weird sub behavior

k lets see if i can explain this
first my system
kenwood in dash, mtx amp(the big one) with adjustable fade(i think thats what its called, its a switch that can make bass louder or softer), and 2 12" infinity perfect kappa 12.1, in a q logic bandpass box, and a lightning auio strike cap 1.0 farad

well when i have the bass about 1/2 on fader, and stereo at 18 my bass is fine nice and loud, but if i bump it up it sounds like the bass is skipping or only giving partial beats like just beginning and drowning out rest.
I have checked all my connections and they are all good, lights arent dimming, so i am stumped and i am awesome with electronics but still dont know what is up

Please help me.