GB694058A - Improvements in and relating to loud speakers - Google Patents

Abstract

694,058. Loudspeakers. MILNES, H. R. Dec. 14, 1950, No. 30566/50. Class 40 (iv). In a loudspeaker in which the central pole 5 is a multi-faced prism, a single layer coil 3 is supported by the cranked ends of arms radiating from a central base which arms work in recesses in the centre pole and form a resilient connection to the diaphragm 24. The central hexagonal pole 5, Fig. 1, and the outer polepiece 7 define a gap in which the coil 3, which may be a single turn of conducting material or a single-layer coil, is free to operate. The coil is supported on the bent up ends 11 of radial arms 10 and tension is maintained by the ends 17 of the intermediate arms 16. The turned up ends 11 and 17 are accommodated in recesses in the inner and outer pole faces respectively and serve to centre and guide the coil. For ease of construction the coil is wound on the arms of a spider, Fig. 11, and the whole is fitted within the turned up tensioning arms of a second spider, Fig. 12, to form, when secured by a bolt or a nylon thread, a single unit to which the cone diaphragm may be affixed. The spider and coil are additionally centred by nylon cords 28 the tension of which may be adjusted by a screw 30 and spurious vibration (" ringing ") of the spider parts is prevented by binding them with fine nylon cord or by coating with particles of asbestos. Singly cast spiders are described with reference to Figs. 1-4 (not shown), and in one of these arrangements both the coil supports and the tensioning arms are let into recesses in the inner pole.