tube amps and electrostatics

George, I did a web search for an article that explains EPDR. I found an article authored by Keith Howard printed in Stereophile (July 2007), here:

http://www.stereophile.com/reference/707heavy/index.html

Mr. Howard explains in simple to understand concepts what I have been seeking for some time. Namely an article that folds impedance and phase angle stats together in a way that provides useful information about speaker and amp compatibility.

If Messrs. Howard or Atkinson, or you too George, get around to starting up the SPCA (Society for the Prevention of Cruelty to Amplifiers), send me an application form.

And as usual, we audio dummies are at the mercy of an industry that is not as transparent as it should be. To quote Mr. Howard, "[EPDR] import seems not to have suffused audiophile consciousness. Speaker reviews don't address this issue, and neither do many speaker manufacturers, who are apparently happy to throw the output-device dissipation problem over the fence for amplifier designers to deal with."

Speaking just for myself, I'm embarrassed to call myself an audiophile for not having better quantifiably grasped these concepts a long time ago. What I wound up slapping together is hard to call a system. More the result of sheer dumb luck.

Good night Gracie,

Bruce

Bifwynne, speakers get a reputation for being 'hard to drive' for a reason. What you might want to think about is the impact on the amp. It does not matter tube or transistor, if the amp is driving a hard to drive load the result will be more distortion from the amp.

For this reason you are usually better off, if sound quality is your goal, to get a speaker with higher impedance (as they are often easier to drive), regardless of the type of amp. Now if **sound pressure** is your goal, then a lower impedance speaker can help if you have a transistor amp.

But usually in high end audio we are more concerned with finesse. So this is something to consider! FWIW, most loudspeaker designers have not sorted out this simple fact that I have posted above. So you will continue to see lower impedances regardless of the speaker technology.

IOW if you were simply able to raise the impedance of a speaker without changing anything else, it would sound better as the amp driving it will sound smoother and more detailed due to a reduction of distortion. ESLs are no different and this is why the ESLs with higher impedance curves also have the most loyal following (they sound better). That is why the *ancient* Quad ESL57 is still around and still has loyal fans. Its easy to drive.

Ralph, maybe my aim is way off. Instead of picking on amp manufacturers, maybe it's the speaker manufacturers who should be taken out to the woodshed.

But first, let me be generous by at least asking if it's the nature of the beast and the laws of physics that is the reason conventional cone speakers have flaky impedance and phase angle curves? Stated differently, is it possible to design a cone speaker that performs well *AND* has benign impedance and phase angle curves? And is also reasonably sensitive??

I imagine the "SET-heads" must use such speakers or else SET amps just wouldn't do the job.

Bruce

Is it only flaky if the amp can't handle it? Perhaps the speakers performance benefits from it?

Stated differently, is it possible to design a cone speaker that performs well *AND* has benign impedance and phase angle curves? And is also reasonably sensitive??

yes! Roy Johnson of Green Mountain Audio has been doing this for a long time now. He's well known but not an audiophile household name like, say, B&W. But his speakers are all cone-driver types & they are often 6 Ohms & they have very little phase shift in the 200Hz-8KHz band (we're talking 10 degrees or less) & outside this band the phase shift is more but nowhere near the speakers that are members of the Society for the Cruetly to Amplifiers. Green Mountain Audio speakers are easy to drive - a 30W/ch RM10 from Roger Modjeski will drive many of his stand-mount speakers to sufficiently high SPL. The Green Mountain Audio speakers are in the 90dB sensitivity range.
here is a link to his Rio speaker design notes:
http://greenmountainaudio.com/storage/speakers/rio/Rio-Design-Concept.pdf
i realize that no phase plot is given but one can assume from the flatness of the impedance curve that the phase is also relatively flat (note that wild impedance curves & wild phase curves are related - when you see one, you see the other. Do an empirical check to convince yourself).
here's a review of the Callisto speakers on 6moons:
http://www.6moons.com/audioreviews/gma2/callisto.html

The Green Mountain Audio speakers always sound like music on all your genres of music. I recently heard them again at RMAF2013 & they once again delighted. Stereophile gave Green Mountain Audio some very good press:
http://www.stereophile.com/content/marigo-whirls-green-mountain
Roy Johnson on the left (& Marigo Audio Labs owner on Ron Hedrick on the right).

For me speakers from the company are really the best & I can't seem to listen to any other type of speaker as they seem "broken" to me (my understanding is that the Apogee Scintilla also has a 1st order x-over).
No financial or otherwise implied relationship with Green Mountain Audio. Just a happy former owner.
Thanks.