Ribbon microphone

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A Ribbon microphone is a type of dynamic microphone that uses a thin metal ribbon placed between the poles of a magnet and generate voltages by electromagnetic induction. Ribbon mics are typically bidirectional, meaning they pick up sounds equally well from either side of the microphone.

In the dynamic microphone, the diaphragm is attached to a light movable coil that generates a voltage as it moves back and forth between the poles of a permanent magnet.

Ribbon microphones generate voltages by electromagnetic induction; a current is induced at right angles to both the ribbon velocity and magnetic field direction. As the sound wave causes the ribbon to move, the induced current in the ribbon is proportional to the particle velocity in the sound wave. The voltage output of the ribbon is typically quite low compared to a dynamic moving coil microphone and a step-up transformer is used to increase the voltage output and increase the output impedance.

Ribbon microphones are generally the most delicate and expensive microphone. They are prized for their ability to capture high-frequency detail, comparing very favourably with condenser microphones, which can often sound subjectively "aggresive" or "brittle" in the high end of the frequency spectrum. Because of their bidirectional pickup pattern, ribbon microphones are often used in pairs to produce the Blumlein Pair recording array.

One of the first ribbon microphones was the RCA PB-31. Produced in 1931, it was a breakthrough technology in sound, and revolutionized the recording and broadcast industry, setting a new standard in frequency response. The clarity and realism were unmatched by any of the condenser microphones of its day.

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