So Now You Know

The speed of 33 1/3 was introduced in 1927 after theoretical analysis of the compromise between signal-to-noise ratio and playing time (3 minutes per radial inch) by J. P. Maxfield of Bell Laboratories for sound films produced on the Vitaphone system. And it was a professional de facto standard before it became commercialized by CBS in 1948. It has been suggested that 78 minus 33 equals 45 was the reason for the emergence of 45 rpm records but, in fact, Maxfield's analysis still applies: the 45 "single" was RCA's equivalent to a 10-inch, 78 rpm record, only smaller.