Help with Pioneer 8600

Press the audio button on the headunit until it comes up with the controls for the lows mids and hi's...For most systems I think it sounds best turning the hi's and mids to about 4 and keeping the low's set at 0. Doing that will take a good share of the bass out of the speakers. If there is still too much and they continue to distort then set the lows in the negatives..whatever sounds best. Sounds like you might need new speakers pretty soon either way though.