Electromotion ESL panels fading issue.

[AuBrisbane]

Have you tried emailing Ron at Martin Logan service? Usually he comes up with those documents pretty fast. If you just use their service email, he should be the one that helps you. Ron seems to handle most things in service. He's great.

Thanks Robert,

Yes , got quick reply with instructions attached from Ron.

Now it is back to work.
Wish me luck.

Cheers.
Zoran

 

[AuBrisbane]

Hi Zoran,

Humidity may or may not contribute to deterioration of the diaphragm's conductive coating. ML says no-- but it's fair to question that, given ML's vested interest and the number of owners posting about their panels fading.

The coating is vapor-deposited indium tin oxide, which is insoluble in water but I don't know if that rules out corrosion from humidity.

Humidity significantly reduces the dielectric break-down voltage of air, which increases the risk of arcing and also increases the rate of charge dissipation from the diaphragm to surrounding air.

Logically, the bias supply should replenish charge faster than it's dissipated away, so humidity would have to be really high (as in no AC on a hot rainy day) before it's a problem.

A greater concern would be conduction paths (diaphragm-to-stator) due to humidity moistened dust built up along the edges of the spars and edge spacers. This can drain charge off the diaphragm faster than the bias supply can replenish it, resulting in partial to complete volume loss and/or destructive arcing.

I absolutely cringe at the thought of washing a panel with water, but I suppose if the panel is dying, there's nothing to lose. In cases where this actually restores volume, it could only have done so by washing away the aformentioned conduction paths.

That reminds me:
If anyone does wash a panel with water + dishwashing liquid, it's imperative that all soap residue is thoroughly rinsed off, because it's conductive!

Dish soap makes an effective DIY diaphragm coating, which gives excellent volume and it's cheap (attracts dust, though).

Water intrusion from panel washing would tend to corrode the copper foil charge strip. So; I would only advise washing a panel as a last resort.

Since I build ESLs as a hobby, I would just rebuild both panels if I had one fading (it's not rocket science).

Speaking of...
Now that you have new panels for your speakers, I would vacuum them quite often. And you might consider having some acoustically transparent sock covers sewn up.

All of my DIY ESLs have cloth grills front & back.

And BTW...
I would hang on to those old panels if I were you. You might want to rebuild them someday.

You might even get lucky and successfully separate the stators without damaging the diaphragms-- in which case; you could solvent clean and re-coat the original diaphragms with Licron Crystal ESD spray-coat, re-assemble the panels, and enjoy the music.

FYI:
On some ML models, the stators are only bonded at the top and bottom edges, with the side edges un-bonded and held together by the speaker frame.

In all models, the diaphragm is bonded to the rear stator.
At panel top/bottom edges, the component stack-up [rear to front] is:

Rear stator
Rear urethane foam tape spacer/adhesive
Diaphragm
Front urethane foam tape spacer/adhesive
<<<<< (separate panel here) >>>>>
Front Stator

1. Attempt to pry apart and separate the front stator at the forward stator/spacer bond line.
2. If it doesn't want to come apart easily, then use a box knife to cut thru the front urethane foam spacer (close the the front stator to avoid damaging the diaphragm).

Here's a post that goes into more detail about ESL panel construction:
https://www.martinloganowners.com/threads/panel-rebuild-guide.19749/#post-210111

Thanks Jazzman,

It is Winter in Australia now and humidity is at ideal level of 50-60%.
How does it affect my ESL?
It is like Night and Day in regards to clarity, sound is clean and detailed, compared to Summer time when humidity normally hover around 70-90%.
Panels replaced were made in China (not sure if that makes any difference) but sound I am getting is far from sound experienced on other ML ESL hybrid speakers at various shows I have visited.

New panels + HV Power supplies are shipped from Canada, so I guess it should be close to how it
is expected to sound.

Me going for panel rebuilding, I don't think so. I may keep old one as a spare (just in case).

Thanks for your detailed work and your kindness.

Kind regards from wintery Australia (+25C today and some dare to call it Winter?)

Zoran

 

[Jazzman53]

Thanks Jazzman,

It is Winter in Australia now and humidity is at ideal level of 50-60%.
How does it affect my ESL?
It is like Night and Day in regards to clarity, sound is clean and detailed, compared to Summer time when humidity normally hover around 70-90%.
Panels replaced were made in China (not sure if that makes any difference) but sound I am getting is far from sound experienced on other ML ESL hybrid speakers at various shows I have visited.

New panels + HV Power supplies are shipped from Canada, so I guess it should be close to how it
is expected to sound.

Me going for panel rebuilding, I don't think so. I may keep old one as a spare (just in case).

Thanks for your detailed work and your kindness.

Kind regards from wintery Australia (+25C today and some dare to call it Winter?)

Zoran

I'm reminded that the original Quad 57 used a nylon coating on its diaphragm, which is only conductive because it's hygroscopic (absorbs water), and so it could hold more charge and actually play louder in humid conditions.

But nylon isn't used anymore, and current diaphragm coatings are less affected, or not at all by humidity.

More charge on the diaphragm gives greater drive force, resulting in greater dynamics and output. And the opposite is true when charge is reduced.

Charge is constantly being dissipated into the surrounding air, and the rate increases in higher humidity, as the air becomes more conductive-- hence; less charge on the diaphragm giving lower drive force, reduced dynamics and reduced output.

Also, any significant dust built up along the spars and periphery spacers becomes conductive in humid conditions and drains charge off the diaphragm and into the stators.

If the bias supply can't replenish the charge across the high-resistance (about 1MOhm) diaphragm faster than it's being dissipated, then dynamics and output must suffer.

I hadn't given much thought to effects beyond charge/dynamics/output loss. But its not unreasonable to wonder whether cranking the volume up to compensate might be pushing the transformer into saturation, resulting in higher stress for the amp, and possible effects on sonic character. Just speculating...

 

[Jazzman53]

I suspect but can't prove it, and ESL manufacturers might be reluctant to confirm it if it were true:

We ponder whether humidity plays a part, but panels losing volume over time could be solely the result of the high voltage corona progressively eroding/damaging the diaphragm's conductive coating.

The bias supply plugs into a wall outlet which would keep the diaphragm energized 24/7 were it not for a music sensor circuit on newer ML models that only energizes the bias supply when a music signal is detected (pondering the reasons for adding this feature?).

My DIY ESLs do not have this feature, so I have my bias supplies plugged into switched outlets which come ON/OFF with the amps, and I only turn the amps ON when listening to music.

The photo below shows high-voltage corona streaming off sharp points on a metal pinwheel charged to 10kV. The sharp points focus the corona to a visible intensity.

The same coronal discharge occurs across the surface of a charged diaphragm, although at a much lower rate and intensity that isn't visibly apparent.

 

[Robert D]

I suspect but can't prove it, and ESL manufacturers might be reluctant to confirm it if it were true:

We ponder whether humidity plays a part, but panels losing volume over time could be solely the result of the high voltage corona progressively eroding/damaging the diaphragm's conductive coating.

The bias supply plugs into a wall outlet which would keep the diaphragm energized 24/7 were it not for a music sensor circuit on newer ML models that only energizes the bias supply when a music signal is detected (pondering the reasons for adding this feature?).

My DIY ESLs do not have this feature, so I have my bias supplies plugged into switched outlets which come ON/OFF with the amps, and I only turn the amps ON when listening to music.

The photo below shows high-voltage corona streaming off sharp points on a metal pinwheel charged to 10kV. The sharp points focus the corona to a visible intensity.

The same coronal discharge occurs across the surface of a charged diaphragm, although at a much lower rate and intensity that isn't visibly apparent.

View attachment 24450

I wonder, why does the coating erode? Maybe the electrical discharge heats it up enough to do that slowly? Has anyone ever measured the heat of the diaphragm?

 

[Jazzman53]

I wonder, why does the coating erode? Maybe the electrical discharge heats it up enough to do that slowly? Has anyone ever measured the heat of the diaphragm?

Good question.... I'm not aware of any temperature measurements, and I haven't attempted any.

If there is erosion/damage occurring due to the corona, I'm thinking it would have to be by cooking away the coating or rendering it non-conductive by making or breaking chemical bonds within the coating.

 

[Robert D]

Good question.... I'm not aware of any temperature measurements, and I haven't attempted any.

If there is erosion/damage occurring due to the corona, I'm thinking it would have to be by cooking away the coating or rendering it non-conductive by making or breaking chemical bonds within the coating.

Yeah, heat related. I wonder.

 

[AuBrisbane]

Hi Robert and Jazzman53,

Issue with faded ESL Panels finally solved two days ago. Last six months was period of procrastination " I'll do it next week" kind.
The whole process coincided with my Yamaha AVR AVENTAGE RX-A1030 starting to experience known issue with DSP Board and Texas Instruments provided CHIP.
Nearly 10 years old and I decided to replace it with brand new Yamaha AVR RX-A6.
Before doing anything on ML Electromotion ESL I have tested them connected to new Yamaha AVR and got exactly same result, very, very dull sounding panels.
It is summer in sub-tropical Brisbane, Australia and humidity is hovering above 80%. Not a favourable environment for ML ESL panels (Yes, room is air-conditioned).
Got pair of new panels from Martin Logan Canada in April 2023 and pair of Power Supplies, as well.
Followed instructions and now I have to train my ears and brain for such brightness (I have forgotten how they sounded when I got them (10 years ago for the first time) as this is third set of panels replaced in 10 years.
Not sure if it matters but I have to mention that panels and Speaker cabinets were coming out from China, will see if one made in Canada will last longer.
Replacing panels is no brainer but replacing HV power supply (High Voltage) was a challenge as some wires are so short that removing bottom cabinet cover was almost impossible without removing bass-reflex cone first.
Another challenge was glued plug for cabinet LED and glued securing screw for HV Power supply board, not easy to remove and not damage Transformer insulation or other board in process.

Thank you very much for all your help in this matter.

Kind regards.
Zoran