Balancing headphones does not "just remove the common ground" . It feeds the ground wire for each channel (separately of course) with an inverse signal. So the driver gets instead of signal/ground signal/inverse signal. To make that more easy to visualise you could picture it like: the signal voltage pushes the driver, while simultaneously the inverse signal pulls the driver with the same, but inversely directed force.
12/2/12 at 2:22pm