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Author Topic: Can you re-tension a Neumann K870 capsule using the screws in the capsule ring?  (Read 1934 times)

J. Mike Perkins

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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?     


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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.
Klaus Heyne
German Masterworks®
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