GB382514A - Improvements in or relating to magnet systems for electroacoustic devices, such as loudspeakers or the like, comprising a permanent magnet - Google Patents

Abstract

382,514. Magnets. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. March 1, 1932, No. 6215. Convention date, June 10, 1931. [Class 35.] In a loud-speaker &c. magnet system, preferably of the balanced armature type, comprising at least one permanent magnet and having one or more air gaps in which there is a magnetic field of given intensity, the volume of the magnet is smaller than four times the volume of the air gap or gaps belonging to that magnet multiplied by the square of the intensity of the field and divided by (BH)max of the steel used, all the values being expressed in c.g.s. units. With such an arrangement, a smaller magnet can be employed than hitherto. Fig. 2 shows a magnet system in which the permanent magnet 9 has the shape of a rectangular parallelopiped and carries at its ends soft iron bars 10, 11 carrying polepieces 12, 13. The volume of the magnet, which is made of cobalt steel containing 6 per cent of cobalt, is 8À8 cubic centimetres. Figs. 3 and 4 show a modification employing two magnets 14, 14 interconnected by a bar of soft iron 15, each magnet being dimensioned according to the principle of the invention. Each magnet also acts as a polepiece being bent so as to form between the free ends 16, 17 an air gap in which the armature 18 is movably arranged.