[NJARC] Record speeds

[amagoun]

Nick,

78.26... was the speed for records played on a worm-drive electric motor, standardized in the 1920s.  Until then, what we call 78s
varied in correct speed from the 60s to the 80s in rpm.

33 1/3 was the initial speed AT&T used for its talking picture records, based on record dimensions and groove pitch to match a
15-minute reel of 35mm film.

45 was at the low end of about 9 rpm that RCA Victor engineers determined would fit both fast and practical record changing and
the least noticeable forms of harmonic distortion to the record.  They were also aware of the convenient additive coincidence with
33 and 78.

16 2/3 was apparently Peter Goldmark's choice for the 7-inch CBS longplaying record initially designed to double the playing time
of an LP in a glove-compartment-sized turntable for automobiles.  Others later adopted the speed for spoken-word recordings that
require less frequency range than much music.

Alex

njarc-request at mailman.qth.net wrote:

Message: 4

> Date: Sat, 3 Mar 2007 20:47:55 -0500 (GMT-05:00)
> From: Nick Senker <ns539 at earthlink.net>
> Subject: [NJARC] Record speeds
> To: NJARC <njarc at mailman.qth.net>
> Message-ID:
>         <11445780.1172972875999.JavaMail.root at elwamui-hybrid.atl.sa.earthlink.net>
>
> Content-Type: text/plain; charset=UTF-8
>
> Does anyone know where the standard recording speeds came from (16/33/45/78 rpm)?  They seem to be odd intervals.  Nick Senker

--
Alexander B. Magoun, Ph.D.
Executive Director
David Sarnoff Library
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