"Bob-Stanton" wrote in message
om
"Arny Krueger" wrote in message news:Oy-


I don't see clear causality here because the second active filter was
causing several changes. It was effectively upping the tweeter
crossover from 4th order to 8th order. Furthermore, depending on the
impedance curves of the tweeters, the 4th order passive filter might
not have always produced the expected filter characteristic in terms
of voltage at the input terminals of the tweeter. It might provide a
lot less cutoff than expected.

Actually, I did take out the first filter, when I inserted the second
(active) filter in front of the amplifier. So, the response remained
rolled off by the same 24dB/octave.

Providing that the passive filter had the identical same response, which I
will doubt until measurements are shown.

---broadband sound------ High pass filter------CD
player------amplifier----- full range speaker

The above not really necessary, since we are looking for a *change* in
audible distortion.

It is necessary because we're looking for a change that we can attribute to
some UUT, either amplifier, CD player or both.

Also, I doubt that the CD-player contributes very
much distortion.

I doubt that either a good amp or a CD player contributes much distortion
since I've done the experiment outlined above with several amps including an
OEM car audio system.

If the amount of audible distortion is dependent on amplifier volume
control settings, and actual volume levels remain high enough that
Fletcher-Munson effects remain constant, then the distortion is in
the amplifier.

That is why I suggested an using and (optional) L-pad in front of the
tweeter. It's a little bit more work, but the level out of the tweeter
can be kept constant as the volume of the amplifier increases.

The L-pad changes the impedance of the load on the amplifier, greatly.

This turns out to be a very sensitive test for amplifier clipping.
With 2 KHz and higher high pass filters, it's easy to surprise
yourself by clipping the amplifier at rated power, and yet have
sound levels that don't seem to be that high.

That is right. The change in sound quality from the tweeter is
probably caused by clipping. This test shows what the amplifier can
put out, before clipping. However, you might be surprised to find that
some amplifiers don't put out full rated power before distortion is
audible.

There are some issues related to measuring peak power versus average power.

Clipping is not the only thing that could cause this distortion. TIM
could cause it as well. (You say, modern amplifiers don't have TIM?
Good, than they will pass the test with no problem.)

No, I say that TIM is an obscure way to talk about high frequency nonlinear
distortion.