GB326296A - Improvements relating to sound reproducers - Google Patents

Abstract

326,296. Mullard Radio Valve Co., Ltd., and Hodgson, B. Jan. 28, 1929. Magnetic instruments; diaphragms. -A sound-reproducer adapted to be operated by radiofrequency currents has a large diaphragm of substantially conical shape and a coil, fixed or movable, for receiving modulated radio-frequency current and a second con or conductor, inductively or conductively coupled with the first coil, so that attractive or repulsive forces are set up between the two. The diaphragm may be attached to either coil or conductor. The diaphragm 1, Fig. 1, mounted as in Specification 308,448, is attached to a coil 5, co-operating with a fixed coil 6, the flexible leads 7 to the coils being taken from terminals 8, 9. The coils may be connected in series or one coil may be short circuited to give either an attractive or repulsive force between the coils, and the fixed coil may have an iron core. The springs 10 supply the restoring force. In a modification, Fig. 3, the coil 5 is replaced by a conical metal cap 11 and the coil 6 is of conical form and is supplied with the currents. The diaphragm may also be actuated at its periphery. The speaker may also operate with audio frequency currents, the output from an audio frequency amplifier being connected so as to cause modulation of high frequency oscillations. The circuit of the input coil may be tuned to the frequency of the radio frequency current by connecting a variable condenser across the coil, and the radio frequency supplied may be derived from the intermediate frequency amplifier of a supersonic heterodyne receiver. The diaphragm may be supported by an elastic medium at its edge.