GB489588A - Improvements in or relating to sound-translating devices - Google Patents

Abstract

489,588. Acoustic filters and resonators. STANDARD TELEPHONES & CABLES, Ltd. July 30, 1937, No. 21186. Convention date, Sept. 2, 1936. [Class 13] [Also in Groups XXXIX and XL] Relates to an acoustic translating device, such as a loud-speaker or microphone, in which a diaphragm forms part of the surface of an enclosure, the interior of which is connected to the outer air by at least one tube providing a column of air which forms an acoustic mass constituting part of a low-pass filter for the air vibrations from the back of the diaphragm, as described in Specification 382,268. According to one feature of the invention, an acoustic resistance element is positioned across the passage through at least one tube ; according to another feature, at least one tube is increased in cross-sectional area over an intermediate portion of its length to form a resonance chamber. One or more of the tubes may be of triangular cross-section, and when the loud-speaker forms part of a cabinet radio set, a horizontal partition may be placed across the cabinet above the chassis of the receiver. As shown in Fig. 3, the inner ends of tubes 10, 11 mounted in the front wall of a cabinet 9 are associated with adjustable cup members 13, 14 forming chambers 15, 16. In a modified arrangement, Fig. 4, the inner ends of the tubes 18 .... 21 are perforated and co-operate with adjustable resistance members constituted by plates 181..21<1>. Partitions 25, 26 located above the receiver chassis 12 are formed with apertures 28, 29 and the space between the partitions may be connected by tubes to the space above the partition 25 and/or to that below the partition 26. The triangular tubes may be disposed in the spaces between the rim of the loudspeaker and the corners of a baffle-board, Fig. 1 (not shown), and one or more tubes may be formed with an enlarged central chamber connected to the ends by portions having a constricted cross-section, Fig. 5 (not shown), which may be adjustable. The Specification as open to inspection under Sect. 91 includes an arrangement, Fig. 4 (Cancelled and not shown), in which a single tube is disposed in the rear wall of a cabinet enclosing a receiving chassis and having a loud-speaker mounted on its front wall. This subject-matter does not appear in the Specification as accepted.