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Author Topic: How To Keep A Condenser Capsule Clean and Dry  (Read 38894 times)

Klaus Heyne

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How To Keep A Condenser Capsule Clean and Dry
« on: May 07, 2004, 06:01:07 pm »

How to keep a condenser capsule clean and dry

Preventative maintenance of condenser mics is such an important topic and often so easy to do, that I ask you to read the following, and add your own tips to it. It may save you money over capsule restoration or replacement!

Quote:

 Wouldn't a wind-screen do the job?

It would do an excellent job to keep microphone specialists employed with capsule cleaning jobs!

Please use wind socks/screens only when nothing else will do to prevent popping or wind noise from exciting the capsule. Wind socks are made of open-cell plastic foam which starts deteriorating within 1-2 years after manufacture; thereafter its disintegration accelerates.  Fine foam dust and flakes will quickly penetrate through the screen and be deposited all over the (electrostatically charged and therefore attractive) capsule area. The final stage of this material is that of a semi-liquefied goo, and then the fun begins...

Try this test with your windscreen: rub your fingers against it over a white piece of paper. If foam dust is deposited on the paper, throw the screen away. It will be harmful to the capsule, and be more costly to use than to replace.
                                           --------------------------------------------------

The best, cheapest (free) and all around easiest way to preventing a condenser capsule from deteriorating is the good old plastic bag from your supermarket's produce or cereal/candy department (you may have to look a little harder for a bag that is made of a bit thicker plastic material, but it will last longer.)

Just put the bag over the mic on the stand, if you cannot tear down the recording set up for positioning reasons. Then, after the session is finished, permanently store the mic in this bag inside its proper case. No need to seal the bag tight.  You can let the mic breathe.

If humidity in the room was excessive, you would already have had moisture back- down on the capsule, so no need to worry if the bag fits too tightly. If anything, a bag over a warm tube mic will force redistribution of the higher humidity sitting on the capsule towards the drier amp region of the mic, so the bag will somewhat act as a capsule dehumidifier.

The main idea of the bag over the capsule is that of a physical barrier- to prevent the electrostatically attractive capsule from sucking in particles from as far as six feet away, and letting these contaminants act like salt crystals which catalyze fog formation: If there is any amount of a dirt layer, it becomes that much easier for moisture to form droplets and start a conductive path to short out the two plates of the condenser (diaphragm and backplate.)
                                                 -------------------------------------------

Silica-Gel bags are an excellent way of drying an overly humidified capsule, but only if you tightly restrict the volume of humid air getting to the moisture-hungry silica crystals.

Placing a silica bag next to the mic grill without otherwise restricting its access to air may be well intended, but is useless: Silica is so hygroscopic that any access to unlimited amounts of air will neutralize the silica within minutes.  

So here, then, is the proper way to dehumidify a condenser capsule:

First, dry the Silica bag as directed, usually printed on its side. I place it in a conventional oven or toaster oven, set to ca. 350-400
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Klaus Heyne
German Masterworks
www.GermanMasterworks.com

John Etnier

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Re: How to keep a condenser capsule clean and dry
« Reply #1 on: May 21, 2004, 09:59:13 am »

Until reading this sticky on capsule cleanliness I had regularly used the original-issue foam windscreens on a pair of Neumann KM-84's.

In some circumstances the guitarist will inadvertently breathe into the mics (rear ports?), causing a big LF noise. The foam filters eliminate this problem, whereas a hoop-style pop-screen doesn't really work because it gets in the way of an already crowded situation, particularly when the guitarist is singing and playing.

Any problems with that?
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Klaus Heyne

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Re: How to keep a condenser capsule clean and dry
« Reply #2 on: May 21, 2004, 01:17:50 pm »

John,
I understand that some circumstances require the dreaded windscreen/sock.

Use your foam screens until they don't pass the rub test anymore, then buy new ones, and test regularly.

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Klaus Heyne
German Masterworks
www.GermanMasterworks.com

bgavin (Bruce Gavin)

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Re: How to keep a condenser capsule clean and dry
« Reply #3 on: May 27, 2004, 10:03:00 am »

Klaus Heyne wrote on Fri, 07 May 2004 15:01

...(electrostatically charged and therefore attractive) capsule area.


Does this imply electret capsules attract dust at all times, compared to externally polarized types only when they are active?

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sgoebel

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Re: How to keep a condenser capsule clean and dry
« Reply #4 on: June 12, 2004, 10:05:03 am »

Considering your comments on the deterioration of foam material in windscreens, do you recommend against using an original wood box for storage if the interior is made of "hard molded foam"?

TIA,
Stephen Goebel
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Klaus Heyne

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Re: How to keep a condenser capsule clean and dry
« Reply #5 on: June 14, 2004, 12:26:12 am »

For form-fitting foam lined microphone cases the same rules apply as for the wind screens:

Once the foam visibly flakes off when rubbing it hard, it's time to at minimum use a particle barrier (i.e. plastic bag) to prevent the foam particles from hitting and melding onto the capsule.
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Klaus Heyne
German Masterworks
www.GermanMasterworks.com

djosephson

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Re: How to keep a condenser capsule clean and dry
« Reply #6 on: July 27, 2004, 04:55:59 pm »

Quote:

Klaus Heyne wrote on Fri, 07 May 2004 15:01
...(electrostatically charged and therefore attractive) capsule area.


and bgavin replied:

Quote:

Does this imply electret capsules attract dust at all times, compared to externally polarized types only when they are active?


First, the electrostatic attraction is only part of the [foam generated] problem. Even those capsules with no electrostatic attraction have the same problem, because the foam dust itself is generally charged and sticks to everything.

As far as electostatic attraction, it very much depends on the specific capsule.

I know of no modern electret capsules that have the charged surface exposed to the outside air (but, see above, it doesn't matter). Externally polarized types may have the diaphragm surface at or near ground potential or at high voltage (40 to 100 volts). My personal opinion is that makers of capsules with diaphragms at ground potential have made too much of the "electrostatically charged and therefore attractive" issue. The foam dust that Klaus refers to is already electrostatically charged and will attract itself to anything.

The worst problem with airborne junk like foam dust is that the particles become coated with all sorts of conductive dust from the air, and the foam dust becomes the glue to stick it to everything.

In my view, loading junk on the diaphragm surface is not so much a problem on the conductive surface of the diaphragm, but rather on the insulating surfaces (of the diaphragm, between the metallized portion and the support ring, and on the solid plastic parts of the capsule too). Just a tiny amount of this stuff will make the capsule moisture sensitive, noisy, or intermittently dead.

(See Also Sticky "How To Test A Capsule For Contamination Defects"                      K.H.)
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Alécio Costa - Brazil

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Re: How to keep a condenser capsule clean and dry
« Reply #7 on: August 18, 2004, 07:16:56 pm »

I recently bought an AT 4040 which came with a black piece of velvet with their logo.

I have to confess that at first I thought it was a child's hat. Is it good for protecting the mike while on stand?
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Klaus Heyne

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Re: How to keep a condenser capsule clean and dry
« Reply #8 on: August 18, 2004, 10:09:04 pm »

If the velvet you mention is of the lint-free variety, as used also on some Neumann products in the past, you are fine.

To find out, make the test: rub the velvet over a white piece of paper, and examine, whether any particles have gathered on it. Bill Fosbury, who owns an AT 4050 with velvet bag was surprised to find 1/2 mm wide lint particles. He adds: "Inspect the (white examining) paper with an 8x or greater magnifying glass."

Regarding mold forming on plastic: I refer back to my method of avoiding any of this: plastic bag over the mic. Period. That way, it does not matter what's underneith.
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Klaus Heyne
German Masterworks
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Audioboffin

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Re: How to keep a condenser capsule clean and dry
« Reply #9 on: August 22, 2004, 11:43:30 am »

A long time ago I worked in a studio with wall mounted lights. We used to leave all the condensor mics on stands positioned a few inches above the lights. It seemed to keep them warm and dry. Does anyone have any thoughts about this method ? At another place we used actual socks over the mics...
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digitaledit

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Re: How to keep a condenser capsule clean and dry
« Reply #10 on: September 09, 2004, 04:01:50 pm »

Al
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djwayne

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Re: How to keep a condenser capsule clean and dry
« Reply #11 on: May 13, 2005, 11:40:46 am »

I keep my Superlux CM-H8A mic on the stand all the time, but covered with a soft leather/suede pouch with a drawstring tied around the mic. Keeps it dry and dust/smoke free, and it looks cool too.

My other mics, I keep in a drawer in an old wooden machinist's tool box.


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David Satz

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Quote:

Do the same rules apply to caring for ribbon microphones?
Nick Kramer


Nick, condenser microphones attract dust and dirt because of electrostatic charges in the capsule. Ribbon microphones don't use electrostatic charges, but they do contain strong permanent magnets. Thus a ribbon microphone can sometimes be a bit more dangerous to other objects in its environment--recorded tapes, for example, or toes that it is dropped on--than the environment is to the microphone.

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AB77

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Re: How to keep a condenser capsule clean and dry if it's a ribbon microphone
« Reply #13 on: February 26, 2006, 06:33:55 pm »

Does anyone know a great foam windscreen that last a long time without this problems of shedding?
THANKS,
AB

Foam in this application needs to be of the open cell variety, therefore the material (plastic) choices are limited, as far as I know, to the type that sheds and deteriorates with time.

We are anxiously awaiting a new foam material which does not shed...
Inventors to the rescue! K.H.
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mikey

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Re: How To Keep A Condenser Capsule Clean and Dry
« Reply #14 on: October 19, 2007, 08:30:04 pm »

Hi Klaus
What about some of these other  microphones that have foam inside the mic heads.I've taken a few mics apart(one to many Shocked ) and the foam turned to powder when i touched it.Does that affect the sound when the foam deteriorates like that.
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