Is this a phenomenon? If so, is there anything that can SAFELY soften surrounds that have hardened? I went through this whole 10-page thread and came away with no real answers
https://www.diyaudio.com/forums/multi-way/71420-rubber-surrounds-hardening-age.html
https://www.diyaudio.com/forums/multi-way/71420-rubber-surrounds-hardening-age.html