tube amps and electrostatics

^^ Yup! We shown with Roy's speakers at audio shows in the past. Never had a problem with them.

Not to worry, enjoy the speakers; there are amplifiers up to the task, and with more to spare.

I need to point out to you Bombaywalla that this Green Mountain speaker is far from being a hard load, if fact it's quite easy.
As it's a 6ohm average with a not so bad phase angle of -30degrees.
The worst load frequency for an amp happens where they cross at 100hz where the impedance is 6.5ohms with -25degrees phase angle.
So this speaker can be regarded as quite an easy one for amps to drive.

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.

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

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.

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.

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.

****Whoops, mean't to say macrodynamics there actually. Sorry. ES speakers I have heard tend to have microdynamics in spades.****

Phew!!! Had me worried there for about a second or two.

"They were a reference standard for me as I heard them in every area except microdynamics. "

Whoops, mean't to say macrodynamics there actually. Sorry. ES speakers I have heard tend to have microdynamics in spades.

"The requirement of the speaker is such that almost any amplifier driving it will have to have a fair amount of feedback to do so. This will cause the amp to be un-naturally bright. IMO this makes the speaker a poor choice as you will not be able to find an amplifier that will actually cause the combination to sound like real music."

B&Ws like those often tend to sound bright to me as well, but not always.

I'd compare those to my OHM Walsh speakers, which has impedance drop just below 3 ohm in teh mid bass region based on measures I have seen, but seldom ever sound naturally bright. There a single Walsh style driver does most of teh work up to 7khz or so. There is no driver efficiency mismatch issues to deal with in teh case of the OHM CLS driver. I suspect that might be part of the reason.

MY Bel Canto Class D amps use feedback as well. Brightness and/or fatigue is a non -issue.

I auditioned modern Quad ESLs prior to trying the OHMs. They were a reference standard for me as I heard them in every area except microdynamics. The OHM sound resembles that ES sound with the right amp + the macrodynamics one associated with a traditional dynamic driver.

The B&W 802D is, FWIW, an excellent example of Voltage Paradigm technology.

The woofers are each 8 ohms, but also 3db less efficient than the 8 ohm mid range and tweeter. They are in parallel, which requires the amplifier to double its power into the woofer load. This brings their output up by 3db, causing them to match with the rest of the speaker.

Yet the spec on the speaker says they are 'nominally 8 ohms'!

The requirement of the speaker is such that almost any amplifier driving it will have to have a fair amount of feedback to do so. This will cause the amp to be un-naturally bright. IMO this makes the speaker a poor choice as you will not be able to find an amplifier that will actually cause the combination to sound like real music.

This is not true of ESLs.

These links will get you there better

B&W802D EPDR load
http://www.stereo.net.au/forums/uploads/monthly_12_2013/post-106386-0-82896500-1386705003.jpg

B&W802D non EPDR load
http://www.stereo.net.au/forums/uploads/monthly_12_2013/post-106386-0-58273700-1386705013.jpg

Cheers George

"12-09-13: Bifwynne
George, I did a web search for an article that explains EPDR."

Good to see someone is starting to grasp it, I posted (link) 2 graphs of the B&W802D one that shows the impedance and phase angle as separate measurement lines, and the other graph in red that shows them combined to give the actual EPDR load the amp is seeing.
Note the big difference at 60hz and at 700-800hz where the load the amp sees, drops to almost 1 ohm (EPDR) from 3ohms (non EPDR)
http://www.stereo.net.au/forums/index.php?/topic/59228-class-d-amplification-explanation/#entry1010538
And look at the Wilson Alexia comment as well.

Cheers George

+1 Mapman

"ARC Ref 150 has muscle power and a large reserve power supply, plus my speakers are reasonably sensitive (92 db)"

That's a pretty solid combo on paper that should be capable of delivering the goods with the right tweaks.

No system is inherently good. Its what you do with it (the "smart" tweaks) that matter.

Bifwynne, another speaker you might look at is Audiokinesis. His speakers are not only more efficient, they are also very easy loads (some of them are 16 ohms) without crazy phase angles, yet also quite musical and good bass extension.

I think you are correct that speaker manufacturers ought to be taken to task. Back in the old days when tubes were the only game in town, speakers were a lot more efficient and higher impedance. When the less expensive power of solid state came along, we saw both impedance and efficiency go down.

When transistors came along, amp manufactures realized they could build an amp with same power as a tube amp, but it might only cost 1/10th as much, yet they could still charge 90% of the tube amp retail cost. A similar thing was going on with speakers- its costs about 1/10th as much to build a lower efficiency driver (as opposed to a high efficiency driver). To get back some of the perceived loss of efficiency, the impedances headed south. IOW, its all about the dollars.

IMO its telling that you can have two speakers, one 10X more efficient, and the more efficient one can have the same bandwidth and be just as revealing, IOW not giving up anything for being more efficient.

I can't think of a good reason for a high end audio loudspeaker to be less than 8 ohms. I've mentioned this plenty of times before- the lower the impedance, the higher the distortion, making any amplifier harsher and less detailed due to the types of distortion and our human hearing/perceptual rules. IOW if you want to make a speaker that seems smoother and more revealing, all you have to do is increase its impedance (all other things being equal- same box characteristics, same crossover points). It will not be that the speaker itself is all that different, but the sound of the amp driving it will be!

Thanks for the heads-up George. I'll do some checking. At this point, more from dumb luck, I may have a combo that works ok because my ARC Ref 150 has muscle power and a large reserve power supply, plus my speakers are reasonably sensitive (92 db). Otherwise, I would have been another hapless victim. I'll be smarter next time when I upgrade speakers. That's for sure.

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.

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

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

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.

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

Thanks George. Is it a gross simplification to view EPDR as a "refined" version of impedance which will provide a clue about the load an amp is facing when driving a speaker at various frequencies?? For example, the EPDR of the Wilson Alexis at one point was .9 ohms, which I assume is not particularly amp friendly.

Also, as a practical matter, most impedance and phase angle curves vary significantly as a function of frequency. So what's the deal if a speaker's EPDR in the bass region is .9 ohms (ala the Alexis), but the bandwidth saddle is only say, ... 50 Hz?

Thanks again George.

Bruce

Bifwynne
EPDR is not simple to work out you need Matlabs program that cost + the equipment to measure both parameters, unless you know the resistance and phase (which Stereophile do give) then all you need is the program.

Here is a link to the EPDR discussions on Stereophile with John Atkinson editor who's not using it yet and Keith Howard who does uses it from HiFi News & Record Review.

http://www.stereophile.com/content/epdr-wheres-formula-footnotes-1

Cheers George

+1 Lacee

My observations over the years has led me to believe that you either are a stat/planar lover or a cone lover.

Sometimes people shift sides over the years,for whatever reasons, but I have known more folks to stay in the planar/stat side of the speaker family once they've been exposed to a good set of planars/stats with proper amps SS or tube.

One of my friends bought back his old MonitorX stats after a decade or more of bouncing from one cone to the next.

Stats/planars have a certain sound and room interface that cones do not and cones can interact with a room in ways that planars cannot.

Our ears are the final arbitrator of what appeals to what we settle for,and neither speaker type is the best.
Nothing in audio is the best, there will always be something that was better or will be better or that can be made to be better than what we now consider the best.

So for me, what type of amp is best for an electrostat is something that only my ears can tell me.
It could be either, depends on the speaker and the rest of the gear, and the type of sound that I have groomed my ears to accept as pleasurable.
But my ears aren't the same as everyonelse, and what I consider good may sound like crap to someonelse.
We develope, over time and exposure to great sounding systems(seek them out and educate your ears)a sort of appetite for certain things.
Like going to restaurant.Somethings on the menu are appealing while other things are not.

I am not a sea food lover, but I know a lot of my friends are.

Some folks like cone speakers, some like stats or planars.

There also seems to be cookbook like recipes from audio gourmets who preach that cones like powerfull solid state amps that control the woofers with a high damping factor.
While some audiophiles drive 15 inch woofers with 2 watt SET and are quite happy with the results.

Lots of options on the menu, try them all until you find the ones that fit where you are NOW at this stage of your audio journey.

I've been thru several stages.
Each one was a place I could have stopped at, yet each was different from the one before and after it.

Did this make me a tortured lost soul, we so often read about?
You know the fellow who has to get off the merry go round, the fellow who has to downsize, the fellow who has found that this hobby is nothing but a sham and full of shills and snake oil, the fellow who believes that nothing good has been made in the last 40 years and that somewhere something went wrong and we lost our way, and nothing will get his mojo workin.

Nope.
That's not me.

I've found that there's so much good stuff out there, new and old, that putting together a system today that sounds great to my ears, is easier than it's ever been.
In spite of all the hand wringing we read about,you can mismatch an amp with a pair of speakers and be perfectly happy with the results.
I know a lot of folks who have done that.
And I have friends who are tortured souls,
They like the sound of that tube amp on their stats, but because someone says it's not politically correct, they have a change of heart,and set about looking for a solid state amp to correct the error of their ways.
But then the torture sets in because they like the sound of tubes,so on and on it goes.

A state of constant flux is a good thing.
Searching for that elusive absolute sound,in whatever way you want to define it, can be a fun thing or a totally frustrating one.

It depends a lot on your frame of mind.
Some folks constantly torture themselves flitting from one thing to the next searching for a nirvana that only exits in their mind or the mind of the audio guru of the day..Made ever so hard to achieve because one never knows what nirvana sounds like.It's always changing.
The reviewers are always finding something new that's the best.
When you accept that nothing is perfect it's just a state of mind, you can start to accept the flaws that all speakers and gear in this hobby have and learn to live with them.

I have learned to live with and accept the flaws in my stats and with the gear that drives them.
The positive things that I like about my sound out-weight the negatives.
I have heard better,but at far greater expense,and with flaws of their own.

So I've learned that nothing is perfect at any price point.
The fun thing for me is to find things that will make what I have sound even better, so I have gotten off the speaker, amp merry go round and stopped swapping components.
I've assembled some decent pieces and they work together.

I've heard some of those mega buck systems, and some are very good,but if money was no object, I couldn't decide on what I would buy.
They all sound great, and different at the same time. So which one is the best? The one to end with? At some point you have to settle for what you have and start to appreciate it flaws and all.

We can split hairs for the rest of this century about what is the best amplification for stats, or if Maggies are better than stats or if Apogees are the best etc.

In the end it doesn't matter,there will always be something better.And someone to tell you so.

So move on to it or tweak what you have to a place that you are happy with.

George, your post just above quotes my use of the phrase "increased emphasis of the upper treble" for the second time in this thread, and both times you've omitted the words which immediately followed that phrase in the same sentence (see the second of my posts dated 12-4-13), which were "in comparison to nearly all tube amps."

That sentence says nothing whatsoever about whether the acoustic response having greater emphasis of the upper treble or the acoustic response having lesser emphasis of the upper treble will be more flat, or will be more musically correct (however that may be defined). As I indicated in the subsequent sentence, those are separate questions.

Numerous opinions relating to those separate questions have been expressed during the course of this thread by highly knowledgeable people, who in some cases drew careful, informed, and informative distinctions among different kinds of ESLs. As I see it further debate on those questions would amount to repetition of what has already been said, and would therefore be pointless.

I had read Mr. Sanders' paper, btw, and without getting into specifics (which would necessitate a very long post) I'll just say that it doesn't change any of my opinions, at least with regard to ESLs other than his own.

Regards,
-- Al

"increased emphasis of the upper treble"

Not right, "emphasis" is the wrong word it will give a flat response through the audible frequency range and cannot boost at these frequencies thus will not be effected.
And yes it will have more presence than an amp that is curtailed in these harder to drive areas because they cannot deliver the constant voltage because of limited current.

Just read and try to understand Roger Sanders WHITE PAPER on the subject.
http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors

Cheers George

Thanks George, I read the article that uses the term EPDR. It appears to be a numerical factor that in some way combines and restates a speaker's impedance and phase angle attributes at a specific frequency as some sort of "impedance prime" equivalent.

Is there a formula that would enable one to make an EPDR calculation? What about cases involving inductive phase angles? How is EPDR computed in such cases? Are they hard on amps (tube or SS) like capacitive phase angles? Lastly, how significant is a low EPDR at a particular frequency when the frequency range where the EPDR is low may only be 10 or 20 Hz wide??

"EPDR (equivalent peak dissipation resistance)." Que'est ce se mon amies??? [What does it mean my friends?]"

It is used by technical measurers like Keith Howard of HiFi news & Record Review, and John Atkinson of Stereophile when they review and then measure speakers. Because just a low impedance measurement does not reveal all that the amplifiers is seeing as a load.

The lowest EPDR (combind resistance and phase angle) of say the Wilson Alexia when measured by Keith Howard of HiFi News was a low impedance of 1.8ohms at 65hz and a lowest phase dip of negative -40degrees also at 65hz. These two measurements combined gave the Alexia a load to the amplifier of .9 of an ohm at 65hz. Big difference to just 1.8ohm resistive load.
You can read all about it here.

http://www.absolutesounds.com/pdf/main/press/WA%20Alexia%20HFN%200313-4web.pdf

Cheers George

Frogman, your post of 12-5 here is one of the best of the kind I have seen on this site - thanks!

Bifwynne, I have to admit that on some level I agree, finding suitable amplifier compatibility for ESL's seems to be a bit daunting. While I've admired some of the qualities in ESL's in the past, certain aspects have kept me apart from them. I've yet to hear the mixing and matching of conventional drivers with them in the effort to negate the often heard deficiencies in bass response and macro dynamics done successfully. Still, they do seem to offer some superiority in other areas. In the past, I have attributed my perception of uneven frequency response in ESL's due to the challenge of properly coupling their somewhat unique dispersion patterns to the rooms they're placed in. Perhaps that was misplaced. Was the uneven frequency response I've experienced due to amplification issues? Though these challenges might be too much for me to overcome, I can still understand why some would be attracted to ESL's, despite these observations. Furthermore, I have still yet to hear the a couple of the most very favorably reviewed brands, so I keep an open mind to their ultimate capabilities.

Thanks Al.... Headphones is where my wife wants me to go. When my wife begs me to lower the gain, and then violates the serene sanctity of my blessed man-cave when she does so, I promise to turn the rig down, but turn it back up even higher when she leaves. LOL :)

Clearly Al, you are much more the gentleman than me because you switch over to headphones so as not to "conflict with [your] wife's activities." AL, ... I'm 19-year old child trapped in a 60-year old body -- just like a rat trapped in a steel cage.

I get the idea that negative phase angles coupled with low impedance attributes in a speaker's bass frequencies makes for a difficult to drive load. But good ole' George dropped a new term on us tech newbies, "EPDR (equivalent peak dissipation resistance)." Que'est ce se mon amies??? [What does it mean my friends?]

All the best guys. And ok, I'll put ESLs back on the speaker possibility list.

Regards,

Bruce

Bruce (Bifwynne), the lengthy response Ralph (Atmasphere) provided above to your last post provides, IMO, a nuanced, balanced, and technically sound perspective on the issue, derived obviously from extensive experience as well as technical expertise.

Here is another idea to consider, though: Supplement your dynamic speakers and the ARC amplifier with a set of Stax electrostatic headphones and a dedicated Stax headphone amplifier. That's what I do, and I really enjoy having the two different perspectives on what a given recording has to offer. As well as the fact that headphones eliminate (and facilitate assessment of) room issues, and allow me to listen at times when listening via speakers would conflict with my wife's activities.

Just a thought. Best,
-- Al

Mapman: "Over sweet treble and midrange bloom"

You forgot to include the word "recessed" you guys are just too much.

Cheers George

This thread has rekindled my interest in es speakers.

Over sweet treble and midrange bloom..... Sounds enticing!

Yes Twb2, unless your prepared do your homework to get the right amp with ELS's, they will be a comprimise at the low impedance + difficult phase angles frequencies, as Roger Sanders ( in his White Paper http://sanderssoundsystems.com/technical-white-papers/172-tubes-vs-transistors ) and I have outlined a few times above, that many tend to be blind to.

Here are two more and there are many more on all brands of ESL's

Martin Colloms from HIFI Critic Report on the Quad ELS-2805:
"Amplifiers with more
than 0.6 ohms output impedance (which most tube amps can be) will cause shifts in tonal
balance, namely recessed over-sweet treble, and some
degree of lower midrange boom and bloom."

And also Keith Howard from HIFI News report on the Quad ESL-2912
" Impedance phase angle at low frequencies
is high enough to lower the EPDR (equivalent peak dissipation resistance)to a minimum ohm of 1.4ohm at 69Hz, but as the ESL- 2912's impedance will be level-dependent at LF the dips to 3ohm modulus at 7.5kHz and to 1.6ohm EPDR at 11.lkHz are more relevant and suggest a moderately difficult amplifier load."

Cheers George

Autoformers in finished boxes showed as costing over a grand. A barebones version would be less i suppose. Es speakers can be pricey, so its all relative i suppose.

Mapman, your original comment was

Autoformers cost more than many speakers themselves. That's a factor to consider in the equation that can't be ignored.

If you're talking about some of the smallest hybrid ESLs on the market, especially purchased used, you may have a point, but that is not 'many' compared to prices of ESLs currently manufactured and certainly not the majority no matter how you slice it.

^^ yes. But then you are dealing with 20 ohms or more in the bass. A 600-watt transistor amp just became a 250-watt amp.

This is why tubes work so well- the higher impedances are not as challenging. In the case of the Sound Labs, this means a 150-watt tube amp can keep up with a 600-watt transistor amp no worries.

Wouldnt two ohm or less impedance at high frequency be much easier for a ss amp in particular to deal with than if it were low? Way less power needed for high frequencybthan low. Or is it more complicated than that?

Es speakers are special and worth any special effort needed. Plus you have some good sidekicks here that can help to get them singing.

Bruce, I would not loose heart!

The issue that makes ESLs hard to sort out is that their impedance curve is related to a capacitor rather than drivers in a box.

But the allure is of course that ESLs are very fast and revealing, and if set up right, not painful for all that extra detail.

I agree that some things about ESLs can be counter-intuitive. For example many magazine articles have been written about how hard they are to drive, difficult load yada yada, but that really isn't the case.

OTLs, as you know, have a reputation about being load sensitive, but oddly have also been the preferred combination with ESLs going back to the 1950s. We have made that even more difficult for ourselves (since we make OTLs) by removing the feedback from our amplifiers, yet still they are able to drive ESLs quite well. So the 'difficult load' thing is really a common myth not supported in the field.

What *can* make an ESL hard to drive is when the manufacturer of the ESL decides he wants the speaker to be more transistor-friendly. MLs are a good example- 4 ohms in the bass, 0.5 ohms at 20KHz. Now there are many who would say that is a difficult load, but there are no crazy phase angles, so with proper matching (a set of ZEROs) such speakers become quite easy to drive with tubes since its more about impedance than anything else.

If you are contemplating going from a box speaker to an ESL, you may have to deal with things like having the speaker further into the room to make it play right. However the energy that comes off the back of the speaker is used by the human ear/brain system to get a better idea of where the sound is coming from; IOW to improve the soundstage imaging.

So I would not write off ESLs just because some things about them are counter-intuitive. If you have questions about whether a certain ESL will work with your ARCs, all you have to do is ask... I can tell you though that the combo will be good with Quad ESL57s and 63s, you will want the ZEROs with their later models, similarly with nearly all MLs. You will be able to drive Sound Labs directly no worries (however you will want the latest version of the backplate as it corrects a crossover error, making the speaker a lot better sounding and easier to drive), also King, Audiostatic and Accoustat. You will need a set of ZEROs with the Sanders ESLs as they are low impedance.

Also, your amp will be able to keep up with solid state amps, often with the ability to play with as much power as solid state amps of considerably higher power rating. This assumes the match is good (meaning that even if a set of ZEROs is needed, this will still be true).

Theory helps one to play the game well, but ya still gotta play it.

Autoformers in finished boxes showed as costing over a grand. A barebones version would be less i suppose. Es speakers can be pricey, so its all relative i suppose.

"I will say this. Any interest I had in trying ESLs is gone. It seems that amp/ESL compatibility is counter-intuitive. So I'll stick with what I have." Bifwynne

If you have not experienced a well done ESL system, you are missing out on the best! If you are located close enough to be practical (N. California), you are welcome to come hear mine.

****Btw, to the point about going with one's ears. I've been switching between my amp's 4 and 8 ohm output taps. For various technical reasons that I am not going to get into, I would have surmised that the 4 ohm taps would have been the preferred taps. But it just isn't always the case. At least that's what my ears tell me. So much for any notion of "faithful sound reproduction." ****

That was PRECISELY my point. However, I consider what my ears tell me to be correct and the more "faithful sound reproduction"; and what I may have surmised due to theory as secondary in importance. As always, trust the ears; unless we smell smoke, of course :^)

Mapman, I would suggest to you that that reflects how the our hearing responds to a flat frequency response. The flat frequency response is a base line. Deviate from the baseline and our hearing would deviate accordingly.

The ear sensitivity chart shows why what measures as flat
response is not heard as flat response normally, It
illustrates why what measures as flat frequency response
may be perceived as bright.

A lot of mass produced SS gear feature things like filters,
loudness controls, and other tonal adjustments that don't
really work that well as a means of addressing this. Tube
amps in some cases may be better suited by their nature to
help compensate for how our ears hear.

Atmasphere always talks about how most amps do not address
how our ears actually work, which is a valid point. He
tends to focus on brightness from odd order harmonics due to
NF in particular, but I guess I'm suggesting there is more
to it perhaps than just that.

I am standing down. I read all the posts and respect the good intensions and credibility of all the folks who contributed to this OP.

My sense of the issue is purely academic. I'm still trying to get my arms around "simple" electrical compatibility concepts involving amps and conventional/cone speakers. Electrostats seem like a horse of a very differnt color.

I will say this. Any interest I had in trying ESLs is gone. It seems that amp/ESL compatibility is counter-intuitive. So I'll stick with what I have.

Btw, to the point about going with one's ears. I've been switching between my amp's 4 and 8 ohm output taps. For various technical reasons that I am not going to get into, I would have surmised that the 4 ohm taps would have been the preferred taps. But it just isn't always the case. At least that's what my ears tell me. So much for any notion of "faithful sound reproduction."

Well Stanely, "... that's another fine case" where changing speakers may be an exercise in futility.

Cheers and Happy Holidays.

Bruce