Microphones

Dynamic microphone

Most of you will have used a dynamic mic at sometime or another -- if it looks like a mesh ball on a stick, then it's almost certainly a dynamic model. In live sound, nearly all the mics used are dynamics, and in the studio, instruments such as drums, electric guitars, and basses may also be recorded using dynamic mics. Dynamic microphones have the advantages of being relatively inexpensive and hard-wearing, and they don't need a power supply or batteries to make them operate. So, how do they work?

Capacitor microphone

Capacitor mics have been around for several decades, and although modern capacitor mics do incorporate a few small technical improvements, the sound character has actually changed very little -- some of the best-sounding models were designed over 20 years ago. Basically, the heart of any capacitor mic is a pair of conducting plates, one fixed and the other in the form of a moving diaphragm. When the spacing between the plates changes (as it does when the diaphragm vibrates) the capacitance varies, and if a fixed electrical charge is applied to the capacitor, an electrical signal is produced which faithfully represents the diaphragm vibration.

electret microphones

There is another type of capacitor microphone, known as the electret mic. Despite inauspicious beginnings, these have now been developed to the point where they can rival true capacitor quality for a much lower price. Instead of applying an electrical charge to the microphone capsule via an external power source, electret mics use a diaphragm made from an insulating material that has a permanent electrical charge. A preamplifier is still needed, but this can be built very cheaply, and will run from a battery in some cases.