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Old 14th Sep 2019, 1:41 am   #20
Synchrodyne
Nonode
 
Join Date: Jan 2009
Location: Mt. Maunganui, New Zealand
Posts: 2,567
Default Re: Question on Recording speeds

Quote:
Originally Posted by barrymagrec View Post
I was told that the 78 standard was chosen as a compromise because early recordings could be at various speeds between 75 and 80.

No idea if this is true but it would have been difficult for early disc cutters to give a guaranteed accurate speed.
That seems quite plausible.

78.26 rev/min was derived as 1800 divided by 23. 1800 rev/min was the rotational speed of a 4-pole synchronous motor operating from a 60 Hz supply, and was the typical drive motor for industrial/professional equipment, which often used geartrains to effect speed reduction. The latter made integral division down from 1800 rev/min desirable. 1800/22 gave 81.82 rev/min, and 1800/24 gave 75 rev/min. Notwithstanding that 75 rev/min was a “round number”, it was at the lower end of the range of existing recordings, whereas 78.26 rev/min was closer to the middle. So presumably that is why it was chosen.

33⅓ rev/min was 1800/54, original developed for movie sound purposes and then used for transcription recordings and later the LP. 45 rev/min was 1800/40. Even in 1949, some transcription turntables, such as the RCA 70-series, were gear-driven. As described in the earlier thread https://www.vintage-radio.net/forum/...d.php?t=151267, RCA developed a retrofit epicyclic ball-type reduction unit to allow its existing two-speed transcription turntables (33⅓ and 78 rev/min) to also work at 45 rev/min.

That RCA was working on microgroove and vinylite records before WWII, and that Columbia’s work was facilitated by Rene Snepvangers’ move from RCA to Columbia does I think weaken the argument that RCA’s work on the 45 was in total simply an emergency reaction to Columbia’s release of the LP. The 7-inch 45 was in fact a logical choice for popular music, as was a companion fast changer system. If that concept was in existence before Columbia moved, then also using the 45/changer combination for classical music (and other longer works) was a reasonable immediate and short-term defensive move. It is conceivable at least that Columbia chose to develop the LP in part because it saw a need that the microgroove/vinylite combination would address, and in part because it saw that as avoiding a head-to-head clash with RCA, some of whose thinking would inevitably have come with Snepvangers, deduced and inferred by colleagues if not directly stated. Columbia’s immediate defensive response to the RCA 45 was its 7-inch “LP”. But the LP and the 45 were mostly complementary, and that is how both the industry and market saw it. Be that as it may, urban legends and “format wars” are probably seen as being more fun than the often prosaic facts, at least in the world outside of this and similar forums (where drilling down for evidence, often arcane, is much more the norm).


Cheers,
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