GB448271A - Improvements in and relating to sound reproducing devices - Google Patents

Abstract

448,271. Loud-speakers; microphones. BARKER, A. C., The Close, Hurstpierpoint, Sussex. Dec. 5, 1934, Nos. 34967/34 and 19824/35. [Class 40 (iv)] An actuating element for an electrodynamic reproducer comprises two moving conductors which are mechanically coupled by a resilient connection and are inductively coupled so that one conductor has currents generated in it from the other. One of the conductors may be directly connected to a diaphragm and the second conductor is indirectly attached to the diaphragm through its resilient connection with the first conductor. As shown in Fig. 1, a thin metal member 12 is secured to the diaphragm 13 centred by the usual spider 15 and is resiliently connected by rubber rings 14 to a paper ring 11 secured to a moving coil 10. In a modification, Fig. 2 (not shown), the paper ring 11 is extended longitudinally and secured to a ring of felt located between the spider 15 and the thin metal ring 12. In a further construction, Fig. 3 (not shown), the paper ring carrying the coil is secured to the spider at a position spaced from the junction of the metal ring and the cone diaphragm. The resilient connection between the member carrying the coil and the metal ring may be provided by the diaphragm itself or by the spider. In a further modification, Fig. 6 (not shown), generally similar to Fig. 1, the metal conductor 12 is centrally disposed between two coils and the associated sets of rubber rings. Fig. 7 shows a construction in which the resilient connection between the coil 10 and the thin metallic ring 12 connected to the diaphragm is effected by forming two ridges or crimps 20 in the paper support 11 of the coil 10. The constructions described may be used as microphones by constructing the conductor 12 as a cup of which the end portion 12a forms the diaphragm of the instrument. The member 12 may have holes 19 in the portion not in the air gap of the magnet system to increase the response of the instrument. The cylindrical metal conductor ring may be formed by stamping aluminium foil into a cup of which the end is removed. Alternatively, the member 12 may be formed by coating paper with aluminium by a spraying or electroplating process.