GB427590A - Improvements in loud speakers - Google Patents

Abstract

427,590. Loud-speakers. TENNANT, W. J., 111, Hatton Garden, London.-(Rola Co. ; Cleveland, Ohio, U.S.A.) May 2, 1934, No. 13310. [Class 40 (iv)] Relates to a moving coil loudspeaker as claimed in Specification 426,846 in which the air gap is shielded against entry of foreign particles by means of a felt &c. layer 28 clamped between the outer magnet pole 12 and one of the channel-shaped members 21, 22 between which the outer edge of the coil centring member 17 is clamped. According to the invention one of the transverse walls enclosing the substantially cylindrical region adjacent the gap is provided with one or more openings across which extends a fibrous covering which is impervious to the passage of objectionable particles but pervious to the passage of air. Thus the pole 12 may be provided with openings 35 across the front or back of which extends a layer 37 of thin felt or loosely woven fabric. Alternatively, the solid centring member 17 may be replaced by an openwork spider having a layer of thin felt &c. cemented to the arms thereof. The open end of the diaphragm 16 is closed by a cap 30 of the form shown and the leads 50 from the moving coil 14 which extend to the terminal block 51 may be supported at an intermediate point by a rectangular strip of insulating material 60 fastened to a flange of the member 21.