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[DRONE7]

Oil of wintergreen?

I might try that on my vintage KEF Q60's although the surrounds are still like new and I'm not so sure about the minty smell from that oil ;-)

If it ain't broke...  

Yes, there is very little WAF in a living room reeking of sports therapy....and it takes several weeks to become bearable .... ask me how I know..  

Here is a good, well thought out and applied test of several treatments to 'soften' old hard rubber.
https://www.youtube.com/watch?v=EnGsllKvheQ