Got major feedback noise out of speakers especially at low volume. When turned up it drowns out the noise. Got 2-800.4 Kickers with 1200.1 Mono. I've got good grounds, the deck is JBL marine. Does filter really work. The noise is bad?

check your RCA's

are you splitting the rca's or have a crossover in the line ?

As said above disconnect the RCA's and see if the noise changes. The noise can come in through the power feed wires also, like if they are run near a coil, tach lead, alternator etc.

That is funny you said RCA's, the speakers on the right side under dash stopped working. I pulled RCA's and pluged back in and they started working. The RCA's are split so I think they might be bad. Should I change them all to something high end?