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Re: Physics of moisture-induced mic noise (was MS-stereo and figure-

Subject: Re: Physics of moisture-induced mic noise (was MS-stereo and figure-
From: "Dan Dugan" dandugan_1999
Date: Sun Jan 3, 2010 4:16 pm ((PST))
> (1) Audio Technica describes the AT-3032's element as, "fixed-charge back=
> permanently polarized condenser." I asked this
> before and I don't recall an answer, is this an
> electret mic capsule, not a "true" condenser? I
> think the Sennhesier ME series mics might fall
> into this category too.

I think when people say "true condensor" they mean "high-voltage externally=
-polarized condensor." Such mics can be quieter and have higher sensitivity=
. Typically a manufacturer's top line will be high-voltage condensors, and =
their mid- and low-priced lines electrets. Yes, the ME-series is electret.

You know how sometimes a piece of plastic can get charged, you keep wiping =
dust off it and it keeps attracting it back? That's the principle of the el=

> If so, its
> well-documented that recordists can get moisture
> related issues with all of these mics--
> especially in the first several hours of
> operation under provoking humid conditions.

In my experience electrets are a lot less sensitive to humidity, but one or=
 two of my 3032s have been screwing up while left out overnight--last exped=
ition I had to get out of the sack just before dawn chorus to swap one that=
 was motorboating. Brrr. But three of the four were fine!

>  Its rare for recordists to
> leave mics on and outdoors continuously, but it
> occurs to me that one could actually study the
> duration-induced phenomenon, maybe with a
> microscope of some capsules, to find out what is
> producing the physical change and build this
> "change" into the mic at the outset. Maybe one
> could "see" the discharges with the right tools?
> I have no idea about the science that would be
> involved but I thought it might be worth
> mentioning again.

My easy test is to pop them into the refrigerator (not the freezer) at arou=
nd 40 degrees F and listen. It can be only a few minutes before a susceptib=
le mic can start making noises. BTW when you have sets of identical things =
it's important to label them all so the individuals have identity.

It seems obvious but I didn't know till recently that the 3032 capsules uns=
crew. I think when I tried to unscrew my first one and it didn't budge I as=
sumed that they didn't. Now I have to label both the capsules and the bodie=

-Dan Dugan

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