Onkyo Precise Acoustics

I have some nice speakers made with remnants from Parts Express excess. 8
inch woofers have a rubbery type surround. Just in the last two years the
surrounds started breaking what looks like tearing apart. I have redone the
two sets with rubber replacements think they are working well. Just
wondered if anyone knew what type of rubber they used. I guess they were
made in late 80s by Onkyo, so that would be about 30 years old. The driver
was on the front cover of a Speaker Builder Magazine with Keith Johnson.

Greg