@inscrutable wrote:
"if the amplifier has a very large - let’s say infinite - current capability, so can maintain voltage to be applied as the speakers impedance changes with signal frequency changes …?"
A constant-voltage amplifier will put out reduced wattage into a higher impedance. That's just the way that type of amplifier behaves.
However a constant-power amplifier will put out essentially the same wattage into the speaker's impedance even as it changes, at least within a realistic range of change.
Most tube amplifiers have a constant-power characteristic, and therefore the system's dynamic contrast would be less sensitive to heat-induced changes in the drivers' impedances.
Duke