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From: gjphw@iham1.UUCP
Newsgroups: net.audio
Subject: Re: record speeds
Message-ID: <219@iham1.UUCP>
Date: Mon, 24-Sep-84 12:10:09 EDT
Article-I.D.: iham1.219
Posted: Mon Sep 24 12:10:09 1984
Date-Received: Wed, 26-Sep-84 08:29:15 EDT
References: <591@clyde.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 42



   This is a comment about the origin of the 45 rpm record speed.  All other
 speeds have probably been dictated by some other market or engineering detail.

   The first recordings and use of flat records (rather than drums) came from a
 series of experiments performed by Bell Laboratories in the 1930's.  This was
 the outgrowth of studies devoted to voice storage and reproduction technology.
 As I have read (in AUDIO magazine) but forgotten all of the names, the
 research team consisted of a few engineers and mathematicians.  Several lines
 were run from New York City (Radio City Music Hall??) to Bell Labs in NJ in
 order to have suitable source material for making recording experiments at any
 time.

   The mathematicians on the project were concerned with discovering the
 optimum recording speed that would balance the requirements for good signal-
 to-noise ratio, high fidelity (wide bandwidth that matched the human hearing),
 and reasonable storage (amount of source material).  For 12 inch records, this
 optimum speed is 45 rpm.

   I suspect that most of the other speeds exist due to technological
 limitations at the time.  The faster 78 rpm records were probably used because
 the original mastering and cutting techniques did not yield good results at a
 slower speed.   I don't know why specifically 78 rpms was selected.  Perhaps
 it was related to the availability of electric drive motors which were
 inexpensive at that time.

   All of the speeds slower than 45 rpm are designed to pack more material onto
 the same disk, sacrificing some technical parameters for marketing
 considerations.  I have read that the few 45 rpm, 12 inch audiophile disks
 that are available sound marvelous.  It would be interesting if someone could
 compare and contrast one of these 45 rpm analog pressings against the newer
 CDs.

   Anyone else have specific knowledge about the reasons for 78, 33 1/3, etc?

-- 

                                    Patrick Wyant
                                    AT&T Bell Laboratories (Naperville, IL)
                                    *!iham1!gjphw