Which high power SET

I think this discussion leaves out an a couple of important factors. The first is the size of the listening room and the second is the listening level preference. The impedance curve is important as well, but to me speaker efficiency is a much lower priority. For a few years now we have been showing our 300B SET at 10 watts with Fritzspeaker Carbon 7s at 6 ohms and 87 dB. Room size was 13 x 18 or so. No problems whatsoever. Couldn't even get the amp to clip. Room overload was the only issue because we could play it loud.

Hi Clio09,
Not sure if you've read the entire thread. Earlier posts have mentioned room
size and listening levels as important variables that must be considered. As
I told you at CES this year, your amplifier was terrific sounding.
Charles,

I run 85dB (if that!) Infinity RSIIb speakers with a homebrew 200WPC, zero NFB, SET amp and it's the best sound I've ever heard. Crystal clear highs, full lush mids, rock solid thunderous bass. Sounds like a fleawatt SET, with twin superchargers!
Unlike some of the reports here, I do not have a problem with bandwidth at any volumes I care to enjoy, including LOUD.

So, anything is possible.

Action Shot

.

If it's topology, it means harbeths with its low sensitivity are generally incompatible with any SET amp, irregardless of it's power output. Given a hypothetical world where both push pull and SET generate the same power output, does push pull drive harbeths better simply because of topology?

Yes!! What is not getting the air time it should in this discussion is the fact that to take advantage of an SET, **you must not push it past about 20% of full power**!

You can go past that amount with a push pull amplifier and not have ill effects.

This is all about your amplifier investment dollar- with a speaker of efficiency that low, your investment dollar in an SET will not be served due to the fact above.

The impedance curve is another issue! It is pretty evident that the Harbeth is expecting that the amplifier used with has some negative feedback to linearize the output of the loudspeaker. Your EL34 amplifier has that feedback. If you put a zero feedback amp on that speaker its likely that the range of that high impedance in the midrange will take on some prominence.

To understand more about this phenomena, see this link:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

I guess Atma's point also has relevance to my situation, as 20% of 200W is still 40W, which should be able to push my speakers to a little more than 100dB, which is pretty loud.

The bonus is that at 40W, the amps are still in Class A1. Above that they begin to move into Class A2, which would mostly be for big dynamic peaks.

In any case, they work superbly with the RSIIb speakers. However, if you were to buy them commercially (if they were available) you'd be paying a LOT of money, as the parts cost alone was over $11K, with about a year of my time spent in planning and building. The 2.3kV voltage on the output tubes might also cause a little consternation in the family unit...

So I guess the moral of the story is...you can power a low efficiency speaker with an SET very effectively, but it's better if it's a monster-powered SET so you don't operate anywhere near full power for most music, and you'd better be prepared to spend a lot of money doing it.

Would you agree with that, Atmasphere?