when i first turn my car, or just the stereo on, the sub makes a loud kicking noise, and then a few discreet kicking noises that are still audible for a few seconds until the music plays. if i turn my music off, the subwoofer hums to the tone of the engine idle which is very strange. ive checked the grounds, they could be better but theyve been like that through numerous subs and amps ive used throughout the years and the problem just began with my current set up ( 12" type R and a soundstream TRX700d). its so annoying and its driving me crazy. does anyone know what can be doing this???