Lost most of my sound volume !!!

Have just re built my pc with a new MB and chip the MB has a built in sound card and was working perfectly on start up ....Then i started to losse the volume from my 2.1 creative speaker system ...thought the speakers were blown when you cranked the volume up it used to blow you away but all of a sudden most of the volume went to the bass box with minimal amount coming through the satellite speakers....so it was off to pc world to buy a new set which are marginally better but still no where near the volume i used to have ...ie at full volume they are equal to about the 3 or four setting before re build.......any ideas gubbed MB