Jay wrote on Sep 30, 2011, 22:09:
Yeah, that's a big problem with Realtek chips. They're perfectly capable of outputting bass, but apparently their programmers don't know how to do LFE crossover at the driver level. If you use a media player or play games using an audio API that does it manually (Dirt2 does, I think), you'll hear perfect bass again. Of course, most games don't, because it's the kind of thing that soundcard is responsible for doing.

External soundcard might be the only option for you.