RobHolt
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Reading the 30 page (!) preamble to a 1976 book containing in depth reviews on receivers by the late Angus McKenzie and it made some interesting points.
The mid to late 70s saw companies in a spec war to produce the lowest THD, but McKenzie points out that several percent of THD, particularly at the frequency extremes is sonically pretty benign and often passes undetected. However, much smaller amounts of IMD are subjectively far more objectionable.
This was interesting since in the 70s, many designs routinely produce IMD at 0.1-0.5% even for quite expensive models of amplifier. McKenzie found that invariably his blind listening panel results when reviewing would tally with the nature of IMD produced by the amplifiers or receivers on test. The same correlation could not be made for varying degrees of THD, and the case was made that IMD consists of artefacts not harmonically related to the original signal, unlike THD and that this is far more sonically irritating.
I'll scan and upload the piece later but it does make a strong case that many manufacturers spent an awful lot of time looking at the wrong numbers, and perhaps still do.
Today it's rare to find SS equipment with audible distortion of any kind, but certainly loudspeakers still produce very audible distortions, and especially IMD.
The mid to late 70s saw companies in a spec war to produce the lowest THD, but McKenzie points out that several percent of THD, particularly at the frequency extremes is sonically pretty benign and often passes undetected. However, much smaller amounts of IMD are subjectively far more objectionable.
This was interesting since in the 70s, many designs routinely produce IMD at 0.1-0.5% even for quite expensive models of amplifier. McKenzie found that invariably his blind listening panel results when reviewing would tally with the nature of IMD produced by the amplifiers or receivers on test. The same correlation could not be made for varying degrees of THD, and the case was made that IMD consists of artefacts not harmonically related to the original signal, unlike THD and that this is far more sonically irritating.
I'll scan and upload the piece later but it does make a strong case that many manufacturers spent an awful lot of time looking at the wrong numbers, and perhaps still do.
Today it's rare to find SS equipment with audible distortion of any kind, but certainly loudspeakers still produce very audible distortions, and especially IMD.
