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R/E/P => Klaus Heyne's Mic Lab => Topic started by: J. Mike Perkins on June 13, 2017, 03:30:34 PM

Title: Can you re-tension a Neumann K870 capsule using the screws in the capsule ring?
Post by: J. Mike Perkins on June 13, 2017, 03:30:34 PM

This may seem like an obvious question, but if some recent production Neumann K870 capsules sound "thin" from an overly tight membrane, why can't you simply loosen the screws in the plastic ring around the capsule and fix the problem? 

I watched the "How It's Made" TV show where they go to the Neumann factory to show a U87 being produced, and it looked like the screws are simply tightened manually as the capsules are assembled. 

Is there more going on than meets the eye?     

Title: Re: Can you re-tension a Neumann K870 capsule using the screws in the capsule ring?
Post by: klaus on June 13, 2017, 09:23:50 PM

In essence you are right in your description of the diaphragm assembly process, and therein lies the problem with "loosening the screws": Unlike other manufacturers, Neumann does not glue the diaphragms to the mounting rings, but simply affixes them with pressure from the 12 mounting screws.

That also means that loosening even one screw immediately wrinkles the diaphragm irreversibly, as there is nothing else holding the 6µ thin skin in place and under tension.