What Are Electret Condenser Microphones?



We see many very cheap microphones listed as condenser microphones. Sometime the description includes the term "electret". What does that mean?


That they’re dangerous? Studio microphones often advertised as “true condensers”. What does that mean, and is there such a thing as “false” condenser microphones?

No, microphone electronics can only sense this capacitance change, if the condenser capsule is charged or “polarized” with a voltage. For good sensitivity, this polarization voltage must be fairly high.

There are two ways to apply this electric charge. The traditional way is to polarize the capsule with an external voltage. In studio applications, that’s no problem. The standard powering system is P48 Phantom power, which delivers 48 volts – enough to polarize the capsule, although many modern condenser mics contain voltage converters for even higher voltages (usually 60-80 volts)

Another polarization method is to “freeze” an electric charge permanently in the capsule. This is done by applying a special substance called “electret”. The term “electret” was coined, because it is the electrostatic equivalent of a permanent magnet. Usually, the electret film is applied to the capsule’s backplat
The fact that electret condenser capsules are more likely to be found in lower end products gave this technology a questionable reputation. Also, some early electret condensers went dead after a few years, because they lost their electric charge.

As a reaction, the term “true condenser” was coined for externally polarized capsules to differentiate them from presumably lower quality electret condensers. But that’s a marketing term. Technically, there is no such thing as a “false” or “untrue” condenser capsule
Electret condenser capsules don’t have to sound bad; nor do modern specimens lose their electric charge like some of their ancestors of the 1970s did. A number of reputable manufacturers are convinced enough of electret condenser technology to employ it in their top-of-the-line microphones, some of which costing more than $ 2000
Good sound is not simply the result of a particular polarization scheme. Superior sound quality comes with great engineering and high attention to detail in manufacture.
Just in case you’re wondering: All Neumann condenser microphones use externally polarized “true condenser” capsules.