GB244051A - Improvements relating to electro-dynamic loud speakers - Google Patents

Abstract

244,051. Bothe, O. Dec. 4, 1924, [Convention date]. Mouthpieces and earpieces ; diaphragms.-An electromagnetic loud-speaker comprises behind its diaphragm 25, a body 32 of wood &c., the radial cross-section of which is triangular, by means of which body the space behind the diaphragm 25 is divided into two parts 33, 34, the periods of oscillation of which are favourable for eliminating resonance. These spaces communicate only through an aperture in the centre of the body, where the middle of the diaphragm is connected to an aperiodically oscillating flat spring 22. The casing 3 is closed by an apertured cover 5, and contains an electromagnet 8, 9 and a cylindrical iron core 10, both secured by a screw 16. Thin annular surfaces 7 secure the two parts 8, 9 together. In the annulus between the core 10 and the magnet 8 is fitted a coil 19 of fine wire, forming a " sleeve " or cap with an opening through which, and also through the central opening in the cruciform spring 22, passes an ivory &c. fastener 36. A ring 37 completes the fastener, the parts being glued or cemented together under pressure. The cup-like part of the fastener 36 is filled with quicksetting glue or cement, and receives the projecting central part 26 of the conical diaphragm 25, which is further secured at its edges by a ring 30. The diaphragm is of light material, such as celluloid or bakelitized paper, and is deeper than the body 32. The space 40 can be filled by a filling mass or body. Wires 17, 21 excite the coils 14, 19 respectively. The arms of the spring 22 are wider at their outer parts than at their inner. Specification 240,425 is referred to.