electret condenser?

[guhlenn]

could someone please explain the basic idea for the use of a elctret condenser mic. please?

greetz guhlenn

[ametth]

for recording sounds?

[skippy]

Do you mean "how does it work", with respect to an externally-polarized condenser mic? Or do you mean "what would you record with one"?

How it works is pretty simple. An electret condenser's capsule has a backplate and a diaphragm, pretty much like an externally polarized condenser recording mic. The capsule's capacitance changes with the pressure changes in the acoustic environment, just the same. However, instead of using the phantom power supply to bias up (or polarize) the backplate with repect to the diaphragm, an electret design uses a backplate with an electrostatic charge magically and permanently trapped on its surface. So the mic will still require a power supply, but it can be just one or two volts- just enough to power a single-FET preamp to convert the extremely high capsule impedance (a very tiny capacitance change) into a usable signal.

This can be very cheap to make, and that's usually the drawback of an electret. The interal preamp is usually minimal, since it does not have to power the capsule, and the lower-end mics are often little better than speech-grade. Any electret that is only powered by one or two AA cells will usually have very low acoustical headroom (a low overload threshold at high SPL), and fairly crummy noise and distortion performance.

However, it's not always true that *all* electrets have those drawbacks: the tiny Countryman electrets were some of my favorite drum and percussion mics, back in the day. I used to use the figure-8 version on congas, and slip the little thing right down between the hoops- and the cardioid kicked butt on sax, and you couldn't even see it in the bell... The headworn electrets used for live musical theatre are tiny enough to hide under stage makeup, and can sound absolutely killer- and cost a freakin' *fortune*. Generally speaking, as in all other things, you get what you pay for. The big advantage of professional-grade electrets is usually their miniscule size: great for sneaking into odd spots, and especially for presenting a very low visual profile for live work. In the studio, there's usually a better-sounding choice in a larger package, but every mic has its place...

If it can be powered with +48v phantom, it's probably useful for _something_. Exactly what mic did you have in mind, and for what application?

[guhlenn]

hi skippy,

thanks for answering and well, i was wondering most about HOW it works but any oiptions for use are welcome. No it's a sony ECM 220. it's like from the 60/70 and we bought it for $15. figuring that if it were crap we could still use it to create odd and distorted vocals. it has a normal penlite in it and is about 3/4 of a sm57 in size. it's so old it's got a cable with a 3 pin DIN plug at the end. The guy we bought it from told us it had been very expensive when he bought it but didn't have a clue now what it could be worth.

thanks man, any help is welcome!
greetz guhlenn

and ammeth, you're sooo wrong.

[ametth]

dammit!! can noone spell my name right?

[guhlenn]

oooooooooohhhhhhhhhhhhh

i'm sooo sorry, ametth. in fact i just spelled it wrong again, but as i know i'm stupid i checked it so...

if it makes you feel any better; people tend to forget my second 'n' a lot...

greetz guhlenN

[skippy]

Hmm. I actually have a vague recollection of that mic from way back when, but only very vague- I think one of my old collaborators had one... A quick Web search indicates that it is moderately popular among the concert bootleggers as an easily-concealed recording mic, and that it currently sells for around $50.

Is it a stereo mic, by any chance? Since the bootleggers list it as a common mic in that use, I would suspect so. And that might explain the odd connector as well (2-channel single-ended output, as opposed to one balanced mono output). If it is stereo, it's probably a mid-side design. And as such it'd probably be interesting for overheads, room ambience, and so on. If the bootleggers like it for making their illegal tapes of live shows, it might not sound like complete trash (although the caveat about high-SPL distortion still applies, with that 1.5v supply).

The problem is that Sony has used the "220" model number too many times on their mics- there's the old C-220, which is an '60s tube muc, their current FV-220, which is a low-end dynamic... The ECM-220 is definitely an older, out-of-production mic, and I don't see it listed on the equipment lists of any current studios (although a concert hall in Australia lists two of them on their gear list), but that doesn't mean a dadgum thing.

Come to think of it: if it is a M/S stereo mic with two single-ended outputs, you could probably get a *very* odd sound out of it by running one to pin 2 and one to pin 3 of a normal balanced input... It might not be a _useful_ sound, but it'd be unusual, for sure. You might actually like it, especially if the vocalist moves around a lot as he sings. This would be an amusing workout for the mic preamp, too, because the vast majority of the signal would be common-mode. Different preamps will do different things with this: a low-end transformerless preamp will give you a radically different sound than a transformer input stage.

Let your ears be the judge. Hang it, experiment, see how it sounds, and have fun! Some of the best special-purpose mics I had for my old studio came from pawnshops, bought on a lark, and I'm still kicking myself for having sold them...

[guhlenn]

thanks skippy, your've been very helpful!

i'll let you know when i heard it. no indivcationon the mic itself that says stereo....


thanks!\
guhlenn

[Exterminator]

I purchased 2 of these new in 1977-1978. They are great for voice recordings or amplification. Their frequency response is 50-12000 Hz. There are two output impedance settings, 10 or 200 ohms. The impedance setting may be changed by re-soldering the jumper at the base of the battery compartment. They are shipped from the factory with the setting at 200 ohms. If you are going to connect them to a soundboard, I would suggest changing the setting to 10 ohms. I have used them both indoors and outdoors with good results. I used mine on a fairly regular basis until a few years ago. They still work well after 30 years. That says something for the quality. I hope this helps.

[mrmoe]

I have used the Sony ecm-22p mics for recording acoustic guitar and have had good results.....these mics have been in my collection since the early 70's...