GB282931A - Method of and apparatus for radiating sound waves - Google Patents

Abstract

282,931. Jackson, L. Mellersh-, (Acme Apparatus Co.). Oct. 20, 1926. Loud-speakers; magnetic instruments; diaphragms.- In a loud-speaker a variable magnetic flux is superposed on a constant magnetic flux and is converted into two equal and opposite longitudinal motions which are transmitted to flexible supporting members. The flexible supporting members may comprise magnetic discs 28, Fig. 5, or cantilever springs 53, Fig. 10, or thin plate springs bolted at their ends. The weight of the vibrating system may be reduced by substituting a four-armed spider for the disc 28. Two oppositely directed armatures 34 are mounted on the flexible members within a magnetizing coil 42. The constant flux may be provided by a permanent magnet 25 or this may be dispensed with when the operating current is the output circuit of a thermionic valve. In a modification the exciting coil is disposed around one or both of the flexible members. The air gap is preferably 0.005 inches and the arrangement is preferably such that the gap reluctance equals the leakage reluctance. A screw 47 may be used to adjust the gap and a magnetic shunt 48, Fig. 7, be provided to adjust the leakage flux. A pair of diaphragms 37, 38, Fig. 5, or a single diaphragm 37, Fig. 20, may be employed and provision is made as by enclosing in a casing 27 to prevent interference between the two sides of a diaphragm. The diaphragm is preferably conical and waves from either surface may be utilized and the depth of the cone may be varied to secure the desired radiation distribution.