A steep phase angle can make a speaker difficult to drive.
Low impedance can make a speaker difficult to drive.
Neither phase angle nor impedance are steady over the frequency range of the speaker.
Phase angle and impedance are not tied to each other--they vary independently.
If one wants to get a better snapshot of just how hard (or easy) a speaker will be to drive, it seems to me to make sense to look at the big picture (aka EPDR) rather than a smaller one (the traditional impedance spec).
Low impedance can make a speaker difficult to drive.
Neither phase angle nor impedance are steady over the frequency range of the speaker.
Phase angle and impedance are not tied to each other--they vary independently.
If one wants to get a better snapshot of just how hard (or easy) a speaker will be to drive, it seems to me to make sense to look at the big picture (aka EPDR) rather than a smaller one (the traditional impedance spec).