Hmm...
now that I hear about it

maybe its a common problem. I too, hear
low audible sounds, using my powered sub and 2 stereo speakers.
Could it be due to the low bitrate ?? I don't think so. Cause, even DVD
movies are low in sound. So, it MUST be because there is not true suround
sound speaker setup, and the two stereo speakers just ain't enough for
the DTS or 5.1 that the DVD player is putting out.
BUT, if I play my encodes or DVD titles through PDVD, I have LOUD sound.
So, this is mysterious indeed
-vhelp