Caring for your Neumann U87 and other LCDs
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June 9, 2010

 Article by David5437 

It has been about 40 years since I got my first lesson on the do's and don'ts of the care and feeding of large diaphragm condenser microphones  from an old timer that worked in a German microphone manufacturing company.


I do not claim to be the world's leading authority on microphones but since those early days I have lost count of how many hundreds of large diaphragm condenser microphones I have repaired.  I have learned  a lot by my own mistakes as well as the mistakes of others.


One very common problem is when a microphone capsule becomes "moisture sensitive" and I receive several microphones in each week for repair due to this very problem.


I am almost hesitant to write this article. I don't want to shoot myself in the foot by giving you this information because a lot of my business is doing this kind of repair. I have a good relationship with other microphone technicians in this country  who I respect.  I don't want to piss them off by sharing this information.


There are some preventive measures you can take to keep your treasured microphones from getting moisture sensitive which I would like to share with you. A microphone capsule retains a small static charge much like a balloon and attracts dust and other particles that are in the air. These particles adhere themselves to the sticky gold sputtered mylar  that the diaphragm is made out of. After a period of time there becomes a sufficient amount of dust and other particles stuck on the diaphragm and around the ring that holds the diaphragm to the back plate. There is a very small gap in between the gold sputtered mylar and the back plate which allows the diaphragm to move with the vibrations of sound .


When one sings or speaks into a large diaphragm condenser microphone the diaphragm gets fogged just like a window does when you breath on it on a cold day.

This is usually not a problem but your breath has a fair amount of sticky sugar content so when you sing into a large diaphragm condenser microphone it leaves behind a very small amount of sticky spittle residue. After a period of time this residue continues to build up.
Water is a conductor and when these particles get wet they can short out the diaphragm to the back plate through the screws that hold the diaphragm ring in place causing the microphone to cut out and on some occasions it will cause the microphone to die all together. 


One way to test your microphone to see if it is moisture sensitive is to purposely fog the diaphragm  like you would a window while it is plugged in and see if it cuts out. 


If you send your Neumann, AKG or other high end microphones back to the manufacturer for repair they will most likely tell you that you need a new capsule costing  in some cases over a thousand dollars. The original capsule may be far superior then the new mass- produced ones. 99% of the time the original capsule can be repaired. 


The best way to prolong the life of your large diaphragm condenser microphone is to always use a nylon type of pop filter when doing vocals. The metal ones do a good job at keeping "P's" from popping and "W's" from woofing but they do not help much with keeping the moisture out.

The best way to keep the dust and other airborne particles from getting into your diaphragm is to always put it in a plastic baggie when it is not in use, but do not seal the bag so it can breath and dry out. 

Treat your microphones like a good friend and they should give you years of great  performance.


David O. Brown


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