I have replaced my factory rear deck speakers and also connected a line output converter to run an amp and sub. Since doing so I have a crackle when on AM stations that was not there previously. If the car is sitting still it's fine. As soon as I get moving hitting bumps and suck it crackles. What's the deal? Used the stock wiring from the head unit and spliced new speaker wire into it for the converter. Is the box on the rear deck the antenna? Could I have knocked something loose back there? It's the 6 speaker Setup with 8.4 and nav. Thanks.