ok well i built my own boxs for my subs well i thought i would go get a spl test done at the local shop and found out i had tuned my port way to high now i need help figureing out how to tune this down right now im tuned at about 56 hz and im thinkin tuning them down to about 34 or 36 hz. could someone tell me how to get my port down there heres the out side demsions are 13x20x22 my port is 3x13x14. oo i forgot to tell what i was hitting only 139. so could someone help me out.