.4 dB in a room with dynamically
changing music?