Hi,
Exactly. You need to gain some experience before building a final set.
It is good. While it does not provide precision tuning of bias supply voltage The schematic is simple to build and reliable. No possible interferences from switch mode operation. There is a set of definite output voltages after each multiplier stage; any of these can be used.
Please read this thread :
http://www.diyaudio.com/forums/planars-exotics/109789-esl-diaphragm-coating.html
There are a variety of formulations. Currently Licron Crystal is very popular here. Other antistatic coatings may work, also there are companies who sell the coating specifically formulated for ESLs.
Graphite is not the best material to start with. It is very difficult to apply in a layer having sufficiently high and uniform resistance. If you simply rub graphite on the resistance will be far too low causing charge migration and increased distortion. Wiping with alcohol can help but the process becomes long and difficult, and you will need some equipment to measure if resistance is uniform and high enough.
Also there is no possibility to selectively exclude areas of membrane like bolts, neither to remove the layer with solvent and re-apply again.
Lukas.
Exactly. You need to gain some experience before building a final set.
It is good. While it does not provide precision tuning of bias supply voltage The schematic is simple to build and reliable. No possible interferences from switch mode operation. There is a set of definite output voltages after each multiplier stage; any of these can be used.
Please read this thread :
http://www.diyaudio.com/forums/planars-exotics/109789-esl-diaphragm-coating.html
There are a variety of formulations. Currently Licron Crystal is very popular here. Other antistatic coatings may work, also there are companies who sell the coating specifically formulated for ESLs.
Graphite is not the best material to start with. It is very difficult to apply in a layer having sufficiently high and uniform resistance. If you simply rub graphite on the resistance will be far too low causing charge migration and increased distortion. Wiping with alcohol can help but the process becomes long and difficult, and you will need some equipment to measure if resistance is uniform and high enough.
Also there is no possibility to selectively exclude areas of membrane like bolts, neither to remove the layer with solvent and re-apply again.
Lukas.
Yes I would start of by building the Bias supply.
This will help you to get accustom to high voltages and use it to test various coatings for breakdown failure.
The biggest mistake I have seen happen is when one gets every thing glued together only to find their stator coating was inferior and failed, ruining a perfectly good piece of mylar as it is not exactly cheap in small quanities.
Here is great thread dedicated to many of the things found suitable for stator coating use,
http://www.diyaudio.com/forums/plan...ectric-coatings-fact-fiction.html#post2779101
You can vari the bias voltage by choosing different taps along the multiplier stack or you can use a chipamp to power the supply stepup tansformer as I had mentioned earlier.
This would be much easier to do then developing some some sort of switching type.
I took me a couple of months and many blown FET's to develop my circuit into a reliable one.
A chipamp makes this much easier to do.
I made my first supply from a old 340v tube amp transformer with about 12 stages (I think) and was plenty at about 5.8Kv.
Later I added more stages when I started testing coatings and stuff.
But ultimately I used less by the time I got my first panels built and running.
After I had learned more about the coatings was when I was able to build a panel that could sustain a much higher voltage.
If you can get 6v/240V transformers for the step-up transformer stage these may be a better choice.
A 240v type of winding will most likely be one complete winding rather than having two 115V windings that are Bifilar wound.
Bifilar winding's add a lot of stray capacitance to the transformer and there is an imbalance of the voltages across the whole winding when they are tied in series and could cause a breakdown failure.
But you have to be pushing them rather hard in order for these conditions to occur and work very well under normal conditions
As for the diaphragm coating I started out using graphite and this was very messy and many times was unreliable as it didn't bond to the mylar well and it would lift off and the panel would stop working.
It was almost impossible to get a consistent high resistance coating.
This was when I discovered Licron and never turned back way back in 2003 when it first came about.
Many have used other similar products such as Staticide with good results I have not tried this product yet.
There is a whole thread dedicated to diaphragm coatings as Lukas has posted.
There have been a few other substances that have been used from liquid detergents,PVA white glue,antistatic computer screen cleaners to F21 turtle wax products that have been claimed to work a well.
I have not tried any of these yet, But there is always a never ending search for a good inexpensive coating.
All of these are mentioned and discussed in the diaphragm coatings thread.
jer
This will help you to get accustom to high voltages and use it to test various coatings for breakdown failure.
The biggest mistake I have seen happen is when one gets every thing glued together only to find their stator coating was inferior and failed, ruining a perfectly good piece of mylar as it is not exactly cheap in small quanities.
Here is great thread dedicated to many of the things found suitable for stator coating use,
http://www.diyaudio.com/forums/plan...ectric-coatings-fact-fiction.html#post2779101
You can vari the bias voltage by choosing different taps along the multiplier stack or you can use a chipamp to power the supply stepup tansformer as I had mentioned earlier.
This would be much easier to do then developing some some sort of switching type.
I took me a couple of months and many blown FET's to develop my circuit into a reliable one.
A chipamp makes this much easier to do.
I made my first supply from a old 340v tube amp transformer with about 12 stages (I think) and was plenty at about 5.8Kv.
Later I added more stages when I started testing coatings and stuff.
But ultimately I used less by the time I got my first panels built and running.
After I had learned more about the coatings was when I was able to build a panel that could sustain a much higher voltage.
If you can get 6v/240V transformers for the step-up transformer stage these may be a better choice.
A 240v type of winding will most likely be one complete winding rather than having two 115V windings that are Bifilar wound.
Bifilar winding's add a lot of stray capacitance to the transformer and there is an imbalance of the voltages across the whole winding when they are tied in series and could cause a breakdown failure.
But you have to be pushing them rather hard in order for these conditions to occur and work very well under normal conditions
As for the diaphragm coating I started out using graphite and this was very messy and many times was unreliable as it didn't bond to the mylar well and it would lift off and the panel would stop working.
It was almost impossible to get a consistent high resistance coating.
This was when I discovered Licron and never turned back way back in 2003 when it first came about.
Many have used other similar products such as Staticide with good results I have not tried this product yet.
There is a whole thread dedicated to diaphragm coatings as Lukas has posted.
There have been a few other substances that have been used from liquid detergents,PVA white glue,antistatic computer screen cleaners to F21 turtle wax products that have been claimed to work a well.
I have not tried any of these yet, But there is always a never ending search for a good inexpensive coating.
All of these are mentioned and discussed in the diaphragm coatings thread.
jer
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8 oz can is quite a lot if you apply it thin.
In my case the usage is about 4-6ml/m^2 when applied with a cotton wipe, so one spray can should be enough for several tens of sq. meters. I think that's more than you are willing to build over you life
. Surely it has some storage life limitation.Note that it is important to have a very good contact between licron and copper adhesive strip which is used to supply charge.Otherwise corona can eat the coating near contact point. Apply licron before gluing copper tape and then on top where copper and mylar meets by using a small brush.
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I have had my original can of Licron since 2003 and out of the 3 or 4 small sets that I have made I have rediaphragmed them maybe 2 or 3 times as some had a set of thicker replaceable frames.
And I still have about 2/3's of that same can.
And I have a nearly full can of Crystal formula that I got back in 2010 as I have only used it a few times.
It goes a long way!!
I posted some pictures a while back of one of the original diaphragms that I made in 2003 and it still works today except for the holes that are in it now.
It never wore off even after much deliberate environmental abuse for 7 years.
I have this documented in one of the threads.
jer
And I still have about 2/3's of that same can.
And I have a nearly full can of Crystal formula that I got back in 2010 as I have only used it a few times.
It goes a long way!!
I posted some pictures a while back of one of the original diaphragms that I made in 2003 and it still works today except for the holes that are in it now.
It never wore off even after much deliberate environmental abuse for 7 years.
I have this documented in one of the threads.
jer
Right, I will definitely be using it then. A lot of people are saying they have had good results with it and if it goes as far as you said and it lasts for years, then that is proof enough for me
I have enough information I think now to gather some materials together, so hopefully later in the year I can start experimenting. I have a few other projects on I need to get done (conservatory and landscaping the garden) before I can start building any more audio gear, oh and it's always a tough one explaining to the wife why you have to keep building audio stuff! But at least she does appreciate the quality of the finished results, she can hear the difference in quality from most of the stuff I build when compared to a fairly expensive Denon AV amp and Monitor Audio speakers.
She was a little concerned about the voltages present on ESLs as we have a 12 week old baby that will soon be crawling and toddling around, but as I'm and electrical engineer by trade and explained how they work and that the current is very small, she seemed to turn to the idea.
Thanks again. I'll post some pictures when I get around to building.
I have enough information I think now to gather some materials together, so hopefully later in the year I can start experimenting. I have a few other projects on I need to get done (conservatory and landscaping the garden) before I can start building any more audio gear, oh and it's always a tough one explaining to the wife why you have to keep building audio stuff! But at least she does appreciate the quality of the finished results, she can hear the difference in quality from most of the stuff I build when compared to a fairly expensive Denon AV amp and Monitor Audio speakers.
She was a little concerned about the voltages present on ESLs as we have a 12 week old baby that will soon be crawling and toddling around, but as I'm and electrical engineer by trade and explained how they work and that the current is very small, she seemed to turn to the idea.
Thanks again. I'll post some pictures when I get around to building.
Very good, it will be great to see another successful DIY ESL build!!!
When I first got going everything I saw I would wonder to myself "Hey I wonder of that would work!! ".
I think I spent about $200 on different materials to try only to find that my first set cost less than $20 to build and lasted for nearly 9 years had I not burned them up pushing them past there limits.
Well, I still have one of the those two panels anyhow and all of the other ones I made too!
jer
When I first got going everything I saw I would wonder to myself "Hey I wonder of that would work!! ".
I think I spent about $200 on different materials to try only to find that my first set cost less than $20 to build and lasted for nearly 9 years had I not burned them up pushing them past there limits.
Well, I still have one of the those two panels anyhow and all of the other ones I made too!
jer
This is vary true...This is were most of the panels fale..An run the Copper all the way Around the panel...you get the most output out of panel this way...It can be good for 2-3 more db output...
An If you can bild the panels so you can open them...i find after 6monts...thay can lose 20% output from dust..open an clen an it like new panels agin.. Just my 5cent....Good luck
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Depending upon where you are, Humidity can sometimes be an issue when using copper for a charge ring as it corrodes very easily.
I have always used aluminum tape for my charge rings and connections to the diaphragm and never had an issue with it even after 9 years and have been beat up with road salt.
Even though I don't live in a high humidity area anymore either.
But since then I have switched to using a conductive glue made out of some white glue (Elmers), water, Graphite and a few drops of dawn dish soap to keep it from beading up as it is painted on to the frames.
This method works beautifully and will never ever corrode.
It can be applied directly upon the licron coating or just sandwiched against the coated mylar, either way as long as it is making contact it will work.
Since it is conducting HV the resistance of the material has no effect on the system.
jer
I have always used aluminum tape for my charge rings and connections to the diaphragm and never had an issue with it even after 9 years and have been beat up with road salt.
Even though I don't live in a high humidity area anymore either.
But since then I have switched to using a conductive glue made out of some white glue (Elmers), water, Graphite and a few drops of dawn dish soap to keep it from beading up as it is painted on to the frames.
This method works beautifully and will never ever corrode.
It can be applied directly upon the licron coating or just sandwiched against the coated mylar, either way as long as it is making contact it will work.
Since it is conducting HV the resistance of the material has no effect on the system.
jer
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The white PVA glue used as a binder in some DIY diaphragm coatings has an affinity for water, which I think would facilitate (and accelerate) corrosion of the copper foil charge ring. My first panels used a non-PVA coating (not Licron), and when I dismantled one after two years, I saw very little oxidation and no actual corrosion on the charge ring. My latest panels, which use Licron Crystal on the diaphragms, have been playing for three years now with no problems. Since you will be experimenting before making your full-up panels anyway, rather than placing the charge ring on the opposite stator as shown on my blog, I suggest you purchase the type copper foil that has a conductive adhesive, and then place the foil directly onto the diaphragm, adhesive side contacting the Licron coating. I think this would provide a more intimate contact less prone to coronal erosion of the Licron, and any oxidation would likely be limited to the bare opposite side of the foil. I haven't tried this myself, but I will if I ever have to rebuild my current panels.
Hi,
Just another word about safety. In no. 67 you wrote that You told Your wife about the functioning of th panel and safety due to low currents. This is true as long as there's no insulation breakdown. In case of playing music and touching a faulty stator one may get shocked. The amplifier driving the Stat may push serious amounts of power through the transformer.
The impedances on the HV side may be low enough to allow for possibly lethal high currents!
If you want an optically open system, I'd suggest to build a wire stator, especially if You have not extensive experience with coating metal sheets.
Accepting a small minor in optics and acoustics, I'd suggest to build a optically closed system in which the stator is either covered by a thick layer of acoustic foam, or shielded behind PE grounded metal sheets. I'D also cover the whole front and backside with acoustic cloth to optically hide that there are holes in the metal sheet where the enterprising baby may poke through.
We want the baby to grow up and enjoy Barbecues not becoming Babycue.
Jauu
Calvin
Just another word about safety. In no. 67 you wrote that You told Your wife about the functioning of th panel and safety due to low currents. This is true as long as there's no insulation breakdown. In case of playing music and touching a faulty stator one may get shocked. The amplifier driving the Stat may push serious amounts of power through the transformer.
The impedances on the HV side may be low enough to allow for possibly lethal high currents!
If you want an optically open system, I'd suggest to build a wire stator, especially if You have not extensive experience with coating metal sheets.
Accepting a small minor in optics and acoustics, I'd suggest to build a optically closed system in which the stator is either covered by a thick layer of acoustic foam, or shielded behind PE grounded metal sheets. I'D also cover the whole front and backside with acoustic cloth to optically hide that there are holes in the metal sheet where the enterprising baby may poke through.
We want the baby to grow up and enjoy Barbecues not becoming Babycue.
Jauu
Calvin
Yes, this is very true and since this are basically huge capacitors one should never ever touch either/or both stators at the same time while they are playing becuase they will/do conduct when AC voltages are present.
Especially at the higher frequency's.
As for an example a typical panel of 12" X 48" with a D/S .0625" will present a capacitance of at least .001uf with reactance of about 8000 ohms at 20Khz.
Let us consider an ideal transformer at 1:100 step up ratio and with a 10Vrms input we get 1000Vrms output.
At 1000Vrms/8000 ohms =.125 amps of ac current and 1000*1000/8000=125 watts of power.
Providing your amp has the power maintain 20Vrms input to the transformer this would mean .250 amps of AC current and 500 watts of power.
At this level it would be very loud and you would be hard pressed to get close enough to the panel to even touch it.
But, if you could,DON'T DO IT !!!!!
When I burned up my last wire mesh panel I had an amp capable of maintaining this type of voltage and more at a full 625 watts at the least.
I was also using a 1:256 setup up ratio and when the coating failed it formed a solid continuous arc.
The current that was flowing through the now short circuited panel was high enough to turn the aluminium wire bright orange and cherry red in about a .75" diameter spot.
I left it to run like this for about a good minute before I decided shut it down.
It is because of these much higher currents at high frequency's is when you will find your weakest points in the stator coating.
Remember, Your Impedance gets lower as the frequency goes up!
And because there is more current available to over come the resistance of the coating and heat it up.
Simple Ohms Law here and nothing special.
Yes, I have been nailed by the the voltages coming out of the transformer using only a 100 watt amp and it is not for the ill fated.
They do pack a serious Walup!!!!
Just the same as you should never mess around with the speaker leads coming out of a 150watt and bigger amplifier while it is playing.
There is a potential of over 100V p-p coming out of the thing!!!
The last time I got nailed was with the full 13.6KV output of my HV supply and I can a test to you that I wouldn't be sitting here telling you this story had I not kept one hand in my pocket while I was working with them at such levels.
I'm very serious about this and I am not joking here!!!
Although I am working with voltages 2 to 3 times more that what is necessary to make them work, THE SAME RULES APPLY!!!
FWIW
jer
Especially at the higher frequency's.
As for an example a typical panel of 12" X 48" with a D/S .0625" will present a capacitance of at least .001uf with reactance of about 8000 ohms at 20Khz.
Let us consider an ideal transformer at 1:100 step up ratio and with a 10Vrms input we get 1000Vrms output.
At 1000Vrms/8000 ohms =.125 amps of ac current and 1000*1000/8000=125 watts of power.
Providing your amp has the power maintain 20Vrms input to the transformer this would mean .250 amps of AC current and 500 watts of power.
At this level it would be very loud and you would be hard pressed to get close enough to the panel to even touch it.
But, if you could,DON'T DO IT !!!!!
When I burned up my last wire mesh panel I had an amp capable of maintaining this type of voltage and more at a full 625 watts at the least.
I was also using a 1:256 setup up ratio and when the coating failed it formed a solid continuous arc.
The current that was flowing through the now short circuited panel was high enough to turn the aluminium wire bright orange and cherry red in about a .75" diameter spot.
I left it to run like this for about a good minute before I decided shut it down.
It is because of these much higher currents at high frequency's is when you will find your weakest points in the stator coating.
Remember, Your Impedance gets lower as the frequency goes up!
And because there is more current available to over come the resistance of the coating and heat it up.
Simple Ohms Law here and nothing special.
Yes, I have been nailed by the the voltages coming out of the transformer using only a 100 watt amp and it is not for the ill fated.
They do pack a serious Walup!!!!
Just the same as you should never mess around with the speaker leads coming out of a 150watt and bigger amplifier while it is playing.
There is a potential of over 100V p-p coming out of the thing!!!
The last time I got nailed was with the full 13.6KV output of my HV supply and I can a test to you that I wouldn't be sitting here telling you this story had I not kept one hand in my pocket while I was working with them at such levels.
I'm very serious about this and I am not joking here!!!
Although I am working with voltages 2 to 3 times more that what is necessary to make them work, THE SAME RULES APPLY!!!
FWIW
jer
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Hi,
One could also build stator from three metal sheets(1-2-3), two of them(1-2) used for driving the membrane and one placed on the back as a shield.
Front and back sheets are connected together and grounded.This way the system is quite safe to touch from both sides. A step further is to add an additional diaphragm between 2-3 and use two bias supplies with reverse polarities(two-membrane sandwich).
I fully agree about wire stators for safety reasons. If the wire is of good quality the insulation is quite robust and will need a sharp knife with some force to be damaged. One of my old panels has had received impacts that caused wires to bend considerably and elongate, but the insulation was intact.
One can cover wire stators with a thin, partially transparent synthetic cloth.
1) Adds up in dampening the fundamental resonance
2) No need to make construction optimized for optics
3) Acts like a dust cover
Lukas.
Just to be clear, the potentially dangerous high voltages Calvin mentioned are present on the secondary side of the step-up transformer. The current is limited only be the current capability of the amplifier and the impedance of the transformer windings or any impedance put in series with the transformer primary or secondary.
It has nothing to do with the ESL panel being a large capacitor. The potential danger from the voltage on the secondary is the same no matter what the size of the ESL or even if the stators are hooked up. Granted, stators are easily accessed by anybody in the household where as the secondary connections would hopefully be safely covered in a case.
Another take-away from this is that no matter how well insulated your stators, always be careful poking around your ESL step-up transformer wiring if an amplifier is hooked up and music is playing.
Yes, I meant physically huge meaning that you can lay your hand on them and this is enough surface area for the AC high voltage to conduct to your hand and through your body if you were to grab the other side while they are playing.
I know this is true because Mavric told me he did this once, After I told him not too!!!! Ahhh,ha,ha,ha
The times I got nailed was from accidently touching a bare wire connection.
Also a wire that had a rather thin insulation covering on it.
And in the one case coming too close to the bias feed as it was charged to 12Kv.
Sorry for the confusion!!
jer
I know this is true because Mavric told me he did this once, After I told him not too!!!! Ahhh,ha,ha,ha
The times I got nailed was from accidently touching a bare wire connection.
Also a wire that had a rather thin insulation covering on it.
And in the one case coming too close to the bias feed as it was charged to 12Kv.
Sorry for the confusion!!
jer
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I get your point, and I will definitely be careful when building and experimenting. I am aware of high voltages as I am a SAP (Senior Authorised Person) on our 11KV networks at our larger sites at work. These systems are not to be messed with, 11KV ring main systems with the capability of carrying 200-300 amps!
I like the idea of using extra mesh on the front and back which are grounded, very good idea. I suppose mesh could be used with a much larger open area so as not to disturb the response too much.
I like the idea of using extra mesh on the front and back which are grounded, very good idea. I suppose mesh could be used with a much larger open area so as not to disturb the response too much.
Sorry, I understood from checking out your other projects that you are not a newcomer to electronics.
Clarification was mainly for others who might read this thread at a later date and don't have your background.
This is an excellent solution.
Attached pic shows high % open area mesh used as grounded safety shields on some models of King Sound ESLs.
Concerning HV bias contact corrsion:
Back when I was building stacks of test panels and Licron didn't exist, I come up with the following solution. I applied coating to the diaphragm leaving a 1/8" border inside the spacers. Copper tape was run around the panel in the middle of the spacers. Patches of Dag graphite were painted on to join the copper contact strip and coating.
This minimized leakage currents across spacers in humid conditions and avoided any possibility of corrosion. One of my favorite coatings at the time was Ivory dishwashing liquid soap thinned 1:3 with water and air-brushed on. Even that has shown no corrosion tendencies with the graphite after 15+ years.
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