SE309609B - - Google Patents

Abstract

950,675. Transducers. SIEMENS & HALSKE A.G. July 19, 1961 [July 22, 1960], No. 26230/61. Heading H4J. An electro-acoustic transducer having a diaphragm is provided with a resonator in the form of an acoustic pipe disposed in front of the diaphragm, the pipe having an arcuate axis lying in a plane parallel to the diaphragm. As shown, the invention is applied to a moving- coil transducer having a moving coil 6, operating in a ring-shaped gap 5, mechanically connected to a diaphragm 7. The protective cap 8 has acoustically inactive apertures 9. An absorption resonator 10 is provided behind the diaphragm 7, the partition 11 being thin-walled and having two tubular resonator apertures 12, 13, of negligible acoustic frictional resistance, closed by foils 14, 15 of acoustic damping material. Apertures 16 in the pole plate 4 allow the resonator 10 to be directly coupled to the space behind the diaphragm 7 by the apertures 12, 13, and thus to suppress an undesired resonance point of the transducer. A tube 19 in the freely moving part of the diaphragm 7 couples the space in front of the diaphragm to that behind it, and is so dimensioned as to resonate at the lower frequency end of the frequency range, thus extending the said range. The provision of the two resonant pipes 21, 22 in front of the diaphragm serve to suppress resonant points at the higher frequency end of the range, the lengths of these pipes being chosen so as to be equal to half the wavelengths of the undesired resonant frequencies. In a modification, the pipes are disposed on the front surface of the diaphragm.