I have a 12" XXX in a 1cu ft box with 1000W rms from a kicker 1200.1 and when I have all bass boosts down all the way -18 in all and I turn the volume all the way up I get a slap at full excursion. I checked for air leaks and didnt find any. The XXX should take more but I dont know whats wrong. Any help will help.