GB464386A - Improvements in or relating to microphones - Google Patents

Abstract

464,386. Microphones. ELECTRICAL RESEARCH PRODUCTS, Inc. Oct. 26, 1936, No. 29041. Convention date, July 11. [Class 40 (iv)] A microphone comprises a magnet structure defining a plurality of air gaps located in angular relationship and conductive ribbon diaphragm means disposed in the air gaps and lying in one plane or in substantially the same plane. The diaphragm means may be a single ribbon in the shape of a cross, or two adjacent ribbons crossing each other at right-angles. As shown in Fig. 1 four U-shaped permanent magnets 21 are assembled with two sets of like poles in contact and two pairs of unlike poles separated by blocks 22 of non-magnetic material, e.g. aluminium, secured to an annular supporting plate 23. The magnets carry polepieces 26, 27, 28, 29 forming gaps 31, 32 in which are located ribbons 33, 34 lying in planes spaced at a small distance and supported in blocks 35 of resilient material located in recesses 36 of members 37 secured to the polepieces. In a modification, Fig. 7, the end of each ribbon is supported in a resilient member 39 held in a recess 40 at the apex of an angular or wish-bone spring H secured to a support 42 mounted on the polepiece. The ends of the ribbons 33, 34 are connected in series to a transformer, Fig. 4 (not shown). In a modified arrangement, Figs. 9 to 11 (not shown) and Fig. 13 (not shown), the ribbons form a unitary member in the shape of a cross and, as indicated in Fig. 12, 'the ends of the ribbons 33, 34 are connected to two primary windings 47, 48 of a transformer 46. In a further modification, Fig. 14, the ribbon 55 is circular and the outer polepiece 63 has gaps 62 through which pass corrugated supporting strips 58 having slits 65 covered with silktissue. The ends 56 of the ribbon are brought out to terminals 57, and a space 66 between the conductors is covered with silk tissue. The ribbon diaphragm may be in the form of a hollow square.