Re: Humbucker coils in phase with each other?
They are "in phase". The coil windings themselves are out of phase, but both coils have opposing magnetic polarities (due to being on opposite ends/poles of the bar magnet). These two phase reversals put the coils back in phase. The reason hum is cancelled in this case, but not the strings, is because hum is not induced be the pickup's own magnetic field, but surrounding magnetic fields interfering with the pickup's magnetic field. So polarity won't effect hum (polarity will only affect the phase of what string vibrations are picked up by the coil), but the phase of the coil wind will affect both the string vibrations and hum.
So the reversed wind of both coils would cancel most string vibrations and hum, but the polarity reversal (which only affects the string vibrations) will return the string vibrations from each coil to the same phase; but the hum remains out of phase - being cancelled out.
If you were to reverse the coil phase again, since both coils would pick up near identical string vibrations/frequencies, almost all of the signal will be lost, but the hum will be turned back "in phase", so you lose the hum-cancelling effect. In series, the sound is noisy, and so thin the signal is almost non-existent. In parallel, it is just as noisy, but even thinner.
I would not recommend make a humbucker out of phase with itself under any circumstances really. Unless you only want hum/noise.
