Sound on Ps3 Video 9

[Drillakilla]

Hi guys, just need some help, and can't work this out

So far I have converted many mkv movies ( 720p x264 with ac3 sound) into 720p avc files, now the sound is what I have the problem with, I don't seem to get enough bass, is there any setting i can tweak to fix this?

Any movies I have converted that have originally had DTs sound have come out excellent with a rich creamy bass