GB460994A - Improvements in electro-dynamic sound reproducers - Google Patents

Abstract

460,994. Acoustic filters. JENSEN RADIO MANUFACTURING CO. May 3, 1935, No. 13250. Convention date, June 4, 1934. [Class 13] [Also in Group XXXIX] An acoustically - coupled network forming a low-pass filter is disposed in the hollow core 47 of the magnet of a moving-coil loudspeaker and comprises a chamber 67, formed below a dome 68 connected to the coil former, and in fluid connection with chambers 61, 60, 59 bounded by partitions 62, 63, 69 and by a closing member 57 secured to the housing 45 of the magnet. The terminal chamber 59 may be filled with felt, glass wool, or a similar material to increase the resistance at high frequencies. The chambers are connected by tubes 64, 65, 66 mounted in the partitions and the function of the arrangement is to impose a stiffness reactance which increases with frequency. The volume of the chamber 67 may be varied by adjusting the position of the partition 69. The Specification as open to inspection under Sect. 91 describes an arrangement, Fig. 15 (Cancelled), in which a chamber 247 having the diaphragm 243 as a bounding surface, is connected to chambers 252, 254, 256 formed by partitions 250, 255 in the casing and by the cone housing 245 of the loud-speaker. Connection between the chambers is effected by tubes 246, 253, 257, and the final chamber may be filled with sound-absorbing material. This subject-matter does not appear in the Specification as accepted, but is included in Specification 461,073.