"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.


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


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.

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.

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

Bob Stanton