"Audio Empire" wrote in message
ScottW seems to think that audio is somehow a "special
case" and is more than just a complex waveform.
Its a common audiophile myth - they also deny that Fourier was right about
complex waves being logical decomposable into collections of sine waves.
I have not been able to convince him: 1) that amplifier
performance is pretty well understood, 2) that total D +
N plots tell the whole story about distortion and noise
levels with respect to signal, and 3) aggegate D + N
levels of about -115 dB below the rated output or more
are, for all intents and purposes, inaudible.
I strongly disagree with the -115 dB number. It is way too tough.
There are two numbers that seem to relate to audibility:
-100 dB or "The -100 dB rule" which says that any artifact that is 100 dB or
more down is unconditionally inaudible.
-80 dB, or "The -80 dB rule" which says that even when "only" -80 dB,
virtually all real-world aritfacts are inaudible.
Then there is also the -60 dB rule which represents the typical performance
of the best analog tape, LP playback and/or vacuum tube electronics, This is
often audible, but potentially tolerable and perhaps to some, euphonic.
So -100 dB is unconditionally audibly perfect, -80 dB is generally more than
good enough, and -60 dB is often audible, but might not sound all that bad.
The actual FR artifact (linear distortion) detection ability of the human
ear was provided by Clark in his ground-breaking (peer-reviewed) ABX
article, and is online at
http://home.provide.net/~djcarlst/abx_crit.gif .
This chart shows the size and center frequency of FR artifacts that are
unconditionally inaudible. Typical JND's are about 3 times what it shows.
The chart has a built-in safety factor of 3:1 or so.
The ear is much more tolerant of linear distortion than nonlinear
distortion. The unconditional inaudible FR variation of 0.1 dB amounts to
being about 1% distortion. Typical variations on the order of 1 dB in the
midrange are audible, which amounts to 10% distortion.
For comparison there are essentually no speakers that are free of audible FR
artifacts, and essentually none that have all nonlinear distortion better
than 40 dB down over a reasonble range of frequencies and SPLs. Under ideal
conditions, some speakers have most artifacts down close to -60 dB over a
fairly limited and incomplete range of frequencies.
There is a belief of some audiophiles that speaker distortion is somehow
more euphonic than the distortion in electronics, and this is generally not
true. Analog tape probably has a combination of nonlinear and linear
distortion that is the closest to euphonic of all common audio situations.