GB754901A - Improvements in or relating to loudspeakers - Google Patents

Abstract

754,901. Loud-speakers. ELECTRO-VOICE, Inc. Aug. 30, 1954, No. 25154/54. Class 40 (4). [Also in Group XXXVIII] In a moving-coil horn loudspeaker the single driver unit 21 drives a single diaphragm which is coupled at one side to a highfrequency horn 22, and an axial passage through the unit 21 couples the other side of the diaphragm to a re-entrant folded low-frequency horn 23, the highfrequency horn 22 being located within the outer limits of the lowfrequency horn 23 and having its longitudinal axis in alignment with that of the low-frequency horn 23. Construction of horn. The horn 23 consists of an outer bell member 24 within which the folded re-entrant horn portions formed by the exponential members 25, 26 and 27 are supported. At an intermediate point in the bell member 24 a vertical member 32 (Fig. 2) and a horizontal member 33 (Fig. 1) carry at their intersection a supporting structure including a threaded boss 34 (Fig. 2) into which the end of the drive unit 21 is screwed. The end portion 35 of the boss 34 engages the smaller end of member 27, the annular member 36 carried by vertical and horizontal members 32 and 33 engages the smaller end of member 25, and the two inwardly projecting fins 37 within the smaller end of member 25 engage notches in the larger end of member 26. At the rear of the bell member 24 the smaller end of member 26 is supported by the recess 41 in support structure 38, the larger end of member 27 by the two fins 42 inside member 26, and the larger end of member 25 by the two radial extensions 43 of structure 38. The housing 28 screwed to the rear of member 24 serves to house a suitable transformer or matching network. Construction of driver unit, Fig. 3. The driver unit casing 47 screws into the boss 34, the axial passage being provided by openings 49 and 51 in the bottom and top of the casing and by a central passage in the permanent magnet 53. A screen 56 prevents foreign matter from passing through the opening 51, and the inner side of the annular air gap is protected by an annular structure 57 engaging the pole pieces 54 and 55. The diaphragm support ring 63 has washers 61 and 64 on either side of it and is retained by the bolts 65 which secure the cover 48 of the casing 47. The diaphragm proper consists of a cylindrical portion 66 having apertures 67 therein and carrying the moving coil 68, and a domed concavo-convex portion 69. Adjacent the convex side of the diaphragm is a frusto-conical member 71 (held in position by three legs 72) having a frusto-conical throat 73 the outer edge of which is covered by a screen 74. The diaphragm is coupled to the horn 22 via the throat 73 and the annular passageway 70. The holes 75 in the cover 48 serve for the removal of condensate. The diaphragm is preferably moulded of phenolic resin and glass cloth. The Specification describes how a plurality of the loud-speakers may be assembled to form multiple units.