ULS-15 Subwoofer speaker dead?

[rmcfee]

I have a ULS-15 from 8 years ago and it has worked great. However it has developed a problem:
a friend was doing a room EQ test and it involved a signal that started REALLY low and progressed up through the high frequencies.
At the very low frequencies the sub would make a weird high pitched squeaking sound like metal rubbing or something.
When I investigated later I noticed that if I pushed in on the woofer I could feel a rubbing sensations.
Then when I played vinyl a high pitched sound would occur and it only stopped when I unplugged the sub!
I tightened the driver screws a bit but it didn't help. It is a MASSIVE 15" speaker to say the least.
I tried a different cable and it still made the sound.
Is the driver simply blown? Thanks.

[ATL]

I had the same problem a few years back. High-pitched chirping sound. The deeper the source material, the louder the chirp.
Luckily I had 2 subs (ULS-15), so was able to troubleshoot them by swapping amps between the two, and the problem followed the amp. So I knew it was the amp, not driver, that was at fault.
Sent the bad amp back to Hsu for repair, and that fixed the problem.

[rmcfee]

Was the repair costly?
I hooked up the HSU driver to my amp and played some tunes and there was no chirping.
So I guess that means it's the amp. Thanks.