GB315501A - Improvements in or relating to diaphragms for acoustic instruments - Google Patents

Abstract

315,501. Paul, R. W. Jan. 24, 1929. Diaphragms; loud-speakers. - The diaphragm of a moving-coil loud-speaker or like acoustic instrument is in the form of a flat disc, of light wood such as balsa wood, mounted so as to be free to vibrate as a whole perpendicular to its plane and carrying the coil, being stiffened by ribs formed on or attached to the disc and dividing the surface into asymmetrical areas. Its mass may be further reduced by perforations covered by doped fabric pressed into domed form, and may be supported on threads or flexible washers. The diaphragm A, Figs. 1 and 2, is perforated at A<*> and covered with fabric C, while ribs D and an actuating coil B' are fastened to it. Threads E, E<1>, E<2>, and F, F<1>, F<2>, joined to the diaphragm and coil respectively support them centrally with respect to a magnetic system, as in Fig. 8, in which A<3> is the diaphragm B<6> the moving coil, and E<6> and F<3> are two of the supporting threads. Two of the latter may supply current to the moving coil. For centring the coil and diaphragm the threads E<6>, F<3>, &c. are secured to rotatable pins U, W, &c. held by clamps V on a bracket S. The annulus R surrounding the diaphragm A<3> may be surrounded by a baffle X. In another system of suspension, flexible washers H, H<1>, Fig. 4, shown in detail in Fig. 6, are anchored at the centre to a rod L inserted into the magnet pole M<1> and joined to the rings G and G<1> on the diaphragm A<2>. The washers H and H<1> are pierced by spiral apertures J, and mav be of celluloid, doped paper, &c. An extension L<2> of the rod L carries an insulating block I and fixing set screw O which supports terminal strips P<1> to which are soldered flexible connections Q from the moving coil. A feature of this construction is the facility with which the whole unit comprising diaphragm, coil, leads, and support may be withdrawn from the magnet system.