UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Why were the RPM speeds of records chosen

David G4EBT · 26th Nov 2014, 11:10 am

Peter Copeland, of the British Library National Sound Archive, London, gives a comprehensive explanation at ‘Vinylville’ at the link below.

Briefly, he states that records of 33 1/3 rpm were developed in conjunction with films. A 12-inch 78 with Berliner-type grooves could hold between 4 and 5 minutes per side. The first practical sound films produced in the US in the late 1920s had their sound on separate disc records and it was more important for the sound to be continuous. A reel of film might run for 11 minutes, so a rotational speed of about 32 rpm was required to make the sound match the picture.

Much more information here:

http://vinylville.tripod.com/spindoc.html

Here’s a clip from the link below which sounds plausible:

Clip 8-<

"The exact value of 78.26 rpm was not standardized till the 1920s. I believe that it was set according to the electric motor commonly available, which gave a speed of 3600 rpm, and a commonly available gear (46:1), so that it would fall in this range. As can be seen, 3600/46 = 78.26. The site further explains about 45 & 33 RPM. Not the done thing to copy chunks of text from internet sources, but suffice to say that this site also confirms Peter Copeland’s explanation that the development of ‘talkies’ necessitated longer playing time than a 78RPM record was capable of. 78 rpm offered very high quality, but the disc could hold only 4-5 minutes of music. On the other hand, a film reel lasted 11 minutes".

End clip 8-<

More information about motor speeds and ratios etc, and lots of other questions and answers that might spring to mind:

http://www.quora.com/How-were-the-ro...-78-rpm-chosen

Wiki also has lots of stuff:

http://en.wikipedia.org/wiki/Gramophone_record

Hope that's of interest.

26th Nov 2014, 11:10 am	#5
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,766	Re: Why were the rpm speeds of records chosen Peter Copeland, of the British Library National Sound Archive, London, gives a comprehensive explanation at ‘Vinylville’ at the link below. Briefly, he states that records of 33 1/3 rpm were developed in conjunction with films. A 12-inch 78 with Berliner-type grooves could hold between 4 and 5 minutes per side. The first practical sound films produced in the US in the late 1920s had their sound on separate disc records and it was more important for the sound to be continuous. A reel of film might run for 11 minutes, so a rotational speed of about 32 rpm was required to make the sound match the picture. Much more information here: http://vinylville.tripod.com/spindoc.html Here’s a clip from the link below which sounds plausible: Clip 8-< "The exact value of 78.26 rpm was not standardized till the 1920s. I believe that it was set according to the electric motor commonly available, which gave a speed of 3600 rpm, and a commonly available gear (46:1), so that it would fall in this range. As can be seen, 3600/46 = 78.26. The site further explains about 45 & 33 RPM. Not the done thing to copy chunks of text from internet sources, but suffice to say that this site also confirms Peter Copeland’s explanation that the development of ‘talkies’ necessitated longer playing time than a 78RPM record was capable of. 78 rpm offered very high quality, but the disc could hold only 4-5 minutes of music. On the other hand, a film reel lasted 11 minutes". End clip 8-< More information about motor speeds and ratios etc, and lots of other questions and answers that might spring to mind: http://www.quora.com/How-were-the-ro...-78-rpm-chosen Wiki also has lots of stuff: http://en.wikipedia.org/wiki/Gramophone_record Hope that's of interest. __________________ David. BVWS Member. G-QRP Club member 1339.