GB782549A - Electrostatic transducer - Google Patents

Abstract

782,549. Electrostatic loud-speakers. JANSZEN; A. A. Sept. 19, 1955 [June 21, 1955], No. 26786/55. Class 40 (4). An electrostatic loud-speaker comprises a diaphragm 20 supported under tension by the margins of a pair of insulating frames 12, 14, and grids of parallel wires 24 on opposite sides of the diaphragm secured at one end only to a bus-bar 28 or 30, respectively, the other ends of the wires being free to move under variations of temperature. The wires are enclosed in sheaths 26 of rubber-like material which are cemented into grooves 22 in vertical webs 18 of the frame, the wires being thus spaced about 0.01 inch from the diaphragm. The horizontal webs 16 of the frame grip the diaphragm 20 and at certain junctions of the webs 16, 18 the frames are held together by pins 52 which pass through the diaphragm. The busbars 28, 30 are at opposite ends of the loudspeaker and are connected to input terminals 34, 36. The diaphragm is a thin sheet of vinylidene chloride coated on both sides with graphite. The tension of the diaphragm is varied while subjected to a predetermined acoustic frequency until it resonates before being clamped between the cemented faces of the frames. A polarizing voltage of about 1000 is applied across the electrodes by the circuit shown in Fig. 8. Mains voltage is transformed at 70, rectified at 72, 74 and applied to the midpoint of the secondary of the coupling transformer 80 and to the diaphragm through resistor 82. If two or more speakers are used additional resistors 84 are inserted. The current used is very small. An amplifier feeds a filter circuit 86, 88, 90 with a lower cut-off of 800-1000 c/s. Values are given for the components. A number of the speakers 62 may be arranged in a corner cabinet 60, Fig. 7, which also includes an amplifier and cross-over network. The prior state of the art is represented by a reference to U.S.A. Specification 2,631,196.