Repanelling ML Clarity's

[neil5m]

I've also bought some 12um PET with an 80A (angstrom) coating of aluminium on it. It is 80% transparent and conductive. I've read the posts of another user who used metallised Mylar and played around with stator spacing to prevent arcing. His was proper metallized with high reflectivity. The one I have is mostly transparent with a light grey tinge. I think they use it for windows. The factory also does 6um but didnt have it in stock. I read on another forum that ML used an ITO based coating. ITO coated is expensive, fragile and not available in 12um. The other option to the ITO which is much cheaper, transparent and available in 6um and 12um would be the aluminium coating which I picked up.

If I use it, I will mask of the sides, top and spar areas with polyimide tape to prevent any leakage to the stators. The Clarity operates at a voltage around 2.5kv which the polyimide can easily handle.

I'm keen to hear from anyone if using lightly metallised PET with polyimide masking will or wont work. I will first try the Statclear from Edson Electronics and should that not work, the metallised PET.

 

[neil5m]

If the coating is failing to conduct the bias voltage as efficiently as before, then yes, increasing the voltage *might* improve volume, but possibly at the risk of causing an even more rapid degradation in the coating. So probably not worth the effort to mess with the bias voltage electronics.

Do you have an electrostatic charge meter? And do you have baseline metrics for recently made vs now?

Here's an old thread on input voltage changes and impact on panel output, it has a discussion of an Electrostatic Voltmeter and HV changes that might be helpful: http://www.martinloganowners.com/forum/showthread.php?4703-More-Volts-More-better-sound/page2

Double-checking that the problem is not the HV electronics is also recommended. Maybe something in them is going, so do measure (carefully).

hi JonFo, I took the panels apart and used the Surface Resistivity (SR) meter on the failed Licron Crystal coating. It was applied a year ago and is supposed to read between 10^6 to 10^9. However, the reading was Insulative i.e. >10^12. I wiped a swab of 99% ethanol over the coating and rechecked. This time the SR meter showed 10^9. However a short while later, it was back to Insulative as the alcohol evaporated. Same result with acetone. Considering the coating is still there, how come it isn't working anymore. Seems odd as it is a polymer urethane based coating which is super tough to clean off a surface. I spent over an hour trying to clean it off the PET with limited success.

 

[neil5m]

Last night I put the stators back together after recoating with Statclear of Edson Electronics in the UK. Very good outcome! There is a slight high pitched hissing coming from the panel but I assume its some leakage which will sort itself out. Its only been a few hours playing but it sounds great! Highs are superb. I'll take the SPL level today and another in a week to see if there are any panel drops.

Experience with Statclear: water based solution, has a soapy liquid feel to it and smells like buttermilk (whey from curds). Very easy to apply with a sponge. Is slightly iridescent from an angle. From the description sent by Neil Woods, it is clear permanent, non migratory, biodegradable, has a SR of 10^7 to 10^9 settling towards 10^7. The SR after drying was 10^7. I'll spray some test areas (window glass) and see how it performs over the longer term. I'm keen to understand how this coating would manage the humidity and dust here in HK. Edson Electronics said that the test coating in their office has maintained its SR even after 4 years.

Other changes made: in the earlier rebuild, I had increased the front stator distance to the diaphragm to 0.8mm from the original 0.6mm. After learning that it affects SPL, I reverted back to 0.6mm.

 

[neil5m]

neil5m,

Just wondering - as per above your orginal spars were 0.6mm (rear) and 0.2mm front and finally you used spars with more thickness (front spar 0.2mm -> 0.6mm).
What is the reason for this? As this triples stator-membrane distance I would expect some audible effect resulting in lower SPL. Can you please let me know how this sounds comparing to orginal ones?

rgds
-jacek

Hi Jacek
You were right, it makes a difference. The 0.8mm distance SPL is lower than 0.6mm. I recoated yesterday and reverted to 0.6mm and it does sound better!

 

[jacek-k-wawa]

Hi Neil,

So what spar thickness you have finally for front and back stators?

Also, what arrangement you have around copper charging strip? I can see 2 possibilities here:
- spray coating on the foil with no copper strip and then glue strip over the coating surface (this requires that copper strip has conductive adhesive)
- glue copper strip on the mylar and then spray coating on the mylar and on the charging strip together.

I used to have option 2 but I am just a bit concerned that connection between coating on the mylar and charging strip may not be durable enough and over the time it may deteriorate so presumably option 1 seems to be better.


BTW - there is a quite interesting discussion in diyaudio.com on hear treatment mylar before it finally gets glued to stators:
https://www.diyaudio.com/forums/planars-and-exotics/103362-diaphragm-heat-treatment.html
As per this discussion heating mylar to near the melting point (around 160 C) does have positive effect on longevity of stretch of the mylar - without this there is a chance that over the time tension could decrease and with this resonant frequency will decrease as well.

 

[neil5m]

Hi Neil,

So what spar thickness you have finally for front and back stators?

Also, what arrangement you have around copper charging strip? I can see 2 possibilities here:
- spray coating on the foil with no copper strip and then glue strip over the coating surface (this requires that copper strip has conductive adhesive)
- glue copper strip on the mylar and then spray coating on the mylar and on the charging strip together.

I used to have option 2 but I am just a bit concerned that connection between coating on the mylar and charging strip may not be durable enough and over the time it may deteriorate so presumably option 1 seems to be better.


BTW - there is a quite interesting discussion in diyaudio.com on hear treatment mylar before it finally gets glued to stators:
https://www.diyaudio.com/forums/planars-and-exotics/103362-diaphragm-heat-treatment.html
As per this discussion heating mylar to near the melting point (around 160 C) does have positive effect on longevity of stretch of the mylar - without this there is a chance that over the time tension could decrease and with this resonant frequency will decrease as well.

Hi Jacek, sorry for the much delayed reply. This time, the front Stator was 0.6mm from the diaphragm instead of 0.8mm earlier. It did work initially with high SPL's and seemed well balanced with the woofer. Maybe it was too close to the stator (could hear arc'ing) on a video I took with mobile phone, see: https://youtu.be/BVr3TD94Lv4
These a few videos I took of a soundtest after coating:
https://youtu.be/cggNfc0DwMo
https://youtu.be/uXRTp34qfG4
https://youtu.be/E_lyLNP4Aek
https://youtu.be/Q6gh-BU9jCs

However (i'll write separate post), the coating has failed in a few days, I'm not sure if it was the closer distance to the stators and it got burned off or what the issue was. I did have a tough time getting the copper strip to stick as the coating was like liquid soap and didnt let the copper strip stick.

Regarding the arrangement for the copper strip, I have done both (following the advice from a group member to prevent coronarisation on the edges of the copper strip where it meets the coating.
1) I coated the panel and left it to dry
2) Put the copper strip on the panel
3) With a brush, rubbed some coating over the top of the copper strip and where it met the panel.

This copper strip did not have conductive glue. My next copper strip purchase will have the conductive glue on it.

Regding the heating of the mylar, WrineX (Joppe Popleen) from DIYaudio said that heating the mylar while its already on the stator causes it to lose tension and when in use go closer to the stators due to the reduced tension. Now I did use heat from a heat gun not knowing all this. Not sure whether I have lost tensioning.

 

[neil5m]

The Statclear 50 Coating failed a week after I coated the diaphragm with it. It initially sounded great with good SPL's and very airy, however in a few days, each segment between the spars started to go soft and eventually dead. With my ear to the stator I did hear a buzzing sound which sounded like arc'ing in a video, See: https://youtu.be/BVr3TD94Lv4 . I think the original stator distance was 0.6mm so I stuck with that. Maybe it was too close and burned off the coating.

For the last time, I'm going to coat with Huzheng Nanotech's RB-048. It is a transparent alcohol based anti-static coating (see the basic data sheet). Lets hope this works for a bit longer.
If this fails too, the last thing I will try is 250A metallised mylar (it has a very light metallised coating on it). The PET is 12um thick. It also has an anti-static coating on it which the company says is permanent. The surface resistivity meter showed a reading of conductive 10^3 so i'm not sure where the anti-static coating is. I used a multimeter to check for continuity on the metallised surface but it did not beep even with the probes-on-coins-kept-apart method.
I also tested 80A metallised mylar, but it did not show any reading. It was as insulative as normal PET. The company said that its possible the coating oxidized immediately since it is so thin hence no reading (?).

Anyway, i'll report on the RB-048 coating as soon as I've completed it.

 

[neil5m]

The company had a bunch of interesting anti-static coatings. There was PTU-078 (polymer + conductive resin, water based) with SR of 10^6-8 which I liked, but required heat and powerful UV curing (3000W 365nm). Another one I liked was RB-9H with an steady SR of 10^9 but was not self-leveling. See the pics and params below:

 

[neil5m]

Ok I took apart the panels again post the Statclear coating which did not work for my rebuild. The coating has worked for many others so it may be something I did wrong. I used the SR meter on the panel and the coating shows largely 10^8, but in some areas 10^10. The copper strip edge had a green powder on it in areas which I guess is the coating burning off along the copper strip. I've since recoated using the RB-048 and this time used copper tape with conductive adhesive. I've also applied the coating twice on the copper strip to make sure it does not burn off.

Positives of RB-048: It was very easy to work with, has a acetone like smell and dries quickly. I applied it with a sponge. I've been using it for the last two weeks now and it sounds very good, a bit high on the upper mids, but overall very good. I'll attach a freq chart from my Anthem ARC later to this thread.

Negatives: It is sharply affected by humidity. The highs literally disappear until I have kept the AC on for at least 10 mins. After that is sounds superb. Humidity here in HK is high and is an ML-killer.

Let see how long this coating lasts!

 

[neil5m]

The Statclear 50 Coating failed a week after I coated the diaphragm with it. It initially sounded great with good SPL's and very airy, however in a few days, each segment between the spars started to go soft and eventually dead. With my ear to the stator I did hear a buzzing sound which sounded like arc'ing in a video, See: . I think the original stator distance was 0.6mm so I stuck with that. Maybe it was too close and burned off the coating.

For the last time, I'm going to coat with Huzheng Nanotech's RB-048. It is a transparent alcohol based anti-static coating (see the basic data sheet). Lets hope this works for a bit longer.
If this fails too, the last thing I will try is 250A metallised mylar (it has a very light metallised coating on it). The PET is 12um thick. It also has an anti-static coating on it which the company says is permanent. The surface resistivity meter showed a reading of conductive 10^3 so i'm not sure where the anti-static coating is. I used a multimeter to check for continuity on the metallised surface but it did not beep even with the probes-on-coins-kept-apart method.
I also tested 80A metallised mylar, but it did not show any reading. It was as insulative as normal PET. The company said that its possible the coating oxidized immediately since it is so thin hence no reading (?).

Anyway, i'll report on the RB-048 coating as soon as I've completed it.

These are the Anthem ARC charts of the Statclear coating which did not work for my recoat. It has worked for many other users, so it may not be the coating. Maybe its the contact point to the copper strip.

 

[neil5m]

Ok I took apart the panels again post the Statclear coating which did not work for my rebuild. The coating has worked for many others so it may be something I did wrong. I used the SR meter on the panel and the coating shows largely 10^8, but in some areas 10^10. The copper strip edge had a green powder on it in areas which I guess is the coating burning off along the copper strip. I've since recoated using the RB-048 and this time used copper tape with conductive adhesive. I've also applied the coating twice on the copper strip to make sure it does not burn off.

Positives of RB-048: It was very easy to work with, has a acetone like smell and dries quickly. I applied it with a sponge. I've been using it for the last two weeks now and it sounds very good, a bit high on the upper mids, but overall very good. I'll attach a freq chart from my Anthem ARC later to this thread.

Negatives: It is sharply affected by humidity. The highs literally disappear until I have kept the AC on for at least 10 mins. After that is sounds superb. Humidity here in HK is high and is an ML-killer.

Let see how long this coating lasts!

These are the Anthem ARC freq response charts one day post the recoat. They were taken with the A/C on. Seems pretty good! I'll do another one next week and compare.

 

[Tosh]

Watching your updates with interest, Neil!

 

[JohanNap]

ME2!

ML should name their next speakers after you because of all the effort you put in yours.

 

[neil5m]

ME2!

ML should name their next speakers after you because of all the effort you put in yours.

I wish I could know and understand even a fraction of what the senior members on this group and others such as diyaudio etc. know. Its their sharing of knowledge and responses which keeps the passion of the groups members alive!

 

[headdead]

Neil
Thanks for taking the effort to share your learnings.
How is the Statclear holding up, and have you had any luck with the metallicised mylar?

 

[neil5m]

Neil
Thanks for taking the effort to share your learnings.
How is the Statclear holding up, and have you had any luck with the metallicised mylar?

Hi headdead, the Statclear did not make it. Lasted barely a week! I used a coating called RB048 from HZNano. It’s performed well since June. Is affected by humidity, but with the AC on sounds great!

 

[jacek-k-wawa]

Hi,

How this new coating is doing?
My Lycron coating died after around 1 year and I am looking for a new ideas...

 

[neil5m]

Hi,

How this new coating is doing?
My Lycron coating died after around 1 year and I am looking for a new ideas...

Hi Jacek, sorry missed your message.

The coating I used is doing well! Performs best in low humidity environments (with the A/C on).
Jos Wouters, the Quad-man, did a basic test on the coating RB-048 I used for my ML Clarity model (bias voltage of 2.5kHz).
He tested it upto 4kV bias, the SPL is good with 90db at 3kV and 93db at 4kV bias voltage.
The distortion was not low, but acceptable.
There was little to no charge migration.
The coating charged almost instantly which was positive.
Best used at lower bias voltage.
He said the frequency curve showed good linearity with no bumps or dips in the 20Hz to 20kHz.
It had to be applied quickly to the membrane (aggressive solvent - acetone based) and when dry, did not add mass to the diaphragm which was positive.

So overall a good coating. I bought it from Huzheng Nanotech in China. Shanghai Huzheng Nanotechnology Co., Ltd.

Neil

 

[jacek-k-wawa]

Thanks Neil, that is a good news!
So maybe next time (if I will have to do this again) I will consider this coating. As of now I have a very positive effects with MJ Dijkstra coating - very stable 10e9 and my MLs sound again like a charm!

 

[neil5m]

Thanks Neil, that is a good news!
So maybe next time (if I will have to do this again) I will consider this coating. As of now I have a very positive effects with MJ Dijkstra coating - very stable 10e9 and my MLs sound again like a charm!

I really wanted to try MJ’s coating. Wrote to him but never heard back from him.