Don't know if this would help or not, but...

take a look at the sound control of the computer. Is there a TONE control? If yes...turn the BASS way down, see if that help. Personally I don't think there's anything wrong with Netflix and Hulu...nor youtube, that's just the way it is. By the way, the 3.5mm audio jack is what kind of output, stereo or surround? Also...are you watching tv and dvdplayer via the computer?