Well out of no where my subs have started to make random noise when I first start my car. I don't hear it out of my speakers or anything just my subs. Its not really any kind of song or what not, its just random low level noise coming from them and then all of a sudden just stops. So far I can only tell its happening when I start the car. Turning up the radio or turning it all the way down doesn't change it. What could it be?