Headphones

while listening music through a head phone many may have noticed that
sometimes a particular sound may appear to come from the centre of the
head and sometimes from both of your ears simultaneously ...

Howz that ??
I suppose that if the electric signal comes to both of the speakers in
the head phone in phase, the music will appear to come from the centre
of your head.and if there is a phase shift (multiples of
360degrees)between the signals then the sound will appear to come from
the ears simultaneously..

Is that true ??