My friend had this happen with his MTX 5500. What it was, was that the sub was pulled back when he stopped the song and right when he put something new in, it bumped (since it had to release). Maybe this is what's happening with your subs also.
Well, maybe your very accurate at changing songs right when your subwoofer is ready to bump? I don't know, other than that, I don't know what could be going on but, im sure someone will read this thread with all their car audio know how and know exactly what's wrong...
A sub shouldn't "have to release" as you put it. I've never seen a sub stick when you change the song or whatever. Although, I have seen a sub get stuck all the way out, like the vioce coil jumped out of the magnet and got stuck.
its not my subs or amp i dont think because i had a sony 1200wat amp with 2 sony 10inch and it did it and i baought new 12s and did the same thing and now i have a new amp and subs and new wiring and rcas, it used to be really bad it would thump really hard with the volume down all the way and it would do it while playing music then i changed to a old crappy deck and it didnt do it, then i put my new deck in again and changed the ground on my amp and it stoped thumping at 0 volume but it still does it when my amp powers up and when i change the song? i dunno
Lol, Yes, you have a grounding issue. Don't use the factory ground/power for you Head Unit. Check all your grounds. If that fails, try a common ground, wire all the electronics that are related to your stereo to one point or in close proximity to each other so they are seeing the same resistance. Your grounding could also be insufficient.