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English: Westinghouse Vocarola loudspeaker, an early radio loudspeaker sold between January 1922 and September 1923. Like most early speakers it was a horn loudspeaker, which used a coiled brass horn to amplify the sound produced by a small metal diaphragm vibrated by an electromagnet in the small cylindrical box (right, near bottom). It could either stand on a table or be attached to a wall. The cord plugged into the earphone jack of a radio. Two models were made: the Type I shown here, and the Type LV. It initially sold for $30, reduced to $18 the next year.

The speaker was designed by Frank Conrad from an automobile horn. When radio broadcasting suddenly began in 1920, creating a demand for family listening, there were not many speakers on the market; most radios used earphones. Conrad tried attaching a reproducer from a Baldwin telephone earpiece to the coiled brass sound duct from an automobile horn. It worked well enough that he kept this design. The original mica diaphragm of the earpiece was replaced with a metal diaphragm to handle the higher power. (Information from Eric Wenaas (2007) Radiola: The Golden Age of RCA 1919-1929, Sonoran Publishing, p.142-143 )