I'm not really sure any of the above loudspeakers have a "smooth" impedance curve.
What's more, I'm less an adherent of this mantra than most. Tube amplifiers prefer higher impedances, and most tube friendly loudspeakers have far more wild impedance curves than the conventional wisdom of smooth impedance curve thinking would ever lead a person to believe.
Why? With most loudspeakers (multidriver and parallel crossover network), the requisites (a bevy of crossover correction/compensation circuits) to produce this desired smooth impedance curve do a lot more harm than good in terms of making the loudspeaker more friendly to a tube amplifier. Put it this way, in order to attain this smooth impedance curve, more crossover parts are required, and crossover parts act as speed bumps in terms of a tube amplifier putting power into a loudspeaker. Beyond that, such "correction" circuits rob the music of life, vibrancy, and immediacy, even if the partnering amplifier seems up to the challenge of blowing through those speed bumps.
As an alternative to seeking a smooth impedance curve, look toward loudspeakers that offer as simple a crossover topology as one can find, and several of the above loudspeakers mentioned above fit that paradigm.
What's more, I'm less an adherent of this mantra than most. Tube amplifiers prefer higher impedances, and most tube friendly loudspeakers have far more wild impedance curves than the conventional wisdom of smooth impedance curve thinking would ever lead a person to believe.
Why? With most loudspeakers (multidriver and parallel crossover network), the requisites (a bevy of crossover correction/compensation circuits) to produce this desired smooth impedance curve do a lot more harm than good in terms of making the loudspeaker more friendly to a tube amplifier. Put it this way, in order to attain this smooth impedance curve, more crossover parts are required, and crossover parts act as speed bumps in terms of a tube amplifier putting power into a loudspeaker. Beyond that, such "correction" circuits rob the music of life, vibrancy, and immediacy, even if the partnering amplifier seems up to the challenge of blowing through those speed bumps.
As an alternative to seeking a smooth impedance curve, look toward loudspeakers that offer as simple a crossover topology as one can find, and several of the above loudspeakers mentioned above fit that paradigm.