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Path: utzoo!linus!philabs!cmcl2!floyd!vax135!cornell!uw-beaver!tektronix!kimr
From: kimr@tektronix.UUCP
Newsgroups: net.audio
Subject: How my ears are built
Message-ID: <1211@tektronix.UUCP>
Date: Thu, 7-Jul-83 00:13:56 EDT
Article-I.D.: tektroni.1211
Posted: Thu Jul  7 00:13:56 1983
Date-Received: Fri, 1-Jul-83 22:30:27 EDT
Organization: Tektronix, Beaverton OR
Lines: 34

The ear, unlike some quasi-techno-freak audio equipment, was not designed to
receive (produce) only sine waves.  Current information is that the ear is 
sensitive to signal RISE times on the order of 10 microseconds.  Instead of
worrying about sine wave response of the ear, think about a 1000 hertz square 
wave with a 10 us rise time.  It has sine wave harmonics exceeding 20 khz, and 
I'll bet that a well designed experiment will show audible differences if the
rise time is limited to (say) 20 us.

Interestingly enough, the chief difference between moving magnet and moving coil
cartridges is their rise times - on the order of 10us for moving coil and 20us
for moving magnet (16us for the Shure V15-V).  A Time-Life book on music, circa
1965, shows the waveform of a kettle drum attack.  The caption indicates that
the rise time of the waveform is 12us.

For reproduction, I use KEF T-27 tweeters that are rated -3db at 37Khz.
The Pyramid T-1 ribbon tweeter is -3db at better than 80 Khz.  Better yet,
the Pyramid Met-7 ($295/pair) has a PUBLISHED rise time of 10us.  I could
continue: Quad ESL -3db @ 35 Khz...

A competent stereo, (with competent source material) can produce an acoustic 
illusion which is 3-dimensional - realistic depth front-to-back, extending
beyond the speakers to the sides, and most interestingly, top to bottom
placement of instruments.  You should be able to tell where the performers
are in relation to the walls of the space they're performing in.  And, if
all goes right, you can convince yourself that you're attending a live 
performance, not listening to a mechanical reproduction.

Until your system can reproduce this kind of illusion, it is far from the
state of the art.  And until the illusion is perfect, there is room for
inprovement in the technology.  AND UNTIL THAT'S TRUE, QUIT TELLING ME THAT
IT'S BETTER THAN I CAN HEAR, BECAUSE IT'S NOT!!

                                 Kim Rochat
                                 ..!tektronix!kimr