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Path: utzoo!linus!decvax!harpo!seismo!rochester!ee461
From: ee461@rochester.UUCP (VLSI class)
Newsgroups: net.audio
Subject: Re: Superstition (effects of a speaker phase shift revisited)
Message-ID: <2461@rochester.UUCP>
Date: Tue, 2-Aug-83 19:20:45 EDT
Article-I.D.: rocheste.2461
Posted: Tue Aug  2 19:20:45 1983
Date-Received: Wed, 3-Aug-83 04:59:00 EDT
References: <1744@rabbit.UUCP>
Organization: U. of Rochester, CS Dept.
Lines: 36


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)