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5 - ELECTROMAGNETIC AND ELECTROSTATIC TRANSDUCERS

5.2 - THE ELECTROMAGNETIC RIBBON TRANSDUCER

In this type of microphone, the ribbon acts both as diaphragm and conductor. The horizontally corrugated ribbon, made of very thin aluminium foil, is clamped at both ends and suspended in a strong magnetic field provided by a permanent magnet as shown in Figure 17. Movement of the ribbon within the magnetic field will again generate an electromotive force proportional to the velocity of movement.


Figure 17 - The Magnetic Circuit Design used in the Coles 4038 Ribbon Microphone
The ribbon may also be corrugated only at the ends, whilst some form of vertical stiffening or vertical corrugations are used to facilitate a piston-like movement at right angles to the ribbon surface, as shown in Figure 18.



Figure 18 - The Magnetic Circuit Design used in the Beyer M260 Ribbon Microphone