. Elements of acoustical engineering. Electro-acoustics; Sound. 234 MISCELLANEOUS TRANSDUCERS cross-sectional view and the equivalent circuit of a mechanical phonograph is shown in Fig. The system consists essentially of a diaphragm ruz coupled to a needle Cm\ driven by a phonograph record. To improve the radiation efficiency, the diaphragm is coupled to the horn Zmh- The record mechanical Zmr impedance is usually large compared to the impedance of the remainder of the system save at the high frequencies. The record. EQUIVALENT CIRCUIT en O30 / -\ Kr\ 1 > / >. f \ M] a 10 u V \ J C
. Elements of acoustical engineering. Electro-acoustics; Sound. 234 MISCELLANEOUS TRANSDUCERS cross-sectional view and the equivalent circuit of a mechanical phonograph is shown in Fig. The system consists essentially of a diaphragm ruz coupled to a needle Cm\ driven by a phonograph record. To improve the radiation efficiency, the diaphragm is coupled to the horn Zmh- The record mechanical Zmr impedance is usually large compared to the impedance of the remainder of the system save at the high frequencies. The record. EQUIVALENT CIRCUIT en O30 / -\ Kr\ 1 > / >. f \ M] a 10 u V \ J CROSS-SECTIONAL VIEW f HtuuLNi-r Fig. Cross-sectional view and equivalent circuit of a mechanical phonograph. In the equivalent circuit: Zmr the mechanical impedance of the record. Cmi, Cmi, Cms, Cui, Cui, Cui, and Cmi the compliances of the needle, the needle holder arm pivot, the needle holder arm, the connector, the spider, the suspension and the air chamber. m\, m^ and rriz the mass of the needle holder arm, the spider and thediaphragm. %mh the impedance at the throat of the horn, ju the force generated by a constant velocity generator. The graph shows the pressure response frequency characteristic of a console type mechanical phono- graph. (After Maxfield and Harrison.) mechanical impedance is a function of the type of material. Obviously, it is higher for the harder materials. The generator in the equivalent cir- cuit of this system is of the constant current type. That is, Jm delivers constant velocity to the equivalent circuit. That is, the velocity is indepen- dent of the impedance of the load. The velocity response frequency characteristic of a typical phono- graph record for constant voltage input into the microphone amplifier (see Sec. YIAF) is shown in Fig. To prevent overcutting the groove the system is compensated so that the amplitude for constant input is es- sentially independent of the frequency below 500 cycles. Therefore, the velocity under these
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