Audio disc playing speed

The early Berliner discs played at 70 rpm. From 1900 to 1925 playing speed hovered between 74 and 82 rpm, then became stabilised at 78 rpm with the introduction of electrically powered turntables.

The 33.33 rpm speed was used prior to LPs by the broadcast industry on sixteen inch coarse groove transcription discs. The advent of microgroove allowed the same playing time on ten or twelve inch discs.