Power output of tube amps compared to solid states

Atmasphere, I suspect that some like; Jim Strickand of Acoustat, Roger Sanders of Sanders Sound Systems (formerly Innersound), Roger West of Sound Lab, Gayle Sanders of Martin Logan, Nelson Pass of First Watt, and Dave Wilson of Wilson Audio might disagree with your proclamation re: the suitability of ss with the types of speakers you've mentioned.
Some would argue that it's actually the additional coloration of tubes that make them appealing.
I would argue that there is greater chance of flushing money down the loo by prioritizing speaker choice to accommodate amplification rather than choosing a speaker which fits in ones budget, works in ones room, and which offer the least objectionable coloration's for the individual purchasing them.

Unsound, if they disagree, its only because they have not been studying what happens that is different between tubes and transistors with respect to how they drive a load. Roger Sanders and I already went around on this one, and if you ask Roger West, he'll tell you that a lot of his customers use our amps... and Nelson Pass has different nomenclature as he uses Voltage Paradigm terms and I don't, but he and I are on the same page here. Just look at his articles about 'current source' amplifiers.

You might also look at a great article written by the chief engineer of EV http://paulspeltz.com/tomcik/index.html

What you get from this article is that there are no known examples of speakers needing over 20:1 damping factors, but that there are speakers that need damping factors of 0.1:1. IOW, the Voltage Paradigm does not work for all drivers.

Sorry for the OT- this really deserves a different thread.

Atmasphere, I do believe your argument has merit. It's just interesting that a couple of those ESL designers also designed ss amps to be used with them. Nelson Pass used ESL's amongst others when developing the Threshold amps. J. Gordon Holt, founder of Stereophile used both tubes and ss with his ESL's. Many of the others used both tubes and ss when demonstrating their speakers at big shows. I would imagine they would want to demonstrate them at their best, and at the very least, not at their worst. I'm sure many who can afford them, use your fine amps where appropriate.
The damping factor issue is a whole new ball of wax, and yes, your probably right, better for a different thread.

Unsound, you are right, a lot of ESL designers do work with solid state. I am of the opinion that they have a particular challenge- break out of the niche that they are in by coming up with an ESL that actually works with transistors...

The problem is two-fold. First, the impedance decreases as frequency increases, meaning that a transistor amp will make more power, causing brightness. Bass is an issue, as there can be some pronounced impedance peaks in the impedance curve. This prevents a transistor amp from making power. This is why a 200 watt tube amp can keep up with a 600 watt transistor amp on a set of Sound Labs, as the 600 watt amp may only be able to make 75 watts in the bass, where the tube amp can be capable of nearly full power.

The second is of course that the impedance curve has nothing to do with driver or box resonance, something that is fundamental to the operation of the Voltage Paradigm. In fact ESLs prefer to see flat power response out of the amp rather than flat voltage response.

To limit these issues a lot of ESL guys keep the speaker impedance very low- 4 ohms in the bass and 0.5 ohms at 20KHz is common. You still have the 8:1 change in impedance, but many transistor amps cannot make much in the way of additional power into 0.5 ohms and at that impedance, the speaker cable itself is a huge limiting factor. Its a band-aid approach, and when you see this its an ESL manufacturer that wants to cash in on the extra market share that they see in transistors.

You may have noticed that this is an entirely different example of how a tube amp with less power can be more powerful than a transistor amp; whenever you are dealing with high impedances this can be the case. Sound Labs have a peak of over 40 ohms in the bass. The 600-watt transistor amp above driving that peak might only make 75-100 watts.

Atmasphere wrote: "What tubes bring to the table is the ability to build a low-distortion amplifier without loop feedback. With no loop feedback, time-domain distortions are 100% eliminated. With feedback, time-domain distortions become the name of the game."

My understanding is that the reason time-domain distortions are of audible significance has to do with the human auditory system. The ear has a characterstic called "masking" by which it ignores a low-level signal that is near (in frequency) to a high-level signal. Audio data compression algorithms (such as MP-3) take advantage of this and simply omit signals that would likely be "masked".

Masking works great in the frequency domain, but guess what - it fails miserably in the time domain! Unless the loud and soft signal happen at exactly the same time, the soft signal is not masked. Distortions that arrive slightly later in time, even if they are much lower in amplitidue, are far more audible than the same distortion which arrives simultaneously with a masking signal.

Duke