Your new head unit, like most, mutes the output when you are changing inputs or tracks. Each of your factory Bose speakers have a built in amplifier with a circuit that turns them on when they 'hear' a sound signal on the speaker input leads, and off when they 'hear' none. So - for the split second that your head unit mutes its outputs, your speaker amps turn off, then back on again with the new signal. Because the impedance is not matched between your head unit and the speakers (which are non standard), you get the pop. I've been there and done a ton of research on it.
22:04:36 03/16/10
