GB263189A - Loud speakers - Google Patents

Abstract

263,189. Saldana, F. Dec. 17, 1925, [Convention date]. Loud-speakers; magnetic instruments; diaphragms. - A loud-speaker is provided with an asynchronous vibrating reed built up of a central portion, constituting or attached to the armature of the electromagnetic unit, and a number of radial arms of different natural frequencies supported at their outer ends by the casing for the electromagnetic unit. The reed may be connected with two conical diaphragms having their apices towards one another, the diaphragms having different natural frequencies. Fig. 3 shows a vibrating reed made up of three branches 3, 4, and 5 extending from the centre part 1 which, in this construetion, forms the armature of the electromagnet. The branch 3 is thinner than the branches 4, 5, whilst the branch 4 is of less width than branch 5. Other constructions of reed are described in which the armature 1 forms the centre of the four arms of a cross and in which a plate is divided by radial slits, the several parts thus formed being of different thicknesses. The reed is mounted on a casing 15, Fig. 2, the electromagnetic system 2 being mounted on a plate 16 to which is attached a stem 17 extending through a long sleeve 18 and threaded at its outer end to receive a nut 21. A spring 23 presses the electromagnet towards the armature 1, the distance between the two being regulated by rotation of the nut 21. Fig. 4 shows a construction of loud speaker in which two conical diaphragms 7, 8 tensioned in frames 11, 12 and having different natural frequencies of vibration are employed. The inner ends of the cones are closed by plates 10 secured to the stem of the reed armature by nuts 9. The diaphragm 7 is tensioned by means of leaf spring 16 and screw 17 whilst the diaphragm 8 is tensioned by means of the nuts 9. The diaphragms may be made of celluloid or similar products based on acetate or nitrate of cellulose or from paper or fabric coated with celluloid. The celluloid is moulded hot into the form shown and may have finely divided metal embodied therein. The thicknesses of the diaphragms preferably diminish progressively from the periphery towards the centre. The diaphragms may also be composed of more than one material, e.g. they may have a zone of thin wood next the periphery extended to the centre by a thin sheet of celluloid. A further form of loud speaker is shown in Fig. 5 in which the receiver casing 15 is mounted on a wooden sounding board 14 secured within a wooden frame 13.