Condenser Mic
A condenser microphone converts diaphragm motion into an electrical signal through a changing capacitance. Its sensitive, high-impedance capsule needs suitable interface electronics. Frequency response, noise, maximum sound level and power requirements belong to the particular microphone, not to the word condenser.
The diaphragm and a nearby backplate form a capacitor. Sound changes their separation and therefore capacitance. In an externally polarized capsule, a bias circuit establishes charge, and the changing capacitance produces a changing electrical signal. Electronics close to the capsule buffer that high-impedance signal. Electret capsules provide polarization differently, and not every condenser microphone requires the same phantom supply.
In plain terms
Imagine a very light membrane facing a fixed plate. Sound nudges the membrane, changing the tiny gap; the electronics detect the resulting change in capacitance.
Why designers use it
- Sensing small diaphragm movements through capacitance.
- Selecting an appropriate microphone for recording, broadcasting or acoustic measurement.
- Combining a suitable capsule with low-noise interface electronics.
Best for
- Studio vocals
- Acoustic instruments
- Broadcast
Key specifications
- Capsule and power: Externally polarized or prepolarized; check the specified supply
- Acoustic performance: Sensitivity, frequency response, self-noise and maximum sound level
- Interface: Required input circuit and output impedance
When not to use it
- When the selected microphone cannot tolerate the environment or required sound pressure.
- When its required power and interface are unavailable.
- When a different microphone's directional response, handling-noise or ruggedness characteristics better suit the job.
Common mistakes
- Assuming every condenser microphone needs exactly 48 V phantom power.
- Connecting a capsule directly to a low-impedance input without the required interface.
- Ignoring the microphone's maximum sound level, sensitivity or self-noise.
- Connecting or disconnecting a powered audio system without following its muting and power procedure.
Where you will find it
- A studio microphone can use a condenser capsule and nearby buffer electronics to deliver a usable signal to an audio preamplifier.
- A measurement microphone must be selected and calibrated for its intended frequency and sound-pressure range. The sensing principle alone does not guarantee measurement accuracy.
A short history
E. C. Wente filed his Telephone Transmitter patent application on December 20, 1916. His diaphragm and backplate formed a variable capacitor. The Western Electric 47A of 1928 used his 394 capsule and was one of the first commercial condenser microphones, rather than an established first of every commercial design.