sub doesn't work
 

I have 95 sc300.. I think my subs are dead. But my friend told me that there a separate amp for the sub. is that rite? He said it next to the panel in the rear passenger? Or does the SC only have 1 amp to share everything. I dont know if my amp is dead or sub, but I think my speaker work perfectly fine. I sat in my friend SC and known his sub works, and i can really tell a big difference.