Someone at AVS came up with an idea of how the differences in the low frequency response was being created. They were preout signal related. When I boosted the preout levels of the 2 mains to match the other channels I was also unintentionally boosting the output to the subs below the sub crossover frequency. With stereo content this resulted in an increase of about 2db below 100hz, and was audible but subtle.
Here are the new graphs. They are virtually identical once the subs are out of the equation by removing it in the AVR settings.
R\L channels powered by
AVR. 1/12 octave averaged pink noise. 5db divisions. Towers ran full range, no sub.
R\L channels powered by
Seperate amplifier. 1/12 octave averaged pink noise. 5db divisions. Towers ran full range, no sub.
Matt, I still think it is genuinely possible for amps to make a difference in sound quality. I think it has more to do with the ability to play without distortion or tonal shift as spl increases. As for frequency response, both these amplifiers measure the same so far as the graphs show at a pink noise output of 75db.
