I have a Rockford Fosgate 250a2 amp and 2 JL W3's. About a week ago one of the subs cut off. I did some troubleshooting and the only channel that works is the one with the red rca cable connected. So basiclly the white cable is dead. I know for a fact that both cables are connected to the deck. Could it be that one cable is bad? They are not expensive cables either. Is there a way I can test the cables?