My subs sound good but when they start to BUMP they rattle and my friend says check the levels, I got 4 knobs First knob is MAX LEVEL, the next knob is bass boost, third knob is low level and last knob is high level, i know i dont need that one, but i have most of them turned all the way to their fullest and my subs sound like crap, now i know thats the reason but i can't find the right combo for them to sound decent either, thats for the help
max level is probably your gain. set that NO HIGHER than half way up. Set low level to about 80Hz. I don't know the LPF range for your amp so I can't guess at the position for that. set bass boost to "flat" or minimum. this will only cause clipping.