GB1072411A - Improvements in or relating to delay devices for producing artificial reverberation - Google Patents

Abstract

1,072,411. Artificial reverberation devices; transducers. AKUSTISCHE U. KINO-GERATE G.m.b.H. Dec. 31, 1963 [Jan. 18, 1963], No. 51416/63. Headings H4J and H4R. In an artificial reverberation device, a plurality of helical springs of different diameters are arranged one inside the other. At one end they are connected to a common electromechanical transducer and at the other end they are connected to a common mechanico-electrical transducer. Preferably the ratio of the delay times associated with each pair of springs is an irrational number. Compressional vibrations are imparted to three helical springs 5 (Fig. 1), by a transducer unit A including an exciter coil 1 which energizes a magnetic circuit 2 when an audiofrequency signal U IN is applied. A bar magnet 3 is accommodated in an air gap and is connected by a stiff spring 4 to the unit housing. The pick-up unit B is similar. The springs 4, 4<SP>1</SP> being stiff, vibrations imparted to the springs 5 reciprocate repeatedly between the ends until they decay. Flexural (transverse) vibrations may be obtained if the springs (4, 4<SP>1</SP>) are leaf springs, Fig. 2 (not shown). Torsional vibrations may be obtained by use of diametrically magnetized permanent magnets (3, 31, Figs. 3, 3a, not shown), of cylidruical form. The springs 4, 4<SP>1</SP> may be leaf springs or helical springs. The entire system may be damped by immersion in oil. Felt damping material (6, 61) may be inserted between each permanent magnet (3, 3<SP>1</SP>) and its associated magnetic circuit (2, 2<SP>1</SP>). A plurality of such delay devices may be arranged in series, Fig. 4 (not shown), or in parallel. The drive unit for producing torsional vibrations may comprise a rotating coil transducer. Another torsional unit uses two concentric delay springs (5<SP>1</SP>, 7), Fig. 5 (not shown).