GB215104A - Improved means for reproducing sound - Google Patents

Abstract

215,104. Round, H. J. Feb. 5, 1923. Adjusting relative strength of different ranges of speech frequencies; magnetic instruments.- For transmitting or reproducing sound a number of magnetic, electrostatic, piezo-electric or other telephones with differently tuned diaphragms are connected in series with a variable shunt across each instrument. A suitable form of magnetophone is shown in Fig. 2 in which a central core F carries a magnetizing coil H and a line coil G, the magnetic circuit being completed through the diaphragm E and the case D. Adjustable rubber pads J are arranged adjacent the diaphragm. The diaphragms of different pitches may be constructed of iron of different thicknesses. A very good reproduction of the human voice is stated to be obtained by using two diaphragms tuned to frequencies of 6000 and 600, and for the reproduction of music in which bass is present five diaphragms are used tuned to frequencies of 200,. 500, 900, 2000, and 8000. Where sufficient mechanical damping cannot be obtained, the shunt may consist of inductance, capacity, and resistance. In a modification, the winding of a telephone having a diaphragm pitch about 2000 is connected with a plurality of filter circuits Q in parallel, each adapted to select a different range of frequencies, these ranges being amplified to the desired degree by thermionic valves R, S, and the results synthesized. A plurality of diaphragms differently tuned or a single diaphragm to which is applied a current distorted bv parallel filter circuits may be used in a loud speaker with a single horn of great effective length so that it is practically equally resonant to all frequencies above 100.