[Amps] IMD

[Jim Brown]

On 1/12/2012 3:18 PM, Fuqua, Bill L wrote:
> The human ear does not hear waveform or phase shifts. In fact it a bunch of overlapping narrow bandpass filters that only respond to
> amplitudes at their resonant frequencies.

Not true!  RELATIVE phase differences are QUITE audible, and they made 
that K2 RX pretty awful to listen to. We may not IDENTIFY a particular 
nastiness of sound quality to non-uniform phase response, but that is a 
matter of ear training, not reality.  One thing we learned to do is to 
listen to the distortion output of a distortion analyzer so that we know 
what each form of distortion sounds like -- harmonic distortion, IMD, 
tracking distortion in vinyl recordings, scrape flutter in analog tape, 
and so on. Once the ear/brain has heard it and identified it, it's quite 
obvious. Phase distortion, polarity errors, polarity errors between 
multi-way loudspeakers, and time misalignment between parts of a 
loudspeaker system are quite audible once you have learned to identify 
them. They all contribute to our being able to tell the difference 
between the actual sound and the reproduction.

73, Jim K9YC