Car Stereos: no bass comin out of my subwoofers, kenwood amp, line output converter

Question
i have an 01 expedition with a factory mach sound system with a factory amp i'm trying to install two 12inch kenwoood subwoofers and a kenwood amp i did it with a line output converter connected to the rear speakers theres sound but no bass coming out what went wrong?

Answer
Cory,  The first thing that comes to mind is the subs are wired out of phase.  Switch the positive and negative wires of one of the subs, then try it.  If that doesn't fix the problem, there may be some settings on the amp that are set wrong.  Just move all adjustments so any filters or crossovers are bypassed and the gain is turned up.  Hope this helps, Scott