Phase angle has nothing to do with whether the speaker is Voltage or Power Paradigm.
I am always amused by the idea that 'this speaker is hard to drive so get a transistor amp that can double down.' The speaker got the reputation of being 'hard to drive' for a reason; you can count on the fact that a hard to drive speaker will never sound right with any amp, as the amp has to work hard to drive it (equals more distortion, which contributes to harshness).
The simple answer to the OP is look at the designer's intention. For example Coincident Technology uses tube amps for reference- Power Paradigm technology.
Planar speakers of all types tend to be Power Paradigm also. I know these weren't to be in the conversation per the OP, but there it is. Planars don't have an impedance curve based on box resonance, and it is resonance that drives the impetus for the Voltage Paradigm.
An example is a box resonance due to a woofer in the box. When an amplifier that is a voltage source encounters the box resonance (impedance peak) it throttles back its power. This gets flat frequency response in theory.
But just because you have box resonance does not mean the speaker is on the Voltage Paradigm. An example of Power Paradigm box speakers was already mentioned, another is Audiokinesis, where Duke has built speakers that take advantage of the amplifier's power response in a way that allows the speaker an extra 1/2 octave of response in the bottom octave, without coloration. There are many other examples.
I am always amused by the idea that 'this speaker is hard to drive so get a transistor amp that can double down.' The speaker got the reputation of being 'hard to drive' for a reason; you can count on the fact that a hard to drive speaker will never sound right with any amp, as the amp has to work hard to drive it (equals more distortion, which contributes to harshness).
The simple answer to the OP is look at the designer's intention. For example Coincident Technology uses tube amps for reference- Power Paradigm technology.
Planar speakers of all types tend to be Power Paradigm also. I know these weren't to be in the conversation per the OP, but there it is. Planars don't have an impedance curve based on box resonance, and it is resonance that drives the impetus for the Voltage Paradigm.
An example is a box resonance due to a woofer in the box. When an amplifier that is a voltage source encounters the box resonance (impedance peak) it throttles back its power. This gets flat frequency response in theory.
But just because you have box resonance does not mean the speaker is on the Voltage Paradigm. An example of Power Paradigm box speakers was already mentioned, another is Audiokinesis, where Duke has built speakers that take advantage of the amplifier's power response in a way that allows the speaker an extra 1/2 octave of response in the bottom octave, without coloration. There are many other examples.