Hi,
out of curiosity I've removed the back of one of my 2421A compression drivers yesterday in the afternoon. What should I say? As expected, I've found the foam in the inside being degenerated, right before falling to dust:
You see the imprints of both leads and two imprints that I did with my fingers to see if the foam would come out again immerdiately. It didn't .
Now, what should I do? Ist this foam still available from JBL/Harman? Or will any polyurethane foam of appropriate thickness do? Is it even better to replace it by felt?
Best regards!