ESL Diaphragm coating

[AndreaT]

Hello Friends,

I finally got a can of Licron Crystal a few weeks ago, but still no time to do the job.

So, before to go, do you confirm Licron Crystal to be among the best coats or not?

The last posts from Legis and Gerald made me some confusion.

Many thanks and kind regards,
Andrea

[CharlieM]

I used Licron Crystal on my current panels that I refurbished about 2 1/2 years ago, using one coat sprayed "just wet". I haven't done any measurements; just relying on my ears, but my speakers still sound great so I figure if there were a significant degradation occurring, I would have noticed it by now.

[CharlieM]

Originally Posted by CharlieM

I used Licron Crystal on my current panels that I refurbished about 2 1/2 years ago, using one coat sprayed "just wet". I haven't done any measurements; just relying on my ears, but my speakers still sound great so I figure if there were a significant degradation occurring, I would have noticed it by now.

I should also point out that my panels use a copper foil charge ring around the panel edges, rather than a single point connection to the bias supply.... not sure it matters but I suppose it could.

[geraldfryjr]

Didn't mean to sound confusing.
But I swear by it as I haven't had any issues with it so far.

Like Charlie said just make sure that you have a good wet coat when you spray it on as it will cure so thin you won't believe that it is there.
My little panels still worked flawlessly with no degradation after two years of its application.
I talked to our friend Maveric the other day and he says his panels are still kickin A$$ and he was one of the first ones to use Crystal on his very first panels after I had tried it, as it has only been about for about 3 years now.

I think the main issue has been that it is not cheap and some try to use it sparingly and/or try to make it thinner so that it is not as cloudy.
This may be possible but it will take some experimenting to get it any thinner and still have a reliable coating.
Even with a generous coat or two I can't measure the resistance with my 20 Meg ohm DVM or its exact thickness as it is only a few microns.

jer

[AndreaT]

Thank you Friends!
A can of Licron Crystal in Italy costs about 30 Euro (40 USD) plus shipping.
I will not spare it... a couple of new ML panels are priced at 1400 Euro!!!
I will spray correctly to get a good wet surface.

Many thanks again for your tips!
Regards,
Andrea

[bolserst]

Originally Posted by Legis

Right after I added ER audio's coating over the licron, all the things went back to quite normal. The neon lamp blinking speed increased to once per 7 seconds, there is clear initial fast blinking and charge rush to the membrane, output and dynamics are greater, the sound is more aggressive and involving again etc. It seems clear to me that Licron's rising resistance is the cause, and it went back to more optimal region with ER audio's coating.

Hello Legis,

When you recoated with ERaudio coating, did you replace or recoat the copper tape charge ring around your panel?
I'm wondering if perhaps you had a problem with the Licron coating being "eaten" away around the edge of the copper tape, rather than the coating as a whole.
ESL Diaphragm coating


Did you happend to measure or test the coating for conduction before and after the recoat? An easy test is to place two coins down on the coating a few inches apart and apply the HV supply with charge indicator to the coins, ground to one coin and HV output to the other. If the coating is still good you will see flashing on the charge indicator. Rapid flashing = lower resistance, slow flashing = higher resistance.

If the two coin test shows good coating conduction in the middle of the diaphragm, you can test the charge ring be placing one coin an inch or so away from the copper tape at various locations along it's length. With the HV supply connected to the charge ring, connect the coin to ground and look for flashing of the charge indicator. You would like to see rapid flashing at all positions along the copper tape.

[Legis]

Originally Posted by bolserst

Hello Legis,

When you recoated with ERaudio coating, did you replace or recoat the copper tape charge ring around your panel?
I'm wondering if perhaps you had a problem with the Licron coating being "eaten" away around the edge of the copper tape, rather than the coating as a whole.
ESL Diaphragm coating


Did you happend to measure or test the coating for conduction before and after the recoat? An easy test is to place two coins down on the coating a few inches apart and apply the HV supply with charge indicator to the coins, ground to one coin and HV output to the other. If the coating is still good you will see flashing on the charge indicator. Rapid flashing = lower resistance, slow flashing = higher resistance.

If the two coin test shows good coating conduction in the middle of the diaphragm, you can test the charge ring be placing one coin an inch or so away from the copper tape at various locations along it's length. With the HV supply connected to the charge ring, connect the coin to ground and look for flashing of the charge indicator. You would like to see rapid flashing at all positions along the copper tape.

Hi,

I did not replace the charge ring nor it's coating, just treated the radiating area of the membrane. I put triple coating over the charge ring back then. I did not measure the surface R that way, but that is a good trick to know in the future, thanks. With other indicators it's quite clear to me that the surface R got lower because of the ER audio coating.

[bolserst]

Thanks for the clarification on the recoating and charge ring.
Your experience is very puzzling/concerning as this is the first I have heard of anybody having issues with Licron coating evaporating after a few months of use. I have one pair of panels that have been in daily use for nearly 3 years with no loss of sensitivity or change in charge rate.

Did you notice any difference in the appearance of the coating?
For instance, did you notice a pattern of rings that match up with the perforations in your stators? This might indicate low level ionization from the sharp edges of the stators was attacking the coating.

[CharlieM]

Originally Posted by bolserst

...I'm wondering if perhaps you had a problem with the Licron coating being "eaten" away around the edge of the copper tape, rather than the coating as a whole.

After reading this a thought occurred to me:
I've always attached the diaphragm to one stator and the charge ring to the opposing stator and I haven't experienced any problems so far. Although this obviously provides a workable electrical contact, perhaps the contact is not so intimate as to prevent arcing between the charge ring and diaphragm coating. For the charge ring, I use adhesive backed copper foil from McMaster-Carr, which is available with either a conductive or a non-conductive adhesive backing. Now I'm thinking it might be better to use the foil with the conductive adhesive and place the charge ring on the same stator, with its conductive adhesive directly against the diaphragm coating. I'm thinking this would provide a more intimate electrical coupling, less prone to arcing... any thoughts on this?

[bolserst]

Originally Posted by CharlieM

I'm thinking it might be better to use the foil with the conductive adhesive and place the charge ring on the same stator, with its conductive adhesive directly against the diaphragm coating. I'm thinking this would provide a more intimate electrical coupling, less prone to arcing... any thoughts on this?

I always recommend using the conductive adhesive version of the copper tape stuck down on top of the the coating. It is definitely less prone to corona discharge along the edges of the tape. Try it in the dark with the top stator removed. The non-conductive tape will glow purple long before the conductive tape will.

Calvin's recommendation of a thin layer of paper soaked with conductive coating fluid layed over the copper tape out on to the coating also helps avoid the large resistance discontinuities which leads to corona forming along the tape edges.

BTW, corona discharge along the tape edges becomes more of a problem for HV bias levels above 3kV.