"Dave Cook" wrote in message
On Oct 20, 7:21 pm, John Stone wrote:
Are you doing any level matching when you are
doing your comparisons?
No, but why can't I make one piece sound like the other
just by adjusting the volume? 
I'm trying to set up now for some level matched tests
with Room EQ Wizard and my Radio Shack SPL meter. If
I'm careful I think that should be able nail down
frequency response differences to within 0.1 dB or so.
Measurements in the acoustic domain are notoriously unstable.
I also tried measure the Vrms output from the amp with a voltmeter,
But mine does not seem to be accurate over 1kHz or so.
Most general use voltmeters are that way. Their major purpose in life is
measuring 50 or 60 Hz power.
Just use a 400 Hz test tone!