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Old 17th Mar 2023, 1:53 pm   #8
GrimJosef
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Join Date: Sep 2007
Location: Oxfordshire, UK.
Posts: 4,310
Default Re: Use of MEK to restore idler wheel

Glycerine also softened the rubber surrounds on some vintage KEF B139 drivers I had. Their specified free-air resonance was at 25+/-5Hz and, presumably, when new the surround was compliant enough that they achieved this (one of KEF's datasheets says that the typical production spread was +/-2.4Hz). After 40-50 years the rubber had stiffened enough that the resonances I measured were more like 35-40Hz. Gently rubbing glycerine into the surround couldn't quite get them back to 25Hz, but it did get them comfortably below 30Hz.

Cheers,

GJ
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