What’s an Electret Microphone

If you’ve been flipping through our range of microphones, you’ve probably come across the terms ‘electret’ and ‘true condenser’. But what’s the difference? And are ‘real’ condenser microphones always better than electret microphones, like the name suggests? In this blog, we’ll explain it all.

Electret Microphones: They’re Everywhere
What’s an Electret Condenser Microphone?
True Condenser
The End of the Electret Microphone?
See also…

Electret Microphones: They’re Everywhere

You can find electret microphones everywhere: in your phone, in your laptop, in the intercom system of your flat, and even the walkie-talkie that you see cops barking into in every action film ever only works because of an electret microphone. So what are they? Electret microphones are relatively cheap to produce and can be as small as you need them to be, which is why clip-on microphones and headset microphones also belong to the electret family. However, while the electret microphone is a kind of condenser microphone, they are slightly different.

What’s an Electret Condenser Microphone?

The difference between a normal condenser microphone and an electret microphone lies in the way that the electrical field between the diaphragm and back plate is generated. With a standard ‘true condenser’ microphone, this happens via an external power source which will usually be phantom power (so the 48 Volt phantom power supplied by most of the microphone inputs of mixers and audio interfaces). With an electret microphone, the back plate and diaphragm are both coated with a thin magnetic layer so it requires no external power source to generate an electric field. Another term for an electret microphone is a ‘permanently polarized condenser’ or ‘permanently biassed condenser’. However, electret microphones do feature an internal preamp, which does need power – but just a couple of volts. As such, electret condenser microphones can easily be powered by a battery or the input of your phone, laptop or camera.

True Condenser

The sound of early electret microphones left a lot to be desired. This was mainly because the magnetic layer made the diaphragm a lot thicker than the diaphragm of a condenser microphone. The result was dull and dead sound and a really low sensitivity level. At some point, the magnet would also wear out altogether and at that point, the microphone was dead forever. Because of the bad reputation of first-generation electret microphones, companies that manufactured high-end studio microphones were forced to distance themselves from the ‘electret family’. How did they do it? By introducing the ‘true condenser’.

The End of the Electret Microphone?

Since their first shaky incarnations, electret microphones have come a long way, one of the milestones being the ‘back electret’, where the backplate is magnetically charged, leaving the diaphragm free of any magnetic coating. Ever since this development came about, electret microphones could be fitted with the same ultra-thin diaphragms as the ‘true condenser’ variants. Names like DPA, Audio-Technica and AKG make high-quality electret condenser microphones that are just as good as so-called ‘true condenser’ microphones. Meanwhile, Neumann still swears by true condenser microphones, simply because the technique makes it easier to fabricate the frequency response, which is an essential feature of matched pairs.