Dynamic microphones operate very similar to a passive speakers, only in reverse. Instead of an electrical signal moving a speaker’s diaphragm to produce sound; sound is moving a diaphragm to produce an electrical signal. Inside the microphone’s capsule is a magnetic field that surrounds a small, movable induction coil attached to a diaphragm. When sound waves vibrate the diaphragm, it moves the coil which, in turn, creates a voltage induced by the magnetic field. That voltage is then increased by a transformer and sent to the microphone’s output jack.
Condenser microphones operate on the principle of variable capacitance. Let’s define capacitance as “the ability to store energy in an electric field between two conducting bodies”. The diaphragm of a condenser mic acts as one of the conducting bodies and when a sound wave vibrates it, the distance between the “two conductive bodies” begins to change. These tiny changes in distance vary the capacitance and, eventually, the output voltage of the microphone.
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