First Watt: current vs voltage

A current source amplifier has a very high output impedance- usually multiples of the speaker impedance.

A voltage source amplifier has a low output impedance, usually a small fraction of the speaker impedance.

Either one can sound good, but as far as what speakers work with them has to do with the speaker manufacturer's intention- whether the speaker is designed to work with voltage source amplifiers, power source amplifiers (tubes) or current source amplifiers (usually the latter employ some sort of current feedback which increases the output impedance).

The issue is two-fold: first, the crossover frequencies may not work right as the way these amplifiers behave is very different (an example here is using horns with voltage source amplifiers often results on horns that honk, due to the crossover not working correctly with the voltage source amplifier), and then if there is a port or other means of dealing with the box resonance, that may not work right for the same reason.

This is why equipment matching between amps and speakers is an on-going conversation in high end audio. Now if the speaker is OK with SET amplifiers, it stands a good chance of also working with a current source amplifier. So in this case its worth an audition- see what you think!

I have always seen voltage source attached to amplifiers that are capable of a high output in amps and can increasing their output into lower impedence loads. IE Krell is a voltage source amp, a Quad 405 isn't.At least this is the usage in England that I have seen in reading HF mags the last 40 years.

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Stan, sort of.

For a given input voltage an ideal voltage source will maintain a constant output voltage no matter what the load i.e. no matter how low the load impedance goes and no matter how much current the load draws. This requires the amp to have extremely low output impedance, ideally zero. Monstrous power amps like Krells are closer to these ideals than the Quad but they are both considered voltage sources.

Current sources are an entirely different beast.

For a given input voltage an ideal current source will maintain a constant output current no matter what the load. This requires the amp to have extremely high output impedance, ideally infinite. The First Watts are not that high with an output impedance around 80 ohms but that is 10 times most loads so they act more like current sources.

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Good discussion.
I've seen a particular modder design series crossovers for Magnepan panels.
Makes me wonder if this would be the way to go with higher powered tube gear, like the ARC stuff, which I sometimes seen mentioned as playing well with Maggies.
The old / original crossover for the MMG (maybe the SMG) was a series crossover.

What about just putting a couple ohms in series with my amps outputs? Would that work? Carver did it a couple years ago......

What Carver did was supposed to make the amp sound like a current source but it didn't actually make it one if I remember correctly. I don't believe adding resistance will do anything except possibly change your crossover and burn up more power driving the resistors.