Well I have a 2012 Honda Civic. I have one SPL 12" sub in a bandpass box powered by a rockford p300-1 amplifier. I have the factory radio so I used a PAC SOEM-T line out converter. I believe I installed it correctly because it all works. My only problem is that when I turn my car off the subwoofer keeps at a constant boom until I turn the car back on. What could be causing this? I'm new at using a line out converter so any advice to what the problem is would be very helpful.