help subwoofer

Hey guys I have problem and I'm confused because I don't know we're to start , new system set up worked fine , I decieded to hook up compasitor and when I turn up volume my bass went out with amp still on. Feels like the sub is half in and half out is the best to describe. Please help guys thabk u

Hey I was looking for some insight on which 12" or 10" woofer to buy, price range 100-140$. Was looking at sundown ev3 but not sure please help