jj@rabbit.UUCP (08/02/83)
I quote someone at rochester: " Much closer effect to a phase shift between different frequencies (180 degrees was reported for some CD players) can be obtained by reversing the polarity of one speaker in the stereo pair. This is an exagerration, but the basic effect is the same - the sound appears "smeared" and originating everywhere, as the directionality is lost. " A phase shift between DIFFERENT FREQUENCIES is utterly, TOTALLY, and irrevocably UNRELATED to a phase shift BETWEEN CHANNELS. The perceptual effects of the two distortions are likewise utterly dissimilar. Good GRIEF! Good night! rabbit!<netnews has no bearing on reality, don't mail me>jj
ee461@rochester.UUCP (VLSI class) (08/03/83)
rabbit!jj didn't like my opinion on a phase shift in speakers and he/she wrote: "A phase shift between DIFFERENT FREQUENCIES is utterly, TOTALLY, and irrevocably UNRELATED to a phase shift BETWEEN CHANNELS. The perceptual effects of the two distortions are likewise utterly dissimilar. Good GRIEF! Good night!" OK, maybe I was wrong. Maybe rabbit!jj is a specialist to whom my uneducated theories sounded ignorant. But it would be nice if rabbit!jj could provide a better explanation for the effects of a phase shift instead of "good grief" and "good night". I've never claimed that the said effects are identical, but that they are similar. Also, I have some experimental evidence to support my claim. Some 3 years ago, when I build my own speakers (2-way, crossover at 1500 Hz) by a mistake I switched the polarity of the upper range driver in one of the speakers. It resulted in the usual weird sound. I switched the polarity of one of the speakers (now lower range was out of phase). Similar weird sound. I switched to mono - same thing. I disconnected one of the speakers. STILL unpleasant. The general character of what I could hear APPEARED TO ME to be similar in all cases. I know, that there is a quantitative difference between having one driver 180 degrees out of phase and a continuous phase shift for different frequencies as it occurs in the "normal" case. But qualitatively the situation is similar: different frequencies are transmitted with different phase shifts, and if there is a reason why the effects should be TOTALLY different, I'd like to know it. And if rabbit!jj could propose an easy home experiment to demonmstrate these differences, I would be more than happy. Until then, the best approximation I can think of is: Boost bass and attenuate treble in one channel. Do the opposite with the other channel (easily done with an equalizer). Switch to mono source. Place the speakers close each to other with the polarity of one speaker reversed. Try to enjoy the effects. This is what I meant in my previous article; sorry for not making it clear. Krzysztof Kozminski (ee461@rochester)