"I'm not sure how 180 degrees of phase differs from polarity."
"Dumb question, but what's the difference? Don't they both insert a time delay?"
Polarity is a simple inversion of the electrical signal across all frequencies and is either 0deg or 180deg. All of the signals are inverted in phase with this.
Phase, however, is frequency sensitive in that delaying a signal by a finite time will change differently the phase of each frequency, measured in degrees. For example, delaying a signal such that a particular frequency F is shifted 90deg with respect to the original signal will shift by 180deg the signal at 2F and by 45deg the signal at 0.5F.
Kal