I understand that the bias voltage causes the diaphragm to be displaced from the central "neutral" position but I've not noticed a difference between the tone generated by tapping on an ESL panel with the bias voltage on versus tapping on the same panel with the bias voltage off. I have to admit I haven't done a careful study, so I could end up eating crow, but it would come as a surprise to me if the change in frequency was significant. I_F, have you done a careful enough experiment to be able to report what the typical magnitude of change is? Are we talking about a 1 Hz change in a 100 Hz resonance or something larger?
Hi,
its good to apply the 1:70 to 1:100 rule. This means that the diaphragm should be supported at points where the shortest distance measured over the diaphragm becomes the 70 to 100 times the d/s. With a d/s of 0.055" the distance between two spacer elements should be 0.055"x70 = 3.85" to 0.55"x100 = 5.5". Having a width of 4.5" You won´t need any horizontal spacer at all. With these dimensions heat shrinking the diaphragm should give just under 100Hz of resonance. So in this caseI´d rather use the heat gun for ease of construction (the pic shows the nearfield response of a small panel with app. 1.5mm d/s and 90x750mm diaphragm. I use 3.5µm film heat shrunk i and coated it with a highly transparent solution I made myself).
When highly resistive coating is used the resistor for the high voltage cascade doesn´t need to be as big as Bill quoted. In fact You wouldn´t need it at all for these kinds of coatings. But its quite useful for experimentation and safety reasons to limit the maximum current in case of touching something while building or leakage. But since the voltage drop over the resistance reduces the bias on the diaphragm it should be kept as small as needed for safe working. 10 to 20meg are sufficient. With low resistance coatings higher resistance values will be needed (as this resistor smooths out the ripple voltage of the cascade high ohmic values filter stronger This might be of interest especially when the high voltage is taken from the ´half-points of the cascade´where a high ripple exists.).
jauu
Calvin
its good to apply the 1:70 to 1:100 rule. This means that the diaphragm should be supported at points where the shortest distance measured over the diaphragm becomes the 70 to 100 times the d/s. With a d/s of 0.055" the distance between two spacer elements should be 0.055"x70 = 3.85" to 0.55"x100 = 5.5". Having a width of 4.5" You won´t need any horizontal spacer at all. With these dimensions heat shrinking the diaphragm should give just under 100Hz of resonance. So in this caseI´d rather use the heat gun for ease of construction (the pic shows the nearfield response of a small panel with app. 1.5mm d/s and 90x750mm diaphragm. I use 3.5µm film heat shrunk i and coated it with a highly transparent solution I made myself).
When highly resistive coating is used the resistor for the high voltage cascade doesn´t need to be as big as Bill quoted. In fact You wouldn´t need it at all for these kinds of coatings. But its quite useful for experimentation and safety reasons to limit the maximum current in case of touching something while building or leakage. But since the voltage drop over the resistance reduces the bias on the diaphragm it should be kept as small as needed for safe working. 10 to 20meg are sufficient. With low resistance coatings higher resistance values will be needed (as this resistor smooths out the ripple voltage of the cascade high ohmic values filter stronger This might be of interest especially when the high voltage is taken from the ´half-points of the cascade´where a high ripple exists.).
jauu
Calvin
Hi,
I have found one type of shoe polish to work well for coating. I apply it with a parlon. Then i take a fresh piece of parlon , moist it and remove excess of polish.
The surface gets slightly whitish , and shoe polish actually dries out well and sticks to mylar quite good.It is much easier to work than graphite , and seems to give higher resistance (depending on amount of polish applied).
I have no idea about long-term reliability.
Best regards.
Lukas.
I have found one type of shoe polish to work well for coating. I apply it with a parlon. Then i take a fresh piece of parlon , moist it and remove excess of polish.
The surface gets slightly whitish , and shoe polish actually dries out well and sticks to mylar quite good.It is much easier to work than graphite , and seems to give higher resistance (depending on amount of polish applied).
I have no idea about long-term reliability.
Best regards.
Lukas.
Lukas, what lead you to try shoe polish? I'm not familiar with a parlon. Can you describe it?
I tried a couple of off-the-shelf household items in a search for an easy to apply, inexpensive coating. Anti-static spray meant to be used on clothes gave a suitably high resistance, was easy to apply, but didn't seem to dry enough to be permanent. Rain-X, made for car windshields was easy to apply, but had infinite resistance.
I'm going to try graphite again. Rub it in, remove the excess with alcohol, and see what happens. If it doesn't work, I'll order a can of Licron.
Here's a photo of the stretching jig v1.1.
Thanks to all for your ideas and suggestions. I think you'll see many of them used in the latest version of the jig.
The v1.0 moveable parts on the long side have been divided into three pieces and the holes they are mounted to have been slotted to allow up to 5/16" of movement while stretching. I've added some foam blocks between the moveable parts and the main frame to stabilize the moveable parts.
There's no film in the photo. When it's in place, it will be held to the moveable parts with double sided tape. The splines in v1.0 just didn't work out.
In the center of the jig is a table used to apply the graphite. The table is removeable and sitting on six 3/4" thick MDF blocks that are attached to the baseplate. It's made of 5/8" chipboard with 1/8" masonite glued to it and a top layer of white paper. It's hard to see, but there are guidelines on the paper. There's a rectangle the same size as the ESL stator, and two other rectangles, each 1/4" inside the other. The middle guideline is where I'll put masking tape on the diaphragm to end the coating. The inner guideline is in line with the inner edge of the stator as a reference.
Thanks to all for your ideas and suggestions. I think you'll see many of them used in the latest version of the jig.
The v1.0 moveable parts on the long side have been divided into three pieces and the holes they are mounted to have been slotted to allow up to 5/16" of movement while stretching. I've added some foam blocks between the moveable parts and the main frame to stabilize the moveable parts.
There's no film in the photo. When it's in place, it will be held to the moveable parts with double sided tape. The splines in v1.0 just didn't work out.
In the center of the jig is a table used to apply the graphite. The table is removeable and sitting on six 3/4" thick MDF blocks that are attached to the baseplate. It's made of 5/8" chipboard with 1/8" masonite glued to it and a top layer of white paper. It's hard to see, but there are guidelines on the paper. There's a rectangle the same size as the ESL stator, and two other rectangles, each 1/4" inside the other. The middle guideline is where I'll put masking tape on the diaphragm to end the coating. The inner guideline is in line with the inner edge of the stator as a reference.
Attachments
Here's a photo of the v1.1 jig with the frame opened, the table removed, and the stator in place as it would be for gluing to the diaphragm. There's two hinges in the back that hold it all together.
There's no diaphragm in the picture, but it would be on top of the top section.
Shortly before I took the picture, I knocked the stick I was using to hold it open and the top hit me on the head.
I'm lucky I made contact with the frame and not the threaded rods sticking out of the frame.
There's no diaphragm in the picture, but it would be on top of the top section.
Shortly before I took the picture, I knocked the stick I was using to hold it open and the top hit me on the head.
I'm lucky I made contact with the frame and not the threaded rods sticking out of the frame.Attachments
BillH said:
Sorry ,
i used a wrong word. I ment foam rubber.
I have found that with graphite it is hard to archieve uniform coating and the resistance is too low. Also , much of messy work. That's why i tried other coatings. I liked liquid soap much better than graphite , though some say that it "evaporates" over longer periods of time.
Regards,
Lukas.
Hi,
my small contribution to the subject of stretching jigs:
Instead of wood I use pvc tubes for the moving inner parts to which the mylar must be attached. This solves the problem of obtaining a good strong bond between the jig and the mylar during stretching, which in my experiences can be troublesome with (unpainted) wood. I use small strips of double sided adhesive tape which sticks very well to both tubes and mylar. Also the rounded surface increases bonding and reduces risk of tearing.
In addition the tubes are mounted in such a way that they extend from the surface of the jig, I hope the picture clarifies.
This allows me to place the mylar on a flat surface and use some tape to lay it out flat without wrinkles (no tension applied yet). Then I place the jig on top of that, tubes facing down, "picking up" the sheet from table to jig.
For measuring tension I draw a rectangle on the untensioned mylar and carefully measure it's dimensions whlie stretching, which allows for pretty good reproducability. Because the tubes can flex a little I can evenly distribute the tension over the entire surface by adjusting the various screws.
About coating: various kinds of glue seem to work as well (dilute and apply by airbrush). Haven't tried it myself no no idea about long-term stability
Just some more ideas..
my small contribution to the subject of stretching jigs:
Instead of wood I use pvc tubes for the moving inner parts to which the mylar must be attached. This solves the problem of obtaining a good strong bond between the jig and the mylar during stretching, which in my experiences can be troublesome with (unpainted) wood. I use small strips of double sided adhesive tape which sticks very well to both tubes and mylar. Also the rounded surface increases bonding and reduces risk of tearing.
In addition the tubes are mounted in such a way that they extend from the surface of the jig, I hope the picture clarifies.
This allows me to place the mylar on a flat surface and use some tape to lay it out flat without wrinkles (no tension applied yet). Then I place the jig on top of that, tubes facing down, "picking up" the sheet from table to jig.
For measuring tension I draw a rectangle on the untensioned mylar and carefully measure it's dimensions whlie stretching, which allows for pretty good reproducability. Because the tubes can flex a little I can evenly distribute the tension over the entire surface by adjusting the various screws.
About coating: various kinds of glue seem to work as well (dilute and apply by airbrush). Haven't tried it myself no no idea about long-term stability
Just some more ideas..
Attachments
coating
Hi,
some glues work and some don´t. Even so they might look the same, smell the same and taste the same
You may have to experiment with different manufacturers.
As far as my experiences with my formula are it is stable now for several years. Just today I got my oldest panels out of the houses cellar with its damp -its a very old house with the ground beeing stamped mud- climate, open to frost and heat. I didn´t even dust them and they played instantly. I measured no loss of SPL and couldn´t see any damaged or missing area of coating -admittantly thats difficult, because its highly transparent.
The coating can be applied with a piece of foam as well as with an airbrush. The conductivity can be tailored to fit the application and the ingredients are human-friendly, water-based, not poisoneous.
I can recommend the use of glue-based coating.
jauu
Calvin
Hi,
some glues work and some don´t. Even so they might look the same, smell the same and taste the same
You may have to experiment with different manufacturers. As far as my experiences with my formula are it is stable now for several years. Just today I got my oldest panels out of the houses cellar with its damp -its a very old house with the ground beeing stamped mud- climate, open to frost and heat. I didn´t even dust them and they played instantly. I measured no loss of SPL and couldn´t see any damaged or missing area of coating -admittantly thats difficult, because its highly transparent
.The coating can be applied with a piece of foam as well as with an airbrush. The conductivity can be tailored to fit the application and the ingredients are human-friendly, water-based, not poisoneous.
I can recommend the use of glue-based coating.
jauu
Calvin
Member
Joined 2003
I spent some time this weekend working on the back panels and veneering the ESL frame.
The back panels will hold IEC power connectors and binding posts for audio in. Somehow I managed to drill and dremel the holes in one panel backwards. I'll have to redo that one.
The veneering went quite well, no mistakes so far. The walnut veneer came from a seller on Ebay. I'll have pictures after the veneer has a couple of coats of clear on it. I should have the contact cement off my fingers by then, too.
The back panels will hold IEC power connectors and binding posts for audio in. Somehow I managed to drill and dremel the holes in one panel backwards.
I'll have to redo that one.The veneering went quite well, no mistakes so far. The walnut veneer came from a seller on Ebay. I'll have pictures after the veneer has a couple of coats of clear on it. I should have the contact cement off my fingers by then, too.
Hi,
if you are looking for an appropriate coating, the most important is that its not affected by humidity.
Most DIY-coatings are based on any kinds of glues. But all glue-based-coatings are not intrinsically conductive. glue based coatings form a specific surface, which "invite" water molecules to settle on the surface, thus increasing the surface conductivity. But depending on humidity the conductivity varies significantly.
Even it might still work at low humidity, the resistance is too high to allow fully charge of the membrane.
For my knowledge there are just few coating systems avaible which are permanently intrinsic conductive:
- Nylon disolved (but very high resistance, takes weeks to fully charge !!, some people dope it with ultrafine graphite)
- Baytron (modification by TDA,distributed by sigma-aldrich)
- Carbon black (epoxy with carbon-nano-fibers, need to be diluted, which is very difficult without creating clusters, currently used by Quad)
- Licron, Tech Spray (resistance too low for a true ESL, large additional mass)
- ATO (needs sputtering technique, used by ML)
- EC-Coating by Martin-Jan Dijkstra
Do not use ormecon-polyanillin. This material will oxidize by time and resistance will drift away.
Any others known ?
Capaciti
if you are looking for an appropriate coating, the most important is that its not affected by humidity.
Most DIY-coatings are based on any kinds of glues. But all glue-based-coatings are not intrinsically conductive. glue based coatings form a specific surface, which "invite" water molecules to settle on the surface, thus increasing the surface conductivity. But depending on humidity the conductivity varies significantly.
Even it might still work at low humidity, the resistance is too high to allow fully charge of the membrane.
For my knowledge there are just few coating systems avaible which are permanently intrinsic conductive:
- Nylon disolved (but very high resistance, takes weeks to fully charge !!, some people dope it with ultrafine graphite)
- Baytron (modification by TDA,distributed by sigma-aldrich)
- Carbon black (epoxy with carbon-nano-fibers, need to be diluted, which is very difficult without creating clusters, currently used by Quad)
- Licron, Tech Spray (resistance too low for a true ESL, large additional mass)
- ATO (needs sputtering technique, used by ML)
- EC-Coating by Martin-Jan Dijkstra
Do not use ormecon-polyanillin. This material will oxidize by time and resistance will drift away.
Any others known ?
Capaciti
Hi I_Forgot,
The surface resistance of licron is between 10e5 and10e6, which is too low for constant charge mode for frequencies lower than 300 Hz. If you use Hybrid-concepts with crossover at about 300 Hz its still OK.
I did some measurements on thickness and added mass of a licron layer.
The thickness for a homogeneous and functional layer is at least 6 micron. due to licrons density this corresponds to the weight of about 9micron mylar. This is much more added mass in comparison to other competitive coatings available. E.g. an EC-coating layer, which is btw nearby fully transparent, adds just a weight of about 2 micron mylar.
So why to use a good coating, when better is avaiable ?
Capaciti
The surface resistance of licron is between 10e5 and10e6, which is too low for constant charge mode for frequencies lower than 300 Hz. If you use Hybrid-concepts with crossover at about 300 Hz its still OK.
I did some measurements on thickness and added mass of a licron layer.
The thickness for a homogeneous and functional layer is at least 6 micron. due to licrons density this corresponds to the weight of about 9micron mylar. This is much more added mass in comparison to other competitive coatings available. E.g. an EC-coating layer, which is btw nearby fully transparent, adds just a weight of about 2 micron mylar.
So why to use a good coating, when better is avaiable ?
Capaciti
Hi,
I will only share the formula with those I know from, they´re building a ESL. I don´t intend it to become open source. Send me a PN with a small description of Your panel for e.g.
I have to point out, that glue is one of the basic components. Its a material You can easily get in Germany. I don´t know about its availability in Amerika or somewhere else. You might have to test different glues to find the right one. On the other hand there are TNT, FedEX and others who´d be pleased to visit You.
Another component is a conductive Dope. With the add-on of this You can alter the conductivity of the coating considerably.
I don´t see any prob with varying surface resistances and humidity as the conductivity factor as long as the variation stays within certain limits. Nylon has prooved to work as Quads show and its mechanism relies on a inherent part of water (~4-6%) and so with varying resistance. Peter Walker once claimed this behaviour even as an advantage of the Nylon coating against other materials.
I used Licron for hybrid panels. Thow such coated panels perform really well, I probabely won´t use Licron any more, because I found it nearly impossible to get even coatings. Its only sold in spray cans and You can´t get an even high quality surface with those. Since I design most of my panels as optically open designs, I prefer to have highly transparent coatings. As Capacity mentioned the thickness of the Licron layer is quite high -in ESL terms of course. I doubt that with diaphragms of more than 6µm thickness You get enough bandwidth.
jauu
Calvin
I will only share the formula with those I know from, they´re building a ESL. I don´t intend it to become open source. Send me a PN with a small description of Your panel for e.g.
I have to point out, that glue is one of the basic components. Its a material You can easily get in Germany. I don´t know about its availability in Amerika or somewhere else. You might have to test different glues to find the right one. On the other hand there are TNT, FedEX and others who´d be pleased to visit You.
Another component is a conductive Dope. With the add-on of this You can alter the conductivity of the coating considerably.
I don´t see any prob with varying surface resistances and humidity as the conductivity factor as long as the variation stays within certain limits. Nylon has prooved to work as Quads show and its mechanism relies on a inherent part of water (~4-6%) and so with varying resistance. Peter Walker once claimed this behaviour even as an advantage of the Nylon coating against other materials.
I used Licron for hybrid panels. Thow such coated panels perform really well, I probabely won´t use Licron any more, because I found it nearly impossible to get even coatings. Its only sold in spray cans and You can´t get an even high quality surface with those. Since I design most of my panels as optically open designs, I prefer to have highly transparent coatings. As Capacity mentioned the thickness of the Licron layer is quite high -in ESL terms of course. I doubt that with diaphragms of more than 6µm thickness You get enough bandwidth.
jauu
Calvin
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