>Just back from the pub after one of THOSE conversations. Can anyone
>help with this one?
>Why was the first record speed 78rpm?
It wasn't, exactly. Early discs (Berliners) turned at anywhere from
70 to 80 rpm, and larger discs (14") turned at 60 prm. Overseas,
the larger French Pathe discs turned at over 100 rpm. Even domestic
recordings often varied throughout the early years (1900-1915), and
anything between about 75rpm and 82rpm was considered fairly
"normal". It wasn't until the 1920s, that the recording speed was fixed
at 78rpm (actually it was a fraction over that.)
>Why did this then become 33rpm for LPs and 45rpm for singles?
It wasn't planned that way. Victor had unsuccessfully tried a
33rpm disc in 1931, but mediocre quality and the depression prevented
commercial success. Peter Goldmark (of Columbia) achieved a
microgroove 33.3rpm record in 1947 which was introduced to the
public in June, 1948 in New York.
RCA Victor countered early the following year with the 45rpm record. Both
were intended to replace the conventional "78". RCA brought out
symphonies on 45rpm, and sold "albums" in boxed sets.
But the problem was that the playing time of the "45"
was still only in the 4-5 minute range, and breaks were still necessary,
even within movements of a symphony.
For extended selections, the public preferred the uninterrupted 33rpm,
but the 45rpm was perfect for singles. Due to generous cross-licensing
agreements, both Victor and Columbia (as well as numerous other smaller
companies) were each producing both speeds by the early 1950s.
>Is there any significance in the relationship: 33 + 45 = 78?
Not to my knowledge.
Hope this helps.