lay the window screen down onto the eggcrate and then at every cross in the eggcrate use your hot soldering iron to force the screen into the plastic. Works like a charm and is easy but labor intensive.
Where can i source very thin heat shrinkable mylar and an HV bias supply? Will that aussie site ship to the US? That 3.5 micron mylar looks tempting.
I built my ESLs so long ago i have forgotten where that info is.
Thanks
Where can i source very thin heat shrinkable mylar and an HV bias supply? Will that aussie site ship to the US? That 3.5 micron mylar looks tempting.
I built my ESLs so long ago i have forgotten where that info is.
Thanks
Hi,
sorry to disillusionize a bit, but You won´t be able to build a very good ESL panel just with material You get at the grocery store
At least not in German DIY-Stores -and we Germans know DIY because we spend a lot of our lifetime at those places
It is quite easy to get the material for wire stators. PVC coated wire, plastics for spacers and frames, Aluminium bars for frame construction, glues, wood for mounting frames, paints, silicone, screws and nails and some more interesting things, but You won´t find a good diaphragm material and it will be hard to find good material for other kinds of stators too. Since Wire stators of the kind of Audiostatics are very cheap from a viewpoint of costs, I´d recommend to build a smaller wire stator ESl first.
jauu
Calvin
sorry to disillusionize a bit, but You won´t be able to build a very good ESL panel just with material You get at the grocery store
At least not in German DIY-Stores -and we Germans know DIY because we spend a lot of our lifetime at those places It is quite easy to get the material for wire stators. PVC coated wire, plastics for spacers and frames, Aluminium bars for frame construction, glues, wood for mounting frames, paints, silicone, screws and nails and some more interesting things, but You won´t find a good diaphragm material and it will be hard to find good material for other kinds of stators too. Since Wire stators of the kind of Audiostatics are very cheap from a viewpoint of costs, I´d recommend to build a smaller wire stator ESl first.
jauu
Calvin
Hi Calvin,
I agree that we can't have everything from the local shops but no harm to at least a try at it ,
Looks like wire stator is the way to go if we insist on local hardware stores... and still get away with quality ESL build.
I had made an order for some the 6uf mylar film through mail.
If we go for the wire stator, what size do you recommand as "small" monitor? and still with ego boosting result?
Cheers
KenC
I agree that we can't have everything from the local shops but no harm to at least a try at it
, Looks like wire stator is the way to go if we insist on local hardware stores... and still get away with quality ESL build.
I had made an order for some the 6uf mylar film through mail.
If we go for the wire stator, what size do you recommand as "small" monitor? and still with ego boosting result?
Cheers
KenC
Hi,
since You have to partner the panel with a bass, I´d choose the width of the panel roghly the same as the bass. The height is Your choice, depending on what You want to reach, but I´d suggest a panel with a ratio W/H of 1/4 or more. A panel of lets say 20x100cm will work from ~200Hz on and ensures enough dynamic headroom. With smaller panels the lower crossover freq rises. I would use a panel with just 10cm width not below 1kHz.
jauu
Calvin
since You have to partner the panel with a bass, I´d choose the width of the panel roghly the same as the bass. The height is Your choice, depending on what You want to reach, but I´d suggest a panel with a ratio W/H of 1/4 or more. A panel of lets say 20x100cm will work from ~200Hz on and ensures enough dynamic headroom. With smaller panels the lower crossover freq rises. I would use a panel with just 10cm width not below 1kHz.
jauu
Calvin
Hi calvin, guys,
Thanks for the suggestion. 200mmx1000m @ 200hz looks managable.
I got the impression that we can avoid lots of hassle if we keep the crossover point outside of congested frequency (i.e. within 100~150hz, below which the low freq starts to become non-directional,..etc etc...)... many speakers gurus recommand that, what is your view.
Does it mean that if I wish to increase the efficiency, I can parallel more then two panel of the same size with the same transformer? 200mm x 1m is about the right size to pair or quadra up in reasonable space...
Another question, has there been many "true" single fullrange ESL working successfully from 60hz to 30khz?? I mean can they play matallica type of music??? or what type of music can be played???
Cheers
Thanks for the suggestion. 200mmx1000m @ 200hz looks managable.
I got the impression that we can avoid lots of hassle if we keep the crossover point outside of congested frequency (i.e. within 100~150hz, below which the low freq starts to become non-directional,..etc etc...)... many speakers gurus recommand that, what is your view.
Does it mean that if I wish to increase the efficiency, I can parallel more then two panel of the same size with the same transformer? 200mm x 1m is about the right size to pair or quadra up in reasonable space...
Another question, has there been many "true" single fullrange ESL working successfully from 60hz to 30khz?? I mean can they play matallica type of music??? or what type of music can be played???
Cheers
Hi,
You might use the panel down to its ground resonance. Something ML has done. The pros are:
- easy crossover design -just a high Q-second order Highpass
- high output and
- largest possible bandwidth
- low crossover point acoustically and much higher electrically!
- use of highest mechanical tension -> stability and efficiency
The cons:
- to my experience -and I´m not alone- the high Q of the resonance (slow decay) is sonically detectable like kind of a ´footprint´
- the distortions are quite high.
- You have to control the mechanical stretching of the diaphragm quite carefully for low tolerances
The pic shows the results with my panel (ML Sequel size) and a comparison to an original ML Prodigy panel
Even though You get close to perfection measurement results it sounds better when the panel is not used down to its ground resonance. Now I use a filter that cuts off @350Hz acoustically.
You can increase efficiency by paralleling panels, Yes, But(!) the impedance curve drops and might reach very low killer levels.
Too the bandwidth of the Trannie-Panel combination sinks. You might not reach 20kHz any more.
If there are series resistances to correct for the freq-response in the HF-region the freq-response will drop even more.
I´d prefer to build a single panel rather than paralleling several smaller ones.
And Your last question: There are a few...and No!
For high SPL purposes build a Hybrid! Much better much easier and more compact!
jauu
Calvin
You might use the panel down to its ground resonance. Something ML has done. The pros are:
- easy crossover design -just a high Q-second order Highpass
- high output and
- largest possible bandwidth
- low crossover point acoustically and much higher electrically!
- use of highest mechanical tension -> stability and efficiency
The cons:
- to my experience -and I´m not alone- the high Q of the resonance (slow decay) is sonically detectable like kind of a ´footprint´
- the distortions are quite high.
- You have to control the mechanical stretching of the diaphragm quite carefully for low tolerances
The pic shows the results with my panel (ML Sequel size) and a comparison to an original ML Prodigy panel
An externally hosted image should be here but it was not working when we last tested it.
Even though You get close to perfection measurement results it sounds better when the panel is not used down to its ground resonance. Now I use a filter that cuts off @350Hz acoustically.
You can increase efficiency by paralleling panels, Yes, But(!) the impedance curve drops and might reach very low killer levels.
Too the bandwidth of the Trannie-Panel combination sinks. You might not reach 20kHz any more.
If there are series resistances to correct for the freq-response in the HF-region the freq-response will drop even more.
I´d prefer to build a single panel rather than paralleling several smaller ones.
And Your last question: There are a few...and No!
For high SPL purposes build a Hybrid! Much better much easier and more compact!
jauu
Calvin
Calvin,
I have to chew on what you had just said... as I am very new to this
Do you mean that 200~250mm x >1000mm panel, (Taller the better) @200~300hz is about as far as we can ask for with (compromised) good results and without excessive complications?
BUT I still have to limit the size of the panel within the dimension of "bicycle tyre tube stretching table". Or is there other simple stretcher that I can use?
And I'll just have to increase the tension and bias oltage to raise the SPL.
This may sound stupid but I'll ask anyway... Can we series some panel without ill effects? Since capacitance reduced when connected in series...?
AND do we still need to measure the tension of the diapharm?
Cheers
I have to chew on what you had just said... as I am very new to this
Do you mean that 200~250mm x >1000mm panel, (Taller the better) @200~300hz is about as far as we can ask for with (compromised) good results and without excessive complications?
BUT I still have to limit the size of the panel within the dimension of "bicycle tyre tube stretching table". Or is there other simple stretcher that I can use?
And I'll just have to increase the tension and bias oltage to raise the SPL.
This may sound stupid but I'll ask anyway... Can we series some panel without ill effects? Since capacitance reduced when connected in series...?
AND do we still need to measure the tension of the diapharm?
Cheers
Hi,
the prime goal in ESL construction is efficiency.
To get high efficiency You can:
- build big panels
- use smallest stator/diaphragm distances (d/s) possible
- use the highest possible voltages
- use high mechanical tension --> high ground resonance --> high dynamic stability
A d/s of ~1mm is still practical to handle and allows for frequencies down to ~200Hz. With this distance the diaphragm should be supported every 70-100mm to not to be drawn into the stators.
Stretching as hard as possible, You can get ground resonances from ~150Hz with a 3µm film to 250Hz with a 12µm film. Stretching hard raises the stability treshold and the efficiency significantely. Having the crossover not lower than one octave above Fs means a crossover point between 300 to 500Hz. When You measure the distortion You will see that they rise -rather shoot up- below 300Hz anyway. Additionally installing the panel in an open baffle You have to account for phase cancellation. So 300Hz is a good starting point for a panel (150Hz Fs) of handeable size. You can still use a passive crossover to equalize the phase cancellation.
One of the biggest mistakes of ESL-Noobs is, that they try to get down in frequency range as low as possible.
But You loose on nearly every important parameter in doing this!
You don´t necessarily need to tension mechanically. You can use heat treatment very well, but You will have to support the diaphragm with spacers closer apart than with high mechanical tension.
You can upsize the tyre stretcher by cutting the tyres and gluing together as many as You need.
Connecting ESLs in series....I have to admit that I never had that idea!
A symmetrical ESL could be considered as two series connected capacitors.
The problem is that the driving signal voltages for each panel would be halved, so efficiency wouldn´t be raised as with parallel connection. Since the capacity of this arrangement is halved too, the impedance the amp sees would be raised. While this could be desirable in the HF-range the impedance of the single panel/tranny is quite high (and doesn´t give the anp any stability problem) in the mid-band. A positive effect could be a rise in the upper bandwidth limit. But You need a higher transformation factor for the needed higher signal voltages which will impose the state of affairs again.
jauu
Calvin
the prime goal in ESL construction is efficiency.
To get high efficiency You can:
- build big panels
- use smallest stator/diaphragm distances (d/s) possible
- use the highest possible voltages
- use high mechanical tension --> high ground resonance --> high dynamic stability
A d/s of ~1mm is still practical to handle and allows for frequencies down to ~200Hz. With this distance the diaphragm should be supported every 70-100mm to not to be drawn into the stators.
Stretching as hard as possible, You can get ground resonances from ~150Hz with a 3µm film to 250Hz with a 12µm film. Stretching hard raises the stability treshold and the efficiency significantely. Having the crossover not lower than one octave above Fs means a crossover point between 300 to 500Hz. When You measure the distortion You will see that they rise -rather shoot up- below 300Hz anyway. Additionally installing the panel in an open baffle You have to account for phase cancellation. So 300Hz is a good starting point for a panel (150Hz Fs) of handeable size. You can still use a passive crossover to equalize the phase cancellation.
One of the biggest mistakes of ESL-Noobs is, that they try to get down in frequency range as low as possible.
But You loose on nearly every important parameter in doing this!
You don´t necessarily need to tension mechanically. You can use heat treatment very well, but You will have to support the diaphragm with spacers closer apart than with high mechanical tension.
You can upsize the tyre stretcher by cutting the tyres and gluing together as many as You need.
Connecting ESLs in series....I have to admit that I never had that idea!
A symmetrical ESL could be considered as two series connected capacitors.The problem is that the driving signal voltages for each panel would be halved, so efficiency wouldn´t be raised as with parallel connection. Since the capacity of this arrangement is halved too, the impedance the amp sees would be raised. While this could be desirable in the HF-range the impedance of the single panel/tranny is quite high (and doesn´t give the anp any stability problem) in the mid-band. A positive effect could be a rise in the upper bandwidth limit. But You need a higher transformation factor for the needed higher signal voltages which will impose the state of affairs again.
jauu
Calvin
Hi Calvin,
Thanks for the in-depth, More questions
Do you mean support by dividing the panel by strips of 1mm thk insulators of 70~100mm apart laid vertically on both sides of the diapharm? or using "dot" double-sided tape (or "dot" insulators) spread in random at spacing of 70~100mm from each double-sided tape point?
I read from other threads that tension is limited when heat stretch, mechanical cna stretch harder but film will sag over time... can we mechanically stretch the film then heat shrink the film and get the advantage of higher tension and no sagging in the future?
The series connection will have to wait until I build a high output voltage swing power amp before I can try em on...
Why didn't I think of tha
Cheers
Thanks for the in-depth, More questions
Do you mean support by dividing the panel by strips of 1mm thk insulators of 70~100mm apart laid vertically on both sides of the diapharm? or using "dot" double-sided tape (or "dot" insulators) spread in random at spacing of 70~100mm from each double-sided tape point?
I read from other threads that tension is limited when heat stretch, mechanical cna stretch harder but film will sag over time... can we mechanically stretch the film then heat shrink the film and get the advantage of higher tension and no sagging in the future?
The series connection will have to wait until I build a high output voltage swing power amp before I can try em on...
Why didn't I think of tha
Cheers
Hi,
the supporting points or strips can be made from tape, foam rubber, spacer material or silicone. The last beeing probabely the best because of easy handling and the adhesive and hygrophobic properties.
since this panel is curved You need horizontal supporting spacers
here a flat panel with foam rubber
You can get the highest tension by mechanical stretching. Heat treatment allows for much lower tension, but You might position the supporter points a bit closer to each other instead.
With curved panels there´s only the possibility of mechanical stretching, while flat panels allow both methods. Heat treatment is easy and gives very constant and equal tension and You don´t need to break in the panel.
For the first tries I´d recommend a flat panel with lots of silicon dots or foam rubber placed relatively close (to give a 1:70 ratio) and heat treat the diaphragm.
Heat treatment always means that the film tensions to a specific degree. If it was too lose it will tighten, if it was tensioned to hard it will lose a bit. So in practise I´d tension just a little bit by hand to get all the wrinkles out of the film, glue the stator onto the film and heat treat the thing after drying. Then place it with the film side down on a flat and clean peace of glass and press some silicone dots between stator and film. After drying You can finish the stators and build them together.
jauu
Calvin
the supporting points or strips can be made from tape, foam rubber, spacer material or silicone. The last beeing probabely the best because of easy handling and the adhesive and hygrophobic properties.
An externally hosted image should be here but it was not working when we last tested it.
since this panel is curved You need horizontal supporting spacers
An externally hosted image should be here but it was not working when we last tested it.
here a flat panel with foam rubber
You can get the highest tension by mechanical stretching. Heat treatment allows for much lower tension, but You might position the supporter points a bit closer to each other instead.
With curved panels there´s only the possibility of mechanical stretching, while flat panels allow both methods. Heat treatment is easy and gives very constant and equal tension and You don´t need to break in the panel.
For the first tries I´d recommend a flat panel with lots of silicon dots or foam rubber placed relatively close (to give a 1:70 ratio) and heat treat the diaphragm.
Heat treatment always means that the film tensions to a specific degree. If it was too lose it will tighten, if it was tensioned to hard it will lose a bit. So in practise I´d tension just a little bit by hand to get all the wrinkles out of the film, glue the stator onto the film and heat treat the thing after drying. Then place it with the film side down on a flat and clean peace of glass and press some silicone dots between stator and film. After drying You can finish the stators and build them together.
jauu
Calvin
Hi Calvin,
Thanks for the pix, now I understand exactly how.
So heat shrink the film, 1mm gap between stator and diapharm is good for high efficiency from 200~300hz up? what sort of Bias voltage are we looking? and any indiction of SPL efficiency guild?
BTW, the curve stator is pre-rolled; the diapharm follows the foam contour which follows the stator contour?
A friend found a perforated shop, I think this is good news. I hope there are sufficient veriety to choose from. While we are at it, what spec of perforated plate should I be looking for? i.e. material, %open, thiskness, hole size, holes arrangement pattern? There are too many specs mentioned in too many articles which I'd read, could you please point me the right direction?
Cheer
Thanks for the pix, now I understand exactly how.
So heat shrink the film, 1mm gap between stator and diapharm is good for high efficiency from 200~300hz up? what sort of Bias voltage are we looking? and any indiction of SPL efficiency guild?
BTW, the curve stator is pre-rolled; the diapharm follows the foam contour which follows the stator contour?
A friend found a perforated shop, I think this is good news. I hope there are sufficient veriety to choose from. While we are at it, what spec of perforated plate should I be looking for? i.e. material, %open, thiskness, hole size, holes arrangement pattern? There are too many specs mentioned in too many articles which I'd read, could you please point me the right direction?
Cheer
Hi,
I used standard HV 3/4 sheets. Mans 3mm diameter spaced 4mm apart. The sheet´s thickness should be 1mm or less.
Before coating the sheets were curved.
Looks like this
after fluidized bed coating
and after top coating
Since I didn´t electropolish the sheets a thicker insulation was necessary. The advantage is, that the holes have nicely rounded ´walls´, which prevents bandwidth limitation and the thickness is such that I can touch both stators at full loudness without getting shocked or even worse.
Next step was to glue the spacers on. While I used 1.0mm to the front, the back stator got 1.1mm thick spacers. The difference in spacer thickness is to cope for the always present bowing of the diaphragm.
After that the diaphragm is mounted in the stretching frame, stretched to a very high value of mechanical tension and glued onto the back stator.
jauu
Calvin
I used standard HV 3/4 sheets. Mans 3mm diameter spaced 4mm apart. The sheet´s thickness should be 1mm or less.
Before coating the sheets were curved.
Looks like this
An externally hosted image should be here but it was not working when we last tested it.
after fluidized bed coating
An externally hosted image should be here but it was not working when we last tested it.
and after top coating
An externally hosted image should be here but it was not working when we last tested it.
Since I didn´t electropolish the sheets a thicker insulation was necessary. The advantage is, that the holes have nicely rounded ´walls´, which prevents bandwidth limitation and the thickness is such that I can touch both stators at full loudness without getting shocked or even worse.
Next step was to glue the spacers on. While I used 1.0mm to the front, the back stator got 1.1mm thick spacers. The difference in spacer thickness is to cope for the always present bowing of the diaphragm.
After that the diaphragm is mounted in the stretching frame, stretched to a very high value of mechanical tension and glued onto the back stator.
jauu
Calvin
Here's a link to a panel on the cheap. There's even a movie. Get some popcorn, sit
back & relax....
Lucius
http://quadesl.com/diy_esl1.html
back & relax....
Lucius
http://quadesl.com/diy_esl1.html
Audio_idiot said:Hi Calvin,
Thanks for the pix, now I understand exactly how.
So heat shrink the film, 1mm gap between stator and diapharm is good for high efficiency from 200~300hz up? what sort of Bias voltage are we looking? and any indiction of SPL efficiency guild?
BTW, the curve stator is pre-rolled; the diapharm follows the foam contour which follows the stator contour?
A friend found a perforated shop, I think this is good news. I hope there are sufficient veriety to choose from. While we are at it, what spec of perforated plate should I be looking for? i.e. material, %open, thiskness, hole size, holes arrangement pattern? There are too many specs mentioned in too many articles which I'd read, could you please point me the right direction?
Cheer
Hi,
For 1 mm air gap , the bias voltage should not be very high.For uncoated stators , i'd recommend experimenting in the 1.5 - 2.5 kV range , while well coated stators may work with higher voltages without arcing.Too much bias voltage also tends to "stick" diapraghm to one of stators , if there is not enough tension.
RV 3-4 perforated steel is probably one of the best choices. If you are going to build a flat panel , the minimum steel sheet thickness is around 1mm.It also depends on panel dimensions.For curved panels , 0.7 mm thickness should be ok.
Regards,
Lukas.
Hi guys,
Thnks for sharing your eperience, greatly appricated.
Calvin,
What is fluidise bed coating? I wonder if i can do the coating at home as well?? and Electropolish??? I feel that coating the stator is essensial for the well being and safety of people around more then others... any additional labour/expenses for safety alway justify itself.
Bazokaz,
1.5~2.5Kv should be reasonable easy to build and use safely
Could you eleborate on the spec of the RV3-4 perforated steel plate?
Calvin, Bazokaz,
You guys mentioned curved stator one time too many to get me interested and the calvin's pix are just irresistable... I understand this is one way to "cure" the directivity characteristic of ESL, Since I am quite confident to get the stators rolled accurately after checking out with local metal fabricators, the devil in me just took over control of my rational senses with ease.... 
Could you kindly teach me how to make curve panels?
Cheers
Thnks for sharing your eperience, greatly appricated.
Calvin,
What is fluidise bed coating? I wonder if i can do the coating at home as well?? and Electropolish??? I feel that coating the stator is essensial for the well being and safety of people around more then others... any additional labour/expenses for safety alway justify itself.
Bazokaz,
1.5~2.5Kv should be reasonable easy to build and use safely
Could you eleborate on the spec of the RV3-4 perforated steel plate?
Calvin, Bazokaz,
You guys mentioned curved stator one time too many to get me interested
and the calvin's pix are just irresistable... I understand this is one way to "cure" the directivity characteristic of ESL, Since I am quite confident to get the stators rolled accurately after checking out with local metal fabricators, the devil in me just took over control of my rational senses with ease.... Could you kindly teach me how to make curve panels?Cheers
Hi,
RV3-4 specs are given before. Have a look at suppliers data too.
A standard size of sheet metal is 1.250x 2.500mm.
There is a outer rim of app 10mm that is not perforated.
I had my stator sheets cut in peaces of 1.250mm height and 250mm width, see second pic. (Btw. take care of how the cut is made, there should be no sharp edges or pins left). I have a unperforated part at the top and bottom of my sheets, so there´s a part where the glue for the spacers finds anough surface to hold on to.
Curving the panel is easy...just tell Your metal worker to do it for You I used 15°-20°. The reason for curving is not(!) a wider dispersion character in first place, as it is often claimed. The reason to curve is higher stability of the sheet with less resonance and rattle. It is imo the only way to manufacture stable and stiff sheet metal panels without the use of addditional bracing.
Have the sheets curved before coating.
Electropolish means a process where the sheets are put into a bath with acids. Current is led through the metal. The effect is, that sharp edges are etched away, leaving smoothly rounded holes.
The reason for this is, that field strength is high at needle like points or sharp edges. When the sheets are stamped and not drilled, they have one side with sharp edges. So these edges are very prone to flash overs. Besides higher field strength every coating is thin at such edges (data sheets sometimes state the min radius of edges for constant coating thickness). While the coating thickness may be toatally sufficient for Your use on the face sides of the sheet , it will not be at the edges! In other words. The insulation has to be thicker with sharp edges than with rounded electropolished ones.
But this process can´t be done in DIY and is quite costly.
You can coat with several polymeres and laquers. Polymeres can be applied in different ways, the best known are electrostatic spray coating and fluidized bed coating.
With the first procedure, the polymer powder is sprayed on the metal with the use of an electrostatic spray gun. After spraying the metal is heated in an oven, thereby melting the powder. This way You can reach app 200µm thickness. This isn´t thick enough for our use.
Fluidized bed means, that the powder is held in a box. When air is blown through the bottom of this box, the powder ´floats´ like a liquid.
The metal is heated up and and is dipped into the powder. The powder melts around the metal. This way You can get very even and thick coatings of up to 800µm. The big problem with perforated sheets is, that they cool down very quick...in fact too quick in most cases. The powder does not melt fully, leaving small unmelted balls of powder sticking loosely together (You can hardly see this effect, but the isolatory effect is drastically reduced)
So You have to find a coater who´s able to coat thin perforated metal sheets. Anyhow it´s very tricky to get coatings with more than ~300µm thickness.
Since The thickness of the coating wasn´t enough yet, I sprayed with an air gun several layers of an clear PU-laquer on.
If You want to coat the sheets all by Yourself You can use acrylic or PU-laqueres. I´m not a talented painter and always had problems with acrylic laqueres (they dry up quickly). The advantage is, they are water soluable. I prefer PU-laquer with which I get much smoother and better surfaces. The electrical properties of PU are excellent for ESL use either. But be prepared to coat many times thin layers till You reach the desired thickness (>500µm).
Use an air gun for coating...rolling won´t work well.
Since a professional coater provides for good reliable results (at least should he ) and the PU-laquer isn´t cheap either, I´d have first the panels coated professionally and check if there´s a need for an additional top coat later on. You not only want working results but good optics too, right?
jauu
Calvin
RV3-4 specs are given before. Have a look at suppliers data too.
A standard size of sheet metal is 1.250x 2.500mm.
There is a outer rim of app 10mm that is not perforated.
I had my stator sheets cut in peaces of 1.250mm height and 250mm width, see second pic. (Btw. take care of how the cut is made, there should be no sharp edges or pins left). I have a unperforated part at the top and bottom of my sheets, so there´s a part where the glue for the spacers finds anough surface to hold on to.
Curving the panel is easy...just tell Your metal worker to do it for You
I used 15°-20°. The reason for curving is not(!) a wider dispersion character in first place, as it is often claimed. The reason to curve is higher stability of the sheet with less resonance and rattle. It is imo the only way to manufacture stable and stiff sheet metal panels without the use of addditional bracing.Have the sheets curved before coating.
Electropolish means a process where the sheets are put into a bath with acids. Current is led through the metal. The effect is, that sharp edges are etched away, leaving smoothly rounded holes.
The reason for this is, that field strength is high at needle like points or sharp edges. When the sheets are stamped and not drilled, they have one side with sharp edges. So these edges are very prone to flash overs. Besides higher field strength every coating is thin at such edges (data sheets sometimes state the min radius of edges for constant coating thickness). While the coating thickness may be toatally sufficient for Your use on the face sides of the sheet , it will not be at the edges! In other words. The insulation has to be thicker with sharp edges than with rounded electropolished ones.
But this process can´t be done in DIY and is quite costly.
You can coat with several polymeres and laquers. Polymeres can be applied in different ways, the best known are electrostatic spray coating and fluidized bed coating.
With the first procedure, the polymer powder is sprayed on the metal with the use of an electrostatic spray gun. After spraying the metal is heated in an oven, thereby melting the powder. This way You can reach app 200µm thickness. This isn´t thick enough for our use.
Fluidized bed means, that the powder is held in a box. When air is blown through the bottom of this box, the powder ´floats´ like a liquid.
The metal is heated up and and is dipped into the powder. The powder melts around the metal. This way You can get very even and thick coatings of up to 800µm. The big problem with perforated sheets is, that they cool down very quick...in fact too quick in most cases. The powder does not melt fully, leaving small unmelted balls of powder sticking loosely together (You can hardly see this effect, but the isolatory effect is drastically reduced)
So You have to find a coater who´s able to coat thin perforated metal sheets. Anyhow it´s very tricky to get coatings with more than ~300µm thickness.
Since The thickness of the coating wasn´t enough yet, I sprayed with an air gun several layers of an clear PU-laquer on.
If You want to coat the sheets all by Yourself You can use acrylic or PU-laqueres. I´m not a talented painter and always had problems with acrylic laqueres (they dry up quickly). The advantage is, they are water soluable. I prefer PU-laquer with which I get much smoother and better surfaces. The electrical properties of PU are excellent for ESL use either. But be prepared to coat many times thin layers till You reach the desired thickness (>500µm).
Use an air gun for coating...rolling won´t work well.
Since a professional coater provides for good reliable results (at least should he
) and the PU-laquer isn´t cheap either, I´d have first the panels coated professionally and check if there´s a need for an additional top coat later on. You not only want working results but good optics too, right? jauu
Calvin
Calvin,
Thanks for your very detail explaination and instructions.
Now the specs get much more detail,
250mm x1250mm curve panel
spacer 1mm at front and 1.1mm at the back.
I will source for these now
perforated plate,
0.7~1mm thick, dia3mm 4mmc/c,
cureve 15~20degree or using 955mm ~715mm curve radius.
spacer of 1mm and 1.1mm. (ehat width are we looking at? 25mm?)
and try finding good painter for the PU coating.
This will take some time
As for the electropolishing, I read about acid etching (w/o passing electricity) of the sharp edges, are they workable?
Cheers
Thanks for your very detail explaination and instructions.
Now the specs get much more detail,
250mm x1250mm curve panel
spacer 1mm at front and 1.1mm at the back.
I will source for these now
perforated plate,
0.7~1mm thick, dia3mm 4mmc/c,
cureve 15~20degree or using 955mm ~715mm curve radius.
spacer of 1mm and 1.1mm. (ehat width are we looking at? 25mm?)
and try finding good painter for the PU coating.
This will take some time
As for the electropolishing, I read about acid etching (w/o passing electricity) of the sharp edges, are they workable?
Cheers
Calvin said:Hi,
Curving the panel is easy...just tell Your metal worker to do it for You
***
To my experience curving a panel will improve dispersion to a significant degree. I used 60 degrees (total) curvature, just like Martin Logan. What a difference with a flat panel!!!!
15 - 20 degrees (total or is it 30 - 40 total???) may be insufficient.
I doubt that the guys from ML curved their panels for increased rigidity, because their are much easier and less time consuming methods to achieve this.
Just my thougts.
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