GB265123A - Electromagnetic sound reproducing systems - Google Patents

Abstract

265,123. Brandes Laboratories, Inc., (Assignees of Rowe, C. R.). Jan. 28, 1926, [Convention date]. Loud - speakers.- In order that the resonance of a loudspeaker may be distributed uniformly through the audiofrequency range, the last stage of a thermionic amplifier system comprises two or more valves whose output is supplied to separate telephone windings, each resonant to a different region of the range. The output of the last amplifier is applied to the valves 8, 9, the outputs of which are applied to separate pairs of windings 11, 11<a>, and 12, 12<a>. The two pairs of windings, which respond to different frequency ranges, may be mounted on opposite sides of a vibratory member 14 which is connected by a pin with a loud-speaker diaphragm, and are so wound that they aid one another's effects, while the steady component of the current in them polarizes the member 14. In a modification, the windings 11, 12 may be on one pole-piece of a telephone magnet and the windings 11<a>, 12a on another, both pole-pieces being on one side of the member 14. In a further modification, three valves like 8, 9 control three different loud-speaking instruments, each system being resonant to a. different frequency range.