Electrostatic speakers?

[steve f]

Forgive my ignorance. If you sit closer than your 12 feet, is the sweet spot wider or narrower?

The closer you sit, the narrower the sweet spot. Roger Sanders purposely designed his speakers to have a narrow pattern which mitigates room interactions. It’s possible to change the image perspective by moving just a couple of inches , mostly left or right, but depth equidistance matters too. They are a difficult speaker to set up, but when you get it right, wow.

 

[DavidEdwinAston]

The closer you sit, the narrower the sweet spot. Roger Sanders purposely sesigned his speakers to have a narrow pattern which mitigates room interactions. It’s possible to change the image perspective by moving just a couple of inches .but when you get it right, wow.

Thank you steve.
I am perhaps 7 feet from each of my current speakers and might possibly have to sit on the pavement! (Sidewalk)! To get good positioning for the Sanders. I can believe that from the ideal position, they are sensational. And not huge money!

 

[Eytsch]

I am averse to used speakers - I don't know what next more-extreme word after "averse" is - but that would be my feeling about used pair of ESLs.
Aren't there some major reliability issues with electrostatics in (or due to) humid environments?
The geographic location where this used ESL pair (you are considering) were used may be a worthy consideration before purchase.

Good point. I have a story to back it up:

A few years ago I bought a pair of used Martin Logan Vantage speakers from a local hifi store. I really loved how they sounded in my setup. They didn't suffer the sweet spot problem I had experienced with smaller/earlier MLs that I had auditioned. I was impressed by the wide sound stage, even the bass was surprisingly full and alive. I really wanted to keep them as my main speakers.

However there was this constant hiss/crackle sound coming from R that I hadn't noticed at the store. It wasn't audible during normal playback, but was there like tinnitus, noticeable at standby or even during quieter audio segments. The store recommended cleaning the panels with a vacuum, which I did twice to no avail. They offered to contact ML for repairs, or take them back. I didn't have time to deal with repairs, so I (very sadly) returned them.

This would have been a more painful story buying online sight unseen / sound unheard.

 

[Justdafactsmaam]

If you want high volumes and/or pounding bass, then the 'stat is not for you. They're too delicate for that. I think one reason bass is anemic in 'stats because the speaker is free standing, the way a boxless woofer driver in the open would be. Cancellation severely attenuates the lows.

Sanders 10Es can deliver 120+ db SPLs with minimal distortion. They are bulletproof. They are also hybrids so they have none of the inherent problems with dipole bass.

 

[Justdafactsmaam]

I was an ESL builder for many years, and I concede that I've become quite opinionated about what I think works, and doesn't.

My first ESLs were hybrids, with the woofer in a transmission line enclosure, and a perf-metal stator, flat panel ESL. These beamed like a lasers but sounded great in their minuscule sweet spot.

My latest ESLs are also hybrids, but with wide-dispersion, symmetrically segmented wire-stator flat-panels, and an open baffle woofer.

Anyone who hasn't experienced sitting at the focal point of a pair of an un-segmented flat panel ESL's, like Sanders' speakers, would have no reference to imagine how directional they are, or how magical their imaging is at the focal sweet spot. Any description its sound should include the caveat "in the focal sweet spot" because its sound changes profoundly as one moves outside its tightly focused sweet spot.

I don't consider beaming a fault, insofar is it gives pinpoint imaging that seems rather magical... but it's not good for entertaining guests.

It's been my experience that a woofer mounted in a sealed or ported enclosure (like the ML's) can't blend seamlessly with the ESL panel in the critical crossover-overlap.

My engineer's mind is also critical of the asymmetric drive forces and hoop restraint imposed by curving an ESL panel, which hurts efficiency but I can't say that it's audibly objectionable.

I've also found that a transmission line woofer blends much better, but an open baffle-mounted woofer with low inductance (< 0.8mH) and Qts =/< 0.5 blends so seamlessly that it sounds like a single driver. The downside with an OB is that it rolls off the bass higher (i.e. the dipole roll-off) so it needs subs < 60Hz.

My 2 cents...

Race cars don’t come in 4 seat configurations. If one wants state of the art sound quality from two channel stereo it’s going to happen in one seat.

 

[egellings]

Sanders 10Es can deliver 120+ db SPLs with minimal distortion. They are bulletproof. They are also hybrids so they have none of the inherent problems with dipole bass.

'Stats work well when augmented with a cone type woofer.

 

[Jazzman53]

Race cars don’t come in 4 seat configurations. If one wants state of the art sound quality from two channel stereo it’s going to happen in one seat.

I don't disagree with that, but when you need a bus (guests drop by), a race car won't do.

Maybe a convertible? (a segmented ESL with switch-selectable wide and narrow dispersion modes):

A Segmented Wire Stator ESL with Selectable Wide/Narrow Dispersion

I was so inspired by my friend Ken Seibert's ESL project that I decided to have a go at building a pair of segmented wire stator ESL's mysel...

jazzman-esl-page.blogspot.com

Those were butt-ugly but they worked quite well. I've moved on to prettier ones now

 

[Jazzman53]

Good point. I have a story to back it up:

A few years ago I bought a pair of used Martin Logan Vantage speakers from a local hifi store. I really loved how they sounded in my setup. They didn't suffer the sweet spot problem I had experienced with smaller/earlier MLs that I had auditioned. I was impressed by the wide sound stage, even the bass was surprisingly full and alive. I really wanted to keep them as my main speakers.

However there was this constant hiss/crackle sound coming from R that I hadn't noticed at the store. It wasn't audible during normal playback, but was there like tinnitus, noticeable at standby or even during quieter audio segments. The store recommended cleaning the panels with a vacuum, which I did twice to no avail. They offered to contact ML for repairs, or take them back. I didn't have time to deal with repairs, so I (very sadly) returned them.

This would have been a more painful story buying online sight unseen / sound unheard.

It's buyer beware when buying a used ESL. Too often the seller knows there's a deterioration in the speaker but sells it anyway, before it stops playing entirely, with no regard for the unwary the buyer who gets stuck with a lemon.

An ESL's Achilles heel is its diaphragm coating losing conductivity, which causes the panel to lose volume over time.

My personal belief is that the coating is being slowly cooked off the diaphragm anytime the speaker is playing, and if so, a panel that doesn't get played much should last longer than one that gets played more often.

I would also guess that ESLs with exposed panels (like the ML's) that are not vacuumed often collect a dust buildup which holds moisture and creates shorting paths that can drain charge off the diaphragm faster than the bias supply can replenish it, or worse; allow arcing to occur which can cause a sudden and catastrophic failure. So it pays to keep the panels clean. A symptom of this is recurring popping sounds (arcing).

There are only anecdotal reports on life-estimates, which vary greatly. My thinking is that 20 years is all you can expect, no matter how well the speakers were cared for.

I make an exception for Acoustats, which use an ultra-reliable carbon black coating on the diaphragm, and they have arc-resistant insulated wire stators that make these speakers almost bullet-proof reliable.

 

[misterdog]

An ESL's Achilles heel is its diaphragm coating losing conductivity, which causes the panel to lose volume over time.

Proof ?

Or conjecture.

I have heard various theories concerning my Quad 989's

- they have no bass - mount them in steel panels - myth dispelled, the bass is more than ample....

Diaphragm coating is a thread worthy of it's own merits - surely..

esl diapraghm coatings - Google Search

 

[Jazzman53]

Proof ?

Or conjecture.

I have heard various theories concerning my Quad 989's

- they have no bass - mount them in steel panels - myth dispelled, the bass is more than ample....

Diaphragm coating is a thread worthy of it's own merits - surely..

esl diapraghm coatings - Google Search

I will concede that I have no experiential evidence for Quad panels specifically. It may be that Quad uses a coating so robust that it never goes bad. That seems to be the case with the carbon-black coating that
Acoustat used.

There is ample evidence of the coating on ML panels losing conductivity, resulting in the panel losing its output over time, and replacing the diaphragm with a fresh diaphragm and coating is the fix. All you have to do is browse the threads on the ML owners forum and read the complaints to confirm this. Many owners are buying new panels or having the original panels refurbished with freshly coated diaphragms.

According to numerous reports on the ML Forum, 20 years seems to be the max life of an ML panel, although average is shorter.

ML determined that the ionizing charge on the diaphragm was cooking away the coating over time, and this was made worse by the bias supply remaining energized 24/7 (i.e. anytime the AC power cable was plugged into a wall outlet).

ML improved the panel life on later models by adding a sensor circuit that energizes the bias supply only when a music signal is detected. So; when the system turned off after playing, the diaphragm is not being replenished with charge and it leaks away it's charge within an hour or so.

I rebuilt an old ML Theater panel a few weeks ago which had a dead spot (not sound output) on one end of the panel. I knew the cause already, but I confirmed it for the owner anyway, by measuring the conductivity on the diaphragm when I got the panel apart. The dead zone coincided with an area on the diaphragm where the coating was no longer conducting.

My speaker builds don't have a sensor circuit but I do require the owners to plug the bias supply's AC cord into a switched outlet that is only energized when the preamp is ON.

My oldest speaker pair with the Licron coating is approaching seven years old and I haven't noticed a loss of volume yet. Even so; I don't expect it to last more than 20 years. The difference is; I design the panels where I can easily access and re-coat the existing diaphragm without having to replace it.

Having said all that-- your point is well taken, and I now revise my assertion to say that the Achilles heel of a ML panel is the diaphragm coating losing conductivity over time.

 

[egellings]

Has anyone come out with a diaphragm material that is intrinsically slightly conductive, so that a coating need not be applied?

 

[Jazzman53]

Has anyone come out with a diaphragm material that is intrinsically slightly conductive, so that a coating need not be applied?

Sanders' Ultra-Stat white paper states that his diaphragm coating is "embedded within the material". Neither Sanders nor ML discloses what their coatings are but I'm guessing both are using plasma-deposited indium tin oxide, which should be a significant improvement over whatever ML was using on its older models.

Both Sanders and ML refer to their diaphragms as being "coated", which would rule out being an intrinsic property of the film.

I'm not aware of anyone using an intrinsically conductive film.

 

[Duke]

Sanders' Ultra-Stat white paper states that his diaphragm coating is "embedded within the material". Neither Sanders nor ML discloses what their coatings are but I'm guessing both are using plasma-deposited indium tin oxide, which should be a significant improvement over whatever ML was using on its older models.

Both Sanders and ML refer to their diaphragms as being "coated", which would rule out being an intrinsic property of the film.

I'm not aware of anyone using an intrinsically conductive film.

Yes, I am under the impression that Sanders Sound has zero issues with loss of conductive coating.

I don't know what coating SoundLab uses, but I've never had loss of conductive coating be an issue for myself or any of my customers in twenty-five years or so.

[Edited to add: Current generation SoundLabs with "PX" panels have a thin Teflon layer over the conductive coating which protects the coating from the environment.]

Even if the conductive coating is intact localized charge reduction can still occur if there are leakage paths, perhaps due to dust, or moisture accumulations in high humidity conditions. SoundLab uses a strip of copper around the perimeter of the panel which charges the panel from its perimeter rather than from a single location. This maintains a uniform charge across the panel even if there is a charge leakage somewhere on the panel.

 

[Blumlein 88]

I don't know the particulars, but Soundlab's PX coated panels are said to be exceptional. The owner says they can be considered heirloom speakers that can be passed down to subsequent generations with the PX panels.

In my experience the other part of ESL's that need attention are the high voltage supply to the panels. Over time they will go out even if the panels are good. Most use some series of voltage doublers. I think Soundlab now uses an off shelf adjustable high voltage supply. Or at a minimum some have found one they can put in their speakers. I would assume those would work with other ESLs. Don't know of a reason they would not.

 

[misterdog]

I don't know the particulars, but Soundlab's PX coated panels are said to be exceptional. The owner says they can be considered heirloom speakers that can be passed down to subsequent generations with the PX panels.

I love the sound of marketing speak.

In the UK we only have 'best' bitter and 'premium' lager, though many beers are just mediocre at best.

 

[misterdog]

SoundLab uses a strip of copper around the perimeter of the panel which charges the panel from its perimeter rather than from a single location

As do Quad panels.

Any electrical engineer trying to apply several thousand volts across across a panel from a 'single location' might need a change of career.

 

[misterdog]

The reason that >63 Quad panels fail is the hot melt glue holding the stators to the plastic matrix fails, exacerbated by a lack of structural rigidity, allowing flex within the panels as people move them.

Also, holes in the Mylar membrane caused by arcing and again glue fatigue from the membrane to plastic matrix.

Of note, the rear stator has a fine mesh covering to control the rear wave.

 

[Duke]

The reason that >63 Quad panels fail is the hot melt glue holding the stators to the plastic matrix fails, exacerbated by a lack of structural rigidity, allowing flex within the panels as people move them.

Contributing to the claimed (and ime genuinely improved) longevity of SoundLab's PX panels is the very high structural rigidity of the plastic lattice that the stators are attached to, which prevents this type of failure mode. Earlier generation SoundLab panels were not as rigid and there were stator insulation breakdowns that corresponded with rough handling in shipment. The "PX" generation of panels was designed for commercial use in permanant installations like movie theaters, so they had to be competitive with conventional speakers in ruggedness and reliability.

 

[Jazzman53]

I don't know who came up with the copper foil charge ring idea but it's a good one, and it's been used by DIY builders for many years, including all of my builds since 2008.

Vapor-deposited indium-tin oxide may be the current state of the art in diaphragm coatings, but that process isn't feasible for us DIY builders, so we have to make do with whatever we can find.

Historically, DIY coatings have included rubbed-in powdered graphite, or graphite slurries (messy and difficult to get uniform resistance), carbon-black mixed with a paint binder (very reliable but opaque), wiped-on dish soap (works well but attracts dust), metalized Mylar (way too conductive, prone to arcing), and mixtures containing anionic salts. Of these coatings, only carbon-black paint has proven longevity.

The DIY community now uses anti-static ESD products almost exclusively (Licron Crystal, Staticide, Stat-Clear). These coatings have close to ideal resistance (E7-E9 Ohms) but no one really knows how long they will last.

I've used LIcron Crystal for about 12 years, but I've given away the older panels and I don't know how many are still playing. The oldest wire panels I have kept up with were built in 2015 and the owner says they still play fine. My personal speakers with the Licron Crystal coating are about 5 years old now and I haven't noticed any loss in output. Time will tell....

The Licron is working well so far, but it's not cheap, and I would love to develop a cheap, easy, clear coating that lasts forever. This would be the holy grail.

To the couple of DIY builders out there who claim to have such a coating, and are selling their closely guarded secret sauce, I say this: Yes of course, you have every right to guard your secret for sale and profit, but you probably aren't making a lot of money on it since the ESD products showed up (there aren't that many of us to buy it from you), so why not share your formula with those who would appreciate your benevolence?

The speakers I build were largely enabled by other builders sharing their knowledge with me over many years. So if I had a holy grail coating, I would pay it forward by freely sharing it with the DIY community.

 

[Jazzman53]

I've never had an opportunity to hear the big Soundlabs. The big ones are huge compared to other commercial offerings, and physics tells me their sound has to be really BIG. Someday...