+1
DO NOT ATTEMPT TO FIX THESE WOOFERS!!! They are essentially unobtainium and if you do any work on them, the likelihood of a positive outcome is low.
I'm pretty sure this is purely a cosmetic issue. JBL used a foamed rubber that is called EPDM. You should find out if there are cleaners for this exact type of rubber that will not damage the rubber or shorten its life.
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