tube amps and electrostatics

Ralph, what you say makes a lot of sense. Notably, take a look at some of the Class A speakers profiled on Stereophile's 2013 List of Recommended Components, here:

http://www.stereophile.com/content/2013-recommended-components-loudspeakers

Most if not all the selected speakers (including B&W 800-Ds)seem to have the type of impedance characteristics you referred to above.

Based on discussions with Paradigm, I'm pretty sure my speakers were also voiced to be driven by a high current SS amp. FWIW, I understand that my version of the Signature 8 (v3) was redesigned whereby the woofers are now 3 db more sensitive. As a result, the mid and tweeter drivers were "unpadded" to be driven full bore. So, the current v3 version has a rated sensitivity of 92 db verses the v2 version, which was 89 db.

I gather that 3 db is a considerable increase in sensitivity. As such, based on what you said above, the S8 v3s are an easier load, regardless of whatever type amp is being used.

Nevertheless, I also gather than even though any type of amp should be less stressed driving the S8s, one is still left with the issue of acoustic coloration, the amount of which is dependent, in large part, on the amp's output impedance. Ergo, the caveat that some tube amps might not be a good candidate, particularly those not using any or very little NF. The same point also being relevant to many other speakers as well, which if technically correct, is an important take-a-way point.

Thanks again Ralph.

Ralph thank you for the explanations. It really helps. I cannot find a impedance graph on my speakers. Is it hard to measure? With what Ralph has said I would like to do that. It seems that would help me optimize my system. Just curious. Thanks. I hope I did't hijack the thread.

Impedance can be measured with a potentiometer of about 50 ohms or so, a signal generator and a DVM. It takes some time, as with this technique you have to put points on a graph.

You put the pot in series with the speaker and drive the combo with the generator. The pot is wired as a rheostat, and adjusted until you see the same voltage drop across the resistor as you see across the speaker terminals. You then measure the value of the pot and plot it on the graph for that frequency. Then you move the frequency and repeat. This takes time to do 20-20KHz, but it works well.

However there are computer programs now that can make the job a bit easier.

The impedance of the speaker does not tell you if it is Voltage or Power paradigm- its easier to find that out by asking the manufacturer what sort of amp they use. But this can be handy to sort out if you have a difficult load in the impedance curve- as we all know, some amps might overheat or the like if the impedance is too low. So it is very useful for that sort of thing.

It was using a technique like this that some Sound Lab customers discovered a few years ago what the Sound Lab impedance curve really was (and it was a lot different then Sound Lab had said at the time). Apparently Sound Lab had used a simulation that had a bug in it. This has resulted in Sound Lab making some changes that not only made the speaker a lot easier to drive for any amplifier, but also made for a better sounding speaker.

12-10-13: Bombaywalla: RE: Stereophile review of Green Mountain Speakers driven by OTL:

They may have given the speakers themselves a good review, but not when it's driven by an OTL amp. And it's those impedances/phase that cause it to act like a tone control.

Stereophile: Listening review of the Green Mountain Diamantes, half way down the page.
http://www.stereophile.com/floorloudspeakers/694green/index.html

And then the measurments by JA to back up what SS heard, first paragraph:
http://www.stereophile.com/content/green-mountain-audio-diamante-loudspeaker-measurements

Cheers George

Thanks for this info Georgelofi. The Diamantes were Green Mtn Audio's 1st offering back in 1994. Not a bad start - much better than most other speakers in the market at that time. There has been considerable advance since then & I believe that Roy Johnson has gotten the phase angles down much more so that the newer model speakers are more amplifier agnostic. I think now Roy Johnson is agreeable to the Atma-sphere M60 amplifier driving his speakers.