GB1318823A - Electrostatic loudspeakers - Google Patents

Abstract

1318823 Electrostatic loudspeakers AUDIO SERVICES Ltd 23 April 1971 11053/71 Heading H4J In an electrostatic loud-speaker comprising two apertured plate electrodes 11, 12 (Fig. 2) and a flexible diaphragm 10 having an electrically conductive face 13, a film 16 of electrically insulating material is disposed between the electrically conductive face 13 and the electrode 11. The film 16 has apertures 17 coincident with the electrode apertures 15 and the marginal areas of the apertures 17 extend partially across the apertures 15 of the electrode 11. Thus, the shortest air path between the electrode 11 and the face of the film 16 remote from electrode 11 is greater than the thickness of the film 16. Preferably, the film 16 is secured to the electrode 11. Monofilament thread 14 secures the diaphragm at intervals along its length. The diaphragm 10 may be conductive at both faces (Fig. 3, not shown), an insulating film 16 then being secured to each electrode 11, 12. A local circuit (Fig. 1, not shown) has a pushpull electrostatic loud-speaker with its electrodes 11, 12 connected to the secondary winding (5) of a transformer (4). The diaphragm 10 is connected through a D.C. polarizing voltage source and a resistor of 10 to 20 megohms to a centre tap (6).