GB345342A - Improvements in or relating to sound-reproducing instruments - Google Patents

Abstract

345,342. Reproducing music. VOGT, H., 17, Genthinerstrasse, Berlin. Dec. 21, 1929, No. 39183. Convention date, July 4. [Class 40 (iv).] In an arrangement comprising a number of separate electrostatic reproducers or a number of electrostatic elements combined in a single reproducer, the reproducers or elements are adapted for reproducing different sub-bands in the voice range by using different spacings between their fixed and vibrating surfaces. In the arrangement shown in Fig. 1, separate reproducers 11, 12, 13 are used for the high, medium and low sub-bands respectively, and the reproducers are of the type comprising a vibrating plate 14 interposed between two fixed plates 16, arrangements for supplying priming voltages being omitted. The single reproducers 11, 12, 13 may be replaced by groups of reproducers. The reproducers are fed by separate amplifying valves connected in parallel, the impedance of the valves being chosen to match the reproducers or transformers 21, 22, 23 of suitable ratio being used. A high impedance valve is used for the reproduction of the low sub-band and vice versa. Each reproducer may be fed by valves arranged in push-pull. The fixed plates of the various reproducers are perforated to an extent dependent on the required frequency response. In the arrangement shown in Fig. 2, the reproducer has a single vibrating plate having a central zone controlled by fixed plates 41 for producing the lower frequencies and an outer zone controlled by plates 42 for producing the higher frequencies. The transformer windings 43, 47 and 44, 46 are mounted on a common core in such a manner that mutual inductance between the two transformers is minimized.