Re: 78 rpm
- From: "Kevin P. Mostyn" <notmyrealaddress@xxxxxxxxxxx>
- Date: Tue, 13 Nov 2007 07:16:41 GMT
33 1/3 was determined by several things; the amount of time that could be
recorded on a 16" disc, the ability to synchronize with the gears in a
motion picture projector running at 24 fps, the ability to make a strobe
disc that could be read under 50 or 60 Hz lamps, etc.
78.26 was also determined by strobe requirements.
Some years ago, I had an exchange with Dr. Michael Biel, a maven of all such
things. Here is the exchange, from a public mail list. Please note that he
is quite gentle in correcting my unaided and partially faulty memory of an
article that I had read some decades earlier.
--
Kevin Mostyn
---------------------
my real e-mail address is my first name at my last name dot com
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Date: Tue, 08 Sep 1998 22:18:10 -0400
From: "Michael Biel mbiel@xxxxxxx" <mbiel@xxxxxxx>
To: 78-l@xxxxxxxxxx
Subject: Re: [78-l] Speed, was Re: History of Transcriptions?? why 9
minutes?
koussy@xxxxxxx wrote:
A few decades ago I read an extensive interview with a retired British
scientist who had been on the team at Western Electric that developed the
"Vitaphone" system of sound recording. It was published either in "Hi-Fi
News" or its predecessor "Tape Recorder."
The wonderful article you are referring to is "Babyhood of the Talkies"
by Stanley Watkins in __Hi Fi News & Record Review__ December 1966, pp.
695-699.
One of the questions put to him concerned the origin of 33 1/3 rpm as a
recording speed. While all the reasons posted here by M. Biel and others
are correct, the interviewee stated that the precise reason for choosing
33
1/3 was that it was in the necessary range of speeds for the required
length of recording and quality of recording, and that it was the *ONLY*
speed in that range that would mechanically synchronize the turntable and
the film camera. It had to do with the ratio of the gears.
I am sorry that I cannot give an exact reference, as I no longer have the
magazine, and I hope that my recollection is accurate.
Kevin P. Mostyn <koussy@xxxxxxxxxxxx>
Since I do have the article, let me mention that he did not quite state
that 33 1/3 was the ONLY speed they could use. He really seems to say
that it was the most convenient. "To get ten minutes of recording of a
disc of that size (there was no microgroove technique then) the best
speed was about 35 R.P.M. We chose 33 1/3 because it fitted in with the
gearing that the engineers in the labs were designing to couple the
record turntable to the projection machine."
The recording turntables were synchronized with the cameras by
synchronized motors, so this was not as critical to the decision. The
projector playback turntables were directly connected to the projector
and run by the same motor. This gearing was probably more critical than
the recording table, but other speeds could probably have been
accommodated.
33.33 was a nicer number than most of the others they could have used.
Having speeds that could be checked by strobe disc in both the 60 and 50
cycle electrical current areas was very important--and most likely these
speeds would also fit into the gearings they were preparing. The other
speeds in this range that show up in both frequency lists are: 30.00,
30.77, 31.58, 32.43, and 37.50. It really is too bad they didn't pick
30.00, but they probably didn't want to stray too far from that 35
figure.
In past months we have discussed the selection of 78.26 and stressed
that it was a strobe-disc related speed rather than a geared turntable
question. I want to remind everyone that all domestic turntables used
either variable-speed governors or non-gear drives or both. Only these
film turntables and some of the broadcast turntables that evolved from
them used gear drives. So while the gear story that has been related in
conjunction with the selection of 78.26 is quite false, projector
turntable gearing is part of the story of 33 1/3--but so is the strobe
disc.
Mike Biel mbiel@xxxxxxx
--End of message--
-----------------------------------------------------------------------
"Matthew B. Tepper" <oyþ@earthlink.net> wrote in message
news:Xns99E6DD45A6B4quackandflap@xxxxxxxxxxxxxxx
lawnch@xxxxxxxxx (Lawrence Chalmers) appears to have caused the following
letters to be typed in
news:7880-47392811-140@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
How was this 'rpm' determined for commercial recordings on disc?
I think the various well-known disc speeds (78, 45, 33 1/3) were
determined
by the speeds on easily-available motors, and the speeds that resulted
from
using easily-available gears in the works.
--
Matthew B. Tepper:
.
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