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Path: utzoo!utcsrgv!newman
From: newman@utcsrgv.UUCP (Ken Newman)
Newsgroups: net.audio
Subject: Re: Are all DADs alike?(+ phase response of speakers)
Message-ID: <1876@utcsrgv.UUCP>
Date: Tue, 2-Aug-83 20:27:32 EDT
Article-I.D.: utcsrgv.1876
Posted: Tue Aug  2 20:27:32 1983
Date-Received: Tue, 2-Aug-83 21:11:14 EDT
References: <2107@tekmdp.UUCP>, <2435@rochester.UUCP>
Organization: CSRG, University of Toronto
Lines: 26


There is an excellent article in the July 83 High Fidelity, p. 17, called
"CD sound: Trouble in Paradise?", by E. Brad Meyer, president of the 
Boston chapter of the AES. It seems to hit some interesting nails on the
head regarding poor sound quality from some cd disks. He talks mainly
about recording techniques being unsuitable for cds.

The ringing in square waves from cd players is caused I believe by the
very steep filters used to attenuate response above 20 kHz. Remember also
a square wave is a very severe test signal and a good square wave at
frequency f indicates good response out to roughly 10f. Also the square
waves present on most test records probably have some ringing themselves.

While we're talking about phase response in speakers, an interesting technique
is/was used in the Ohm F speaker. These things have a single driver, a
bullhorn-shaped cone essentially that opens downward. The cone is made of
several different precision materials of carefully controlled densities,
and is excited at the top around its perimeter, causing a circular wave
to travel down the cone. Short wavelengths dissipate quickly, and radiate
from the top, long wavelengths travel the whole cone and radiate from the
full length. The result is a completely phase-coherent cylindrical (360 deg)
sound front. What's even more amazing is that this apparently worked (they
were kind of inefficient though).

K. Newman
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