English: Magnavox M1 loudspeaker, an early radio loudspeaker, from an advertisement in a 1922 magazine. The horn mouth is 14 inches in diameter. It sold for $35. It consists of a driver unit (bottom) containing a small metal diaphragm vibrated by a coil of wire in a magnetic field, creating sound waves, which were conducted to the outside air through the flaring horn. The purpose of the horn was to couple the diaphragm to the air more efficiently. So horn loudspeakers produced far more sound power than cone loudspeakers from a given audio signal. The weak vacuum tube amplifiers in early radios couldn't produce much output power, and virtually all early loudspeakers used horns to achieve adequate volume.

Edwin Jensen and Peter Pridham invented the moving coil mechanism that made practical loudspeakers possible, and their firm Magnavox produced the first commercial loudspeakers, beginning in 1915. Before 1920 radios were listened to with earphones and didn't come with speakers. When radio broadcasting began suddenly around 1920 it created a demand for family listening, so separate speakers like this one were sold which plugged into the earphone jack. Alterations to image: cropped out loudspeaker image from background drawing.