Electrostatic speakers?

[AdamG]

QED=?

 

[Blumlein 88]

Acoustat 'solved' vertical beaming by making the panels about six feet high. So you could stand up and sit, and that part of the image was relatively stable. But you still had the problem of horizontal dispersion, which just wasn't there. I recall moving slightly off axis; it was as if one of the loudspeakers suddenly turned off. Maybe not that bad, but it was definitely a 'one seat' loudspeaker.

To work out the horizontal dispersion they made the Model 3 and 4, which were really wide. But they didn't sound as coherent IMO as the Model 2 variants.

The original Acoustat X featured a direct coupled tube amp supplying high voltage to the panels. But that design was evidently unreliable in the field, and people wanted to use their own amps, so later models had a transformer on the back base of the unit. I found the dedicated Acoustat FET amplifier suitable for driving them.

The last models featured integrated woofers in the base, but didn't really integrate well. It's quite difficult to seamlessly blend a dynamic driver sub to an electrostatic.

Actually the Acoustat model 2 and 2+2 were worse than a flat panel. Internally each panel was angled very slightly outward. The resulting lobe was more picky about position than if both panels were flat facing straight ahead. Quite literally one seat left or right and you mostly heard only one channel.

 

[watchnerd]

QED=?

quod erat demonstrandum

 

[maverickronin]

QED=?

quod erat demonstrandum

It is demonstrated / What was to be shown

 

[T.J. McKenna]

I started with Quad ESL63s, living with just the panels for quite a while. Loved them for all the reasons people have already pointed out. But eventually I became dissatisfied with the "ghostly" presentation I find form all electrostatic speakers. It's like "seeing" images of instruments through a portal, but I don't "feel" the sound, as if they are actually moving air in the room. Every time I set up a smaller pair of box speakers to compare, the difference was pretty stark with the box speaker sounding more palpable, dense, dynamic and "air moving." And that was the case even though the box speakers had more limited low frequency range than the ESL.

I did try adding subs, but it only made the range covered by the sub sounding dynamic - the panel portion still had that ghostly detached sound.
Later I added the dipole Gradient subs made especially for the 63s. Best stat/dynamic driver match I've yet heard. Still...didn't have that top to bottom seamless punch and palpability of the average box speaker.

So I moved on. And like almost all who started out with Quads or stats, searched for a box speaker that could get me the best of both worlds - the "disappearing" act of the quads as sound sources, the sense of transparency and fine detail, but with the guts of dynamic speakers.

I found plenty of dynamic speakers that got satisfyingly close to that ideal. But I still love hearing a stat or panel speaker whenever I can. Stats are a lovely place to visit for me, but no longer home.

(Though it's killing me that someone I know actually offered me their ESL 57s for FREE - my favorite panel speaker and one I"d love to have around, but they just wouldn't fit in to my room situation).

I've never found a hybrid stat speaker satisfying, which included hearing plenty of the ML speakers, as I still hear that dynamic discontinuity - put on Rush and it's "rockin'" in the bass where the dynamic sub is covering, but goes all transparent and ghostly in the mids up where the guitars, vocals etc are.

But in no way do I propose my own subjective feelings indict anyone's love of stats or hybrids, as I can totally understand the appeal!

My God! Did somebody else just describe ESL sound as "ghostly"?!!!! I've been doing this for years and everybody just looks at me uncomprehendingly, as though I'm making this up. To me, ESL's always sound as if there's nothing "solid" producing the sound. It's as though the "real", substantial, kick-it-and-your-foot-hurts, instrument producing the sound has disappeared and all that's left is the "wraith" or "shade". If you tried to touch the instrument your hand would go right through it. My theory is that this is the result of the very unnatural way ESL's produce sound. With real instruments sound is generated by a sudden disturbance of air from a point. Think of a guitar string being plucked; the string may move half an inch or more. So your reproducer should try to emulate the same thing: a large movement of air at the specific frequencies from a point. Horn speakers can do this; conventional dynamics in boxes less so; planars even less. And ESL's? How far can the diaphragm move? A matter of millimetres at maximum excursion. So to get some semblance of spl output they have to spread the sound over a large area; in other words, in a manner completely at odds with the original mode of sound generation. Is it any wonder it sounds a trifle weird? Now, I'm not a scientist and not even a particularly well-informed amateur so please don't bite my head off at my naivete. Think of me as an impertinent whelp just trying to understand.

And I agree with Matt that, despite my criticisms, ESL's do offer an alluring and (dare I say it) "magical" sound on appropriate material and I can appreciate why their supporters love them.

 

[T.J. McKenna]

It is demonstrated / What was to be shown

A useful rhetorical trick is to make some outlandish assertion and follow it with "QED". Works some of the time.

 

[Blumlein 88]

My God! Did somebody else just describe ESL sound as "ghostly"?!!!! I've been doing this for years and everybody just looks at me uncomprehendingly, as though I'm making this up. To me, ESL's always sound as if there's nothing "solid" producing the sound. It's as though the "real", substantial, kick-it-and-your-foot-hurts, instrument producing the sound has disappeared and all that's left is the "wraith" or "shade". If you tried to touch the instrument your hand would go right through it. My theory is that this is the result of the very unnatural way ESL's produce sound. With real instruments sound is generated by a sudden disturbance of air from a point. Think of a guitar string being plucked; the string may move half an inch or more. So your reproducer should try to emulate the same thing: a large movement of air at the specific frequencies from a point. Horn speakers can do this; conventional dynamics in boxes less so; planars even less. And ESL's? How far can the diaphragm move? A matter of millimetres at maximum excursion. So to get some semblance of spl output they have to spread the sound over a large area; in other words, in a manner completely at odds with the original mode of sound generation. Is it any wonder it sounds a trifle weird? Now, I'm not a scientist and not even a particularly well-informed amateur so please don't bite my head off at my naivete. Think of me as an impertinent whelp just trying to understand.

And I agree with Matt that, despite my criticisms, ESL's do offer an alluring and (dare I say it) "magical" sound on appropriate material and I can appreciate why their supporters love them.

I had the obverse view. Cones are trying to produce room filling sound at a very small spot of a cone. The sound intensity at the surface has to be extremely high. High enough you have the air in a non-linear zone. Spreading everything out over the big ole panel keeps surface sound intensity low where air remains linear.

 

[watchnerd]

A useful rhetorical trick is to make some outlandish assertion and follow it with "QED". Works some of the time.

Mathematical proofs is the less theatrical usage.

 

[milezone]

In my mind I prefer electrostatic panels to other speakers I've listened to. I've owned Quad 57s (some of the finest), and Acoustat X with direct drive amplifiers (also some of the finest if modified with an updated enclosure and improved circuitry), and KLH9s (don't bother). I've listened to many including Apogee Studio Grands, Martin Logans, King Sound, Quad 63s, etc. And also many of high end audiophile speakers including Kharma Enigmas (nice), Magicos (meh), Wilsons (junk). If they weren't so impractical size and maintenance wise I'd still own a pair -- probably Quad 57s or maybe something contemporary. I own mostly Genelec speakers now and have never compared directly so I can't speak to how the two fare against one another. Contrary to what another poster said, the hype is real in my opinion. In my recollection my most enchanting listening experiences have been with electrostatic speakers.

 

[mhardy6647]

There are 1,051 forum members.

There are 66 entries listed for sale around the world right now, and that includes parts, manuals, and other bits:

https://www.hifishark.com/model/quad-esl-57

In North America, there are a grand total of 9 entries.

Doesn't seem like the supply is high enough for everyone to own a pair.

QED right back at you, buddy.

Drat.
Never expected this to go quantitative!

 

[Duke]

I believe the curved electrostatic panel was invented by none other than Roger Sanders. He has since changed his views and manufactures loudspeakers with flat electrostatic panels that are designed to be "beamy."

My understanding is that a curved panel places more stress on the diaphragm than a flat panel does.

You can imagine a curved panel as a section of an expanding cylinder. When the diaphragm moves forward, it gets tensioned. When it moves backward, the tension is relaxed. Therefore a stronger diaphragm is needed than is the case with a flat panel, and one of Gayle Sanders' innovations was a sufficiently strong diaphragm to make that beautiful continuously-curved panel of the Martin Logans practical. Handing off the bass excursions to a separate woofer section helps.

SoundLab gets around this issue by using a faceted-curved diaphragm, made up of many flat facets, which also enables larger coverage angles. Roger West told me that during initial product development (back in the 70's) he experimented with uniform coverage angles all the way out to 180 degrees, and 90 degrees was preferred. Today most of his large fullrange models are 45 degrees (which increases the efficiency within the coverage pattern), with 90 degrees available as an option.

I am also a huge fan of Roger Sanders' work, it just so happens that my personal listening style and priorities are more aligned with the much wider sweet spot enabled by SoundLab's's approach. I'm not sure anything images as holographically as a well set-up pair of Sanders Sound speakers, and I've seen Roger Sanders further reduce their already minimal early reflections by using a diagonal or semi-diagonal setup geometry. That's also what Floyd Toole did in one of his Canadian listening rooms.

Roger West, Gayle Sanders, Roger Sanders...

 

[MattHooper]

I used to occasionally listen to double-stacked ESL-57s at an acquaintance's house. Those were fun! Talk about a wall of sound!
Also enjoyed the big full range SoundLabs when a local shop had them for awhile.

 

[XeCutor]

These are my electrostats. I bought them new around a decade or so ago. They're from a Dutch company called Final Sound that doesn't exist any longer. These are their 400i model which was one of the smaller ones, but not the smallest. Their largest, 1400i were door-sized and quite impressive. Their claim to fame, I was told, is that their panel is split up into vertical sections making the beam width less narrow and widening the sweet spot a bit compared with the alternatives at the time. (Edit: Also being relatively narrow overall helps) I think it works pretty well. The subwoofer next to it is from the same manufacturer and matched in terms of crossover, ideally you'd have two but I could only afford one at the time (both in terms of space and money).

 

[Sir Sanders Zingmore]

and I've seen Roger Sanders further reduce their already minimal early reflections by using a diagonal or semi-diagonal setup geometry.

@Duke can you expand on this, what do you mean by the geometries you describe?
Thanks

 

[JustAnandaDourEyedDude]

My God! Did somebody else just describe ESL sound as "ghostly"?!!!! I've been doing this for years and everybody just looks at me uncomprehendingly, as though I'm making this up. To me, ESL's always sound as if there's nothing "solid" producing the sound. It's as though the "real", substantial, kick-it-and-your-foot-hurts, instrument producing the sound has disappeared and all that's left is the "wraith" or "shade". If you tried to touch the instrument your hand would go right through it. My theory is that this is the result of the very unnatural way ESL's produce sound. With real instruments sound is generated by a sudden disturbance of air from a point. Think of a guitar string being plucked; the string may move half an inch or more. So your reproducer should try to emulate the same thing: a large movement of air at the specific frequencies from a point. Horn speakers can do this; conventional dynamics in boxes less so; planars even less. And ESL's? How far can the diaphragm move? A matter of millimetres at maximum excursion. So to get some semblance of spl output they have to spread the sound over a large area; in other words, in a manner completely at odds with the original mode of sound generation. Is it any wonder it sounds a trifle weird? Now, I'm not a scientist and not even a particularly well-informed amateur so please don't bite my head off at my naivete. Think of me as an impertinent whelp just trying to understand.

And I agree with Matt that, despite my criticisms, ESL's do offer an alluring and (dare I say it) "magical" sound on appropriate material and I can appreciate why their supporters love them.

Your theory sounds plausible. I think you may be on to something there, that has to my knowledge not been widely disseminated as a notion or research, if it has been previously conceived of or researched at all by others. If it turns out to correspond to any real physics, it may speak to the suitability of electrostats for many acoustic instruments (edit: where the sound is made principally by resonance boxes with larger surface area and lesser excursion, or by continuous tone wind instruments). Whereas electrostats have a harder time reproducing amplified musical instruments originally played in performance through dynamic speakers at high driver excursion (punch) in the lower frequencies. I tended to use the adjectives "wispy" and "ethereal" in my mind, but "ghostly" is good too, though this perceptual attribute of electrostat sound is not pronounced and is possibly just the obverse face of the clarity of their sound for ears that are trained on dynamic speakers or headphones.

 

[Blumlein 88]

Your theory sounds plausible. I think you may be on to something there, that has to my knowledge not been widely disseminated as a notion or research, if it has been previously conceived of or researched at all by others. If it turns out to correspond to any real physics, it may speak to the suitability of electrostats for many acoustic instruments. Whereas electrostats have a harder time reproducing amplified musical instruments originally played in performance through dynamic speakers at high driver excursion (punch) in the lower frequencies. I tended to use the adjectives "wispy" and "ethereal" in my mind, but "ghostly" is good too, though this perceptual attribute of electrostat sound is not pronounced and is possibly just the obverse face of the clarity of their sound for ears that are trained on dynamic speakers or headphones.

Sam Tellig would say, "there is no there...there."

 

[JustAnandaDourEyedDude]

Sam Tellig would say, "there is no there...there."

Yes, that probably applies here. But it is a notion to consider rationally, as to whether the induced particle motions of the fluid during large excursions of the driver or musical instrument surface can themselves produce audible secondary acoustic waves through self-interaction or interaction with solid surfaces, whether this might happen with the original instrument or during reproduction with a dynamic driver versus an electrostat. There is likely no there...there, but I cannot come up with a reason to dismiss the notion right off the bat.

 

[andreasmaaan]

Yes, that probably applies here. But it is a notion to consider rationally, as to whether the induced particle motions of the fluid during large excursions of the driver or musical instrument surface can themselves produce audible secondary acoustic waves through self-interaction or interaction with solid surfaces, whether this might happen with the original instrument or during reproduction with a dynamic driver versus an electrostat. There is likely no there...there, but I cannot come up with a reason to dismiss the notion right off the bat.

I'm not sure if I understand your idea correctly. Are you speculating that air particles directly in front of a dynamic transducer may be accelerated to such high velocities that the air no longer remains laminar?

 

[anmpr1]

I own a pair, it wasn't hard. There aren't that many folks on this forum.

The problem, of course, with owning a fifty or sixty year old Quad that is sourced second, third, or fourth hand is a) is it intact electro-mechanically and b) can you get it serviced to spec, and finally c) are you willing to pay what it will cost to have this done?

Of course these questions are not unique to Quad, and must be asked of any old equipment. However it is a lot easier and cheaper to recone an old woofer with a bad surround, or replace a blown tweeter than it is to satisfy the three criteria outlined above for a Quad.

 

[JustAnandaDourEyedDude]

I'm not sure if I understand your idea correctly. Are you speculating that air particles directly in front of a dynamic transducer may be accelerated to such high velocities that the air no longer remains laminar?

My picture is more nebulous than that. I just thought that there might be something to McKenna's intuition that a smaller-area larger-excursion (and therefore higher velocity for a given frequency) driver may produce more of something that audiophiles label a "punch" (whether this is a real thing or not is of course debatable) and associate with dynamic drivers versus other types. For a given SPL, the total acoustic energy imparted is the same, but it is denser at creation by a smaller dynamic driver than a larger electrostatic driver. I am speculating as to whether any such punch could be the perception of secondary sound waves caused by faster and larger particle displacements. I do not have a feel for the actual physics or numbers involved.

My picture for the past many years is the idealized textbook one of a vibrating flat plate flush with a wall wherein the laminarity assumption is built-in and the particle motions are too small to affect the state of the ambient fluid medium (and so linearity is built into the model). I am unaware of the research that may have been done into modeling non-idealized driver geometry and motion and more realistic fluid motion. So turbulence and interaction with solid boundaries are possibilities in my mind that my current state of ignorance of the actual physics involved prevents me from ruling out. Certainly, the classical transition Reynolds number range (based on mean velocity, diameter, viscosity and surface roughness) for flow in a pipe would be inapplicable here. The fluid velocity field in the vicinity of the driver is not likely to be in a laminated pattern, given that the fluid motion is oscillatory and the driver motion during typical music program material is not periodic and the amplitude changes continually, and that the driver displacement is not uniform across its surface area (there are edge effects) and that there are oscillating boundary layers propagating from cabinet or headphone walls towards the center of the driver. I do not know which, if any, fluid instability types may arise. All of the non-idealities may not make a whit of difference, but I am unable to estimate whether smaller-area higher-excursion drivers exaggerate any of the non-idealities to the point of making an audible difference, a sound signature of typical dynamic drivers versus typical electrostats.