my brother got 2 12 in jl w6 subs and at low level they sound good but when he turns the radio past 15 the subs start to pop and they are hooked up to a jl 500.1 we dont know y because i got the same set up and i can turn mine all the way up and they dont pop and both amps and radios are set up the same what can be wrong with his the only dif between the 2 set ups is mine got a 3f power cap