A condenser microphone uses a capacitor to convert the compression and rarefaction of sound waves into electrical energy. Condenser microphones require power (voltage) in order to operate.
Condenser microphones use a pair of charged metal plates, one fixed (the back plate) and one movable (the diaphragm), forming a capacitor. When a sound wave hits the diaphragm, the distance between the two plates changes which produces a change in an electrical characteristic called capacitance. It is the variation of the spacing, due to the motion of the diaphragm relative to the fixed back plate, which produces the electrical signal corresponding to the sound picked up.
To obtain a signal, condenser microphones require an electrical current to charge the plates. This is usually provided either by a battery or is sent down the microphone cable itself. This latter method is known as phantom powering. Most condenser microphones can operate with phantom power voltages ranging from 11 to 52 VDC, and is usually provided by the mixing console/audio interface.
Key advantages of a condenser microphone:
- The diaphragm assembly is light compared to that of dynamic microphones, hence is more efficient at moving and is capable of capturing a range of high frequencies
- Easy to obtain a flat frequency response and extended frequency ranges
- Can be small in design
Key disadvantages of a condenser microphone:
- There is a limit to the maximum signal level the electronics can handle
- They are more complex than dynamic microphones and tend to be more adversely affected by extremes of temperature and humidity
- Cheaper models can produce a small amount of noise from the electronics
In general, condenser microphones are more expensive than dynamic microphones but are more suitable for capturing the sounds of acoustic instruments and vocals due to their high sensitivity. They should be avoided when dealing with high sound pressures, such as that created from a kick drum.
The sound produced from a condenser microphone can be described as being crisp, clear and detailed. Often the sound quality is better than that of a dynamic microphone.