Hello Everyone,
What are the physical principles behind why are condenser microphones
are adversely affected by high moisture? Is it a matter of humidity,
condensation, moisture absorption, or some other factor? Why does it
create crackling noises? Are there any design questions or specified
ratings that can be asked of a manufacturer to characterize this?
Perhaps in terms of maximum guaranteed operating (not storage)
humidity at a particular operating temperature, or temperature
range. Is moisture the basis of issues pertaining to operating at
cold temperatures?
These are the thoughts I captured from the groups archives:
It appears that the result of operating in a moist environment for
some length of time can result in sporadic crackling noise in the
output. The effect is completely harmless to the mic and fully
reversible by relocating the mic to an environment of lower moisture
for some period of time.
Packets of silica are effective for drawing moisture out of the mic
and in keeping it from entering when in storage. Sealed containers,
such as homemade ones built from PVC pipes, "Pelican Products" style
gasketed cases or alternately Zip-Lock bags are also effective.
Minimizing the amount of sealed air around the mic can prevent or
minimize condensation from forming when the mic is brought from a
cold environment back indoors. In this case one would not open the
sealed bag or compartment until the mic warmed to ambient
temperature.
Slightly elevated ambient temperature can accelerate drying time. Of
course it would be necessary to observe either the mics maximum
operating or storage temperatures. Probably might help starting off
on the warm side when beginning to record in a cold environment (i.e.
bring mics indoors rather than leaving them in the car in the
winter). But this leaves me wondering about the whether one could
hear any effect of drifting temperature on the mic characteristics?
Perhaps it would be better to let the mic acclimate to the cold
first? Of course you might consider keeping the batteries warm until
just before use.
Pouches of Silica of course, requires periodic drying in an oven
(several hours at 225 to 275 degrees F, depending on mfg.'s
recommendations) when it becomes saturated. Silica can be purchased
incorporating an indicator which changes color when the media
requires drying.
Apparently the susceptibility to moisture varies between mic
manufacturers and the group's experience vouches that the Sennheiser
K6 and MKH are field proven to perform better than most. Better than
what, I'm not exactly certain. Telinga products appear from the
posts to be slightly more sensitive to moisture in contrast to
Sennheisers.
Did I miss anything or are any of my thoughts wrong?
Brian Bystrek
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