z5500 sub blown?

[brfitzp1337]

I've had my z5500s for about 5 months now, and about 3 weeks ago the sub started sounding reallly wierd like it rattles when ever bass goes through it. i checked the fuse and it looks perfectly fine and in pristine condition. Besides all the speakers still work. Is the sub blown? Do you think the 2 year warranty would cover this? if not, is there anyway i could get a replacement.