iPod subwoofer woes

Hey there, Well I just setup my iPod with my Pioneer 7500MP deck by purchasing a cable that was advertised as "similar to the CD-RB10" that used the P-bus connection on the back of the deck so that I could have a direct connection to the stereo. The only problem now is that my sub barely responds to the music. It will only hit every once in a while. I've tried tweaking the settings on the amp but that just amplifies the bass hits that were already few and far between. I was wondering if anyone knew what was happening, because right now I don't see the point of carrying along my iPod when cds sound a lot better. Thanks.

what kind of compression and what bitrate are the files on your ipod encoded at? often the compression means the lows and highs get cut, try using a file at a high bitrate or use apple lossless and see if you still have the problem