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Re: Physics of moisture-induced mic noise

Subject: Re: Physics of moisture-induced mic noise
From: "Klas Strandberg" klasstrandberg
Date: Wed Jan 6, 2010 4:44 pm ((PST))
At 20:45 2010-01-06, you wrote:
>Richard Lee wrote that the gap in true condenser
>mics is sealed. Does this mean that no dirt or
>moisture can get into the gap?  Rob D.

All omnis are "sealed" between the membrane and electrode, but
still... I mean, I have seen camera lenses with mould growing between
two glued lenses.
Double membrane cardioids are "sealed" too, but - as omnis - must have a
small air-intake, a air pressure leveler," otherwise the membranes
will blow up and crack at a high altitude, even in a airplane.
Cardioids are "fully" open, as the sound must go through the sides of
the mic, through the electrode and backwards at the membrane, out of
phase. As I see it, cardioids must be the most exposed for dust and
other pollution, unless they are double membranes.

I'll have a chat with my friends about your "coping to humidity" topic.

Are you sure that the base response is the same after the "coping"?
My first thought was that the membrane slacks cause of humidity and
gets sucked against the electrode and that something happens then
that make the mic work, in a limited way, but without clearly audible
pops and noise.

Some studio mic=B4s behave that way if you blow into them. The membrane
gets stuck to the electrode and you must turn off the phantom power
for a minute or two, to make it go free again from the electrode and
get full base response.
That was one of the reasons why Neumann put a "screw in the middle"
of the membrane and made others follow. The one inch China mic=B4s I
have seen has been Neumann copies in that sense, as they are much
easier to make.

I=B4ll get back to you when we have discussed the "coping" matter. It
is interesting.


Telinga Microphones, Botarbo,
S-748 96 Tobo, Sweden.
Phone & fax int + 295 310 01

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