Consumer Electronics

RIBBON (VELOCITY) MICROPHONES

With these microphones, the sound operates the transducing element directly without the use of a cone. A ribbon of aluminium foil, corrugated to allow backward and forward motion, is mounted edgeways between two pole-pieces [Fig. 2.12(a)]. We have here, then, the classic example of electromagnetic generation, a single conductor moving in a powerful magnetic field. There is no multiplication of induced emfs by the successive turns of a coil, the ribbon can be regarded as a coil with but a single turn. As a result, the output voltage is very low and so also is the impedance, something of the order of 0.1Ω. All ribbon microphones, therefore, have a built-in transformer to step-up the impedance and voltage to a usable ...