ELECTROSTATIC SPEAKER.

New Zealand Herald, Volume LXVI, Issue 20244, 2 May 1929, Page 20

ELECTROSTATIC SPEAKER.

:high efficiency claimed. Much is expected from a loud-speaker of what is called the electrostatic or condenser tvpc invented by a young Lalifornian, Mr. Colin Kyle. The principle employed is not new, but. American authorities say that Mr. Kyle's improvements have made this form of speaker a commercial proposition. It is claimed to gn e uniform reproduction of the whole range •of musical frequencies with the consumption of very little current. Unlike the dynamic speaker it requires no peiver other "than that supplied by the receiving set. though an additional rectifying valve is needed. . . . The principal upon which the device works is that bodies carrying similar electric charges, either positive or negafcive. repel each other, as in the wellknown experiment with pith balls or strips of gold-leaf. Conversely, bodies oppositely charged attract each other. Mr. Kyle's improvements been directed to making the speaker electroacousticallv efficient, it consists of two metallic plates separated by a special nonconducting material called kylite. By means of a polariser consisting of a transformer, blocking condenser, and rectifying valve, the plates are given charges -which are alternately similar and opposite. They therefore alternately repel and attract each other uniformly over iheir entire surfaces, and mav be io vibrate in phase with the output voltages of the receiving set. As this output is delivered direct to the diaphragms without passing through coils placed in magnetic fields, the speaker is, it is claimed, remarkably sensitive. The same principle has already been applied the other way about in the con-denser-type microphone. Here two closelyset plates vary a charge placed upon them when waves of sound cause one of them to vibrate. As the complete diaphragm of the new speaker is only about a foot squaic -and nn eighth of an inch in thickness, it •can be readily incorporated in a wireless cabinet. Whether the device will be able to compete on equal term 3 -with the moving- ' Coil speaker has yet to be seen.