GB307450A - Improvements in or relating to conical diaphragms for sound-reproducing and like devices - Google Patents

Abstract

307,450. Clifton, W. E. Dec. 8, 1927. Diaphragms : loud-speakers ; magnetic instruments.-A diaphragm of thin sheet-like material for sound reproducing and like devices, more particularly loud-speakers, is so formed that its surface conforms to that of a cone with the larger end polygonal, e.g. square, in plan. In the constructions shown, the diaphragm is formed from a flat blank 10 of cardboard, manilla board, stout paper &c. of the form shown in either Fig. 1 or Fig. 4, the margins 12, 13 on opposite sides of the gap 11 being overlapped and secured together by adhesive. Fig. 7 shows a construction of loud-speaker in which the diaphragm 10 is mounted on the diaphragm 114 of a unit 14 in the manner described in Specification 304,805. The unit 14 is mounted on a rail 15 extending across the back of a square casing 16, the open front of which is provided with an inwardly projecting flange 17. The diaphragm is mounted in the casing so that its centers are pressed against the flange 17 to which they are preferably secured by pins, adhesive &c. Pads 18 of felt &c. may be inserted as shown, if desired. Alternatively, lugs secured to the diaphragm may serve as the means for securing it in position. The sides of the casing 16 are brought so close to the edges of the diaphragm that they, in conjunction with the flange 17, serve to baffle the diaphragm. In a modification, Fig. 10, the diaphragm 10 is actuated by a coil 21 carried on the outer or inner surface of a former or spider 20 and located in the air gap of a magnet system 22. The inner end of the former fits snugly in the aperture in the smaller end of the diaphragm and abuts against a conical element 23, the diaphragm, former and elements 23 being secured together by adhesive. In -both constructions, Figs. 7 and 10, the flange 17 is preferably secured to the casing 16 by screws passing into the walls of the casing through elongated slots in the flange so that the latter can be adjusted relatively to the casing in a plane adjacent to and parallel with that of the open end of the casing. In the case of the moving coil instrument, this adjustment allows the coil to be adjusted to its optimum position in the magnetic air-gap.