GB372417A - Improvements in moving-coil loud speakers - Google Patents

Abstract

372,417. Loud-speakers. GUTHRIE, J. A., Oakland, Tumble, near Llanelly, Carmarthenshire. Feb. 13, 1931, No. 4522. [Class 40 (iv).] A moving coil loud-speaker has the moving coil situated in a single air gap between a pair of inside poles of like polarity and in magnetic continuity and an outer concentric pole of the reverse polarity. Fig. 1 shows a construction in which the moving coil e is located in the gap m between a pair of cores b, b and an outer concentric pole a, the magnetic circuit being completed by the outside core c and endplates d. The cores b may be spigoted at g and separated over the remainder of their faces by non-magnetic material l. The cores are also formed with radial slots to accommodate plain, ribbed or corrugated members f which connect the coil e to a transmission tube h passing through one or both cores to a diaphragm or diaphragms and supported by members i. When an electromagnet is used, the spaces k are filled by the energizing coils. According to a modification, Fig. 3 (not shown), the cores b are formed in one piece and movement of the coil e is transmitted to the diaphragm by tubes arranged along the outside of the core b and through the endplate d. Fig. 5 shows a further modification in which the diaphragm is arranged within the magnet structure, movement of the coil e being transmitted by the radial members f to the periphery of the cone. Supports i are provided as shown at the apex and periphery of the cone.