Have you ever wondered how a small lapel mic or even a headset mic works? I haven't. I mean I have, but I haven't. Its magic I suppose or perhaps little sound elves in there change what I say into what the other end hears. Small little devils aren't they in yet they can perform about as good as my pro condenser mics. But how does it happen?
I recently bought a small SYNCO shotgun mic that was battery powered to use as an omnidirectional mic. Mind you, I knew it wasn't going to be the greatest mic in the world and certainly wasn't going to replace my expensive RØDE or even my TZ Audio Stellar X2 mic. I mean, how could it. Look at that tiny thing. It certainly didn't have the kind of condenser element that these larger mics have.
I even bought a cheaper lapel mic that I can use to record just me at close range and it does a fairly decent job. Then again, how can something the size of an oversized pencil end record anything with any quality at all? Truth is, there is little quality with some cheaper ones, but there are professional mics that employ electret elements that do a pretty darn good job.
Case in point. I watch Youtube videos by a couple of commentators (names withheld). I see them at their desks with condenser mics like I have and all the setup and I so want to know how they get such good sound in a non-studio like theirs. No way. So I took a closer look. I'll be danged. They are using a lapel mic. It's right there in front of me. But the sound. Nice!I had no idea.
Ok, Get To It. What About Electret Mics...
So that leads me back to the original question. With an electret element, how does this happen? Well, the answer isn't as elusive as I think. Here's what happens:
An electret mic; the element that is in a lapel mic, a headset mic, or basically any small microphone is, well, a condenser microphone. Yeps. Just like my RØDE or TZ. Well, almost. I mean, the basic principle is the same. Now from here on it might get technical but I'll try to give a simple description first.
A condenser mic is basically a device that has two metallic surfaces closely placed to one another but not touching. Each has some electric charge and when sound causes one to vibrate, it changes that electric charge or current. This is picked up by a bunch of specialized electronic components of which I have no idea what they do, and is amplified and converted to, well, recordable sound.
Think of it like folding wax paper around a comb and making a paper kazoo. Kinda fun. You should try it. That being said, the principal that causes the wax paper to vibrate and create a sound is the same principle that allows the mic to create a recordable electric current. Remember, your recording software needs some signal to record from whether it's a tape recorder or a digital workstation.
Oh Great. Here Comes The Classroom Part...
Now for the technical part. If you want to skip this and go to the next bolded section, no worries.
The basis of a condenser microphone is its condenser element. Usually this is a device that has metal rings and plates with some sort of gold or metallic plated mylar foil stretched across the front. A 48V charge is needed to supply the condenser with enough electrical current to function.
Now before I go on, let me explain condensers. I'm gonna try to make this simple because condensers aren't simple. Well, they are, but the concept makes no sense. See, a condenser; or what we call now a capacitor is a device that can hold a charge and/or in the case of the condenser, can vary the charge it keeps. Much like the paper kazoo varies the sound when activated, the condenser will vary the electrical current. This is VERY useful as electronic devices really can't hear.
Why do we call them condensers rather than capacitors. I don't know, but somewhere along the way, the terminology changed. But back to the condenser elements.
As mentioned, the condensers need 48V. That's why you have to supply phantom power to a mic. It has to have that or it doesn't work (believe me, that stymied me until I realized I didn't have it switched on).
Jeepers. I Thought We Were Going To Talk About Electret Mics Dude...
Ok here it is and I had no idea. I thought electret mics were just some cheap way to get sound and certainly NOT like my expensive condenser microphones. Little did I know, I was wrong. Actually thought I was wrong, but I was mistaken (see the joke there!) Anyhow, an electret mic works really in the same principle as does a 'condenser mic'. The only real difference is that it has a magnetically charged plate that when the magnetic field is disturbed - say by a metallic diaphragm, it will produce a signal. Kinda like what happens in a metal detector. Here is a really great explanation of exactly what goes into an electret mic. Its technical, so I have to warn you right now, pack a lunch (and a xanax).
about actual size (or smaller)
All In All...
Electrets are also small, hence the reason you can pack one into a small shotgun mic, a headset, a telephone, a hearing aid and so forth. Because they can do what they need to do without the need for large enclosures. They can be teeny tiny in fact.
One closing fact to note is that electret mic elements have a very different dynamic response than does the larger, more professional condenser mic elements to. Whereby the typical pro mic condenser can capture a frequency range of 20Hz to 20kHz, the typical electret element has a much less dynamic range, ranging from about 100Hz to 15kHz range with a much more pronounced midrange and high end. Which is why they are used in so many small electronics and why they sound tinny.
Typical electret mic frequency response
Typical RØDE mic frequency response