GB1350122A - Sound reproducing equipment - Google Patents

Abstract

1350122 Loud-speakers; diaphragms ELECTRONIC RESEARCH ASSOCIATES Inc 19 April 1971 9775/71 Heading H4J A loud-speaker assembly Fig. 1, comprises a substantially flat diaphragm 18, see Fig. 3, yieldably secured at spaced points around its periphery to ledge portions 12 of a frame 2 by flexible adhesive. Air spaces between the diaphragm 18 and ledge portions 12 present air release passages 94 (Fig. 7) (96, 98, 100, Fig. 2, not shown) to minimize the damping action of air adjacent the diaphragm periphery. A voice coil form 24, e.g. of plastics coated paper or aluminium, is secured near the centre of the diaphragm 18. The voice coil 32 is in an air gap defined by a magnet assembly 30 mounted on a support 28 which extends generally parallel to the diaphragm 18 and is secured to sides 4 and 8 of the frame 2. The magnet assembly 30 comprises a permanent magnet 34 together with inner and outer plates 40 and 36 and a central pole piece 38. The frame 2 has horn-like inclined surfaces 22 at the periphery of the diaphragm 18. The assembly may be rectangular, as shown, or circular or elliptical. The frame 2, diaphragm 18 and support 28 are preferably either formed of the same material such as a solidified foam or expanded beads of polystyrene or of materials having matching acoustic and physical characteristics. Alternatively the frame 2 and support 28 are integrally moulded of unexpanded plastics material, whereas the diaphragm 18 is of expanded polystyrene. The magnet assembly 30 is moulded in place with the support 28. The diaphragm 18 has compliance rings, lines or corrugations such as rings 50, 52 on the front and rings 54, 56, 58 and 60 at the rear. Silicone rubber material is inserted into at least the rings 50, 52. The diaphragm periphery is secured to ledge portions 12 by yieldable cement 48 such as silicone rubber. Parts of the ledge portions 12 are cut away or moulded to leave the air release passages 94. "Dabs" 102 of relatively rigid bonding material are provided. An element 72, Fig. 8, provided with a central depression 76 is surrounded by a vibratory element 78. Element 78 is a thin metal ring, is cemented to element 72 and extends over and beyond a horn-like surface 66 of the diaphragm 18. It is actuated directly by the voice coil 32.