GB1121135A - Tapered spring reverberation delay line - Google Patents

Abstract

1,121,135. Reverberation systems. D. H. BALDWIN CO. 2 Aug., 1965 [18 Sept., 1964], No. 33019/65. Heading H4R. Delay device for a reverberation system comprises, Fig. 2, a spring 12 having tapered end sections mounted between input and output transducers 10 and 20, respectively. A signal applied to the coil of the input transducer imparts a torsional vibration to the annular permanent magnet 22 which vibration is coupled to the spring at 14. The torsional vibration. which is transmitted non-dispersively in the spring, is changed to a dispersive transverse vibration at a point in the tapered portion of the spring where the turn length of the spring is equal to a quarter wavelength of the torsional vibration of the spring. The transverse mode propagates to a corresponding point in the taper at the other end of the spring, where it is converted back to a torsional mode to be detected by the reproduce transducer 20, and also reflected by the mismatched termination to provide multiple delays. Due to the frequency dependent position of the mode change, and the dispersive transmission in the transverse mode, the delay produced by the device is dispersive, which is said to be desirable to avoid abrupt periodic reflections and severe flutter. The transducer hooks 18 and 19 are of low compliance, e.g. seamless tubing of cold drawn " Monel " (Registered Trade Mark), secured to the supports 30 and 32 by high compliance support wires 23, e.g. of small diameter beryllium copper or phosphor bronze, with vibration dampers 24 of butyl rubber. Fig. 7 shows the method of connecting the delay device 92 in the reproducing change of a source 85, e.g. an electronic musical instrument, phonograph, or tape recorder.