Owned acoustat 1+1s in the 80s. Once you go ESL you never go back. Want to build my own ESLs. I've searched the web and this forum and I still have some easy questions.
1) if I use perforated steel for a stator, I only want to paint/insulate the stator side AWAY from the diaphragm, right? If you coat both sides you've got a big insulator.
2) if I use a louvre and wire, you want uninsulated wire, right? Same issue, youve got a big insulator instead of a charge surface?
3) spacers. I understand wanting spacers to keep the diaphragm from hitting the stator.
-- the spacer goes on the stator,right. You don't want the mass added on the diaphragm?
-- there is space between the spacer and the diaphragm? Why would you want a spacer applying constant pressure to the diaphragm ?
Sorry for the barrage of Qs, but the articles I read are not clear to me on these issues
Thanks in advance
1) if I use perforated steel for a stator, I only want to paint/insulate the stator side AWAY from the diaphragm, right? If you coat both sides you've got a big insulator.
2) if I use a louvre and wire, you want uninsulated wire, right? Same issue, youve got a big insulator instead of a charge surface?
3) spacers. I understand wanting spacers to keep the diaphragm from hitting the stator.
-- the spacer goes on the stator,right. You don't want the mass added on the diaphragm?
-- there is space between the spacer and the diaphragm? Why would you want a spacer applying constant pressure to the diaphragm ?
Sorry for the barrage of Qs, but the articles I read are not clear to me on these issues
Thanks in advance
1) I advise you to apply 10-12 mils of paint to BOTH sides of perf metal stators and don't neglect the edges. And before you paint it's critically important to grind smooth any sharp points along the cut edges, as sharp points focus the corona. Yes, the paint coating is an insulator but you need a certain amount of insulation in the inner face to prevent diaphragm/stator arcing and on the outer face for personal safety. While insulation does limit the electrical field strength in proportion to its thickness/dielectric strength, I contend that a painted stator can actually play louder than a bare metal panel because you can drive it harder before it starts arcing.
2) Yes, the wires on a louvered stator need some insulation too, for the same reasons as stated above. Insulated wire would not require a paint coating.
3) Yes the spacers are typically bonded to the stators and the diaphragm is bonded to spacers on one stator prior to assembling the panel. The spacers only serve to support the tensioned diaphragm at the proper distance from the stators.
My website below is a fairly comprehensive guide for building perf-metal ESL's. Most of the info there was learned from the other builders on this forum.
Jazzman's DIY Electrostatic Loudspeaker Page
Charlie
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Hi,
1) in simple Theory Your idea would work .... in deeper theory and hard praxis it won´t
2) dito
3) the task of a spacer is not to appl a constant pressure, but to assure that the diaphragm remains centered between the stators and that the free vibrating area remains small enough that the diaphragm won´t touch the stator when playing loud. Besides radiating a kind of rattling noise the membrane will stick for a moment to the stator.
jauu
Calvin
1) in simple Theory Your idea would work .... in deeper theory and hard praxis it won´t
2) dito
3) the task of a spacer is not to appl a constant pressure, but to assure that the diaphragm remains centered between the stators and that the free vibrating area remains small enough that the diaphragm won´t touch the stator when playing loud. Besides radiating a kind of rattling noise the membrane will stick for a moment to the stator.
jauu
Calvin
OK, so the coating on the stator isn't an insulator, it is a dielectric (nonconducting but polarizable). Polyurethanes have dielectric properties (but the devil is in the details...).
It would seem that the coatings used would be important. Is that not what you guys have found in practice?
BTW, thanks for the site Jazzman, I've read it cover-to-cover about 6 times.
It would seem that the coatings used would be important. Is that not what you guys have found in practice?
BTW, thanks for the site Jazzman, I've read it cover-to-cover about 6 times.
If you were to add a dielectric powder (aluminum oxide) to a polyurethane coating (automobile clear-coat), wouldn't you improve efficiency? Or am I worrying about butterfly breaths in a hurricane?
I'm just concerned that polyurethane along defeats a lot of the benefit of high voltage -- with a good dielectric couldn't you run with a lower voltage and get the same efficiency?
I'm just concerned that polyurethane along defeats a lot of the benefit of high voltage -- with a good dielectric couldn't you run with a lower voltage and get the same efficiency?
Hi,
adding additives with high-K (esp. high epsilon-r, Er) increases the capacitance of the insulative layer and reduces the AC-voltage drop over the insulator.
It forms a capacitive voltage divider with the air-layer.
As the thickness is usually considerably lower than the air-layer and since the commonly used plastics feature Er values ~3-5, the isolator-capacitance is already 10times or more higher than the air-capacitor.
This on the other hand means less than 10% losses over the isolator-layer.
So, yes a high-Kadditive would improve efficiency, but .... as usual there´s a ´but´.
High K-dielectrics behave non-linear and they also may reduce the flashover treshold and the increase in efficiency may not be worthwhile.
If You´d for example cast a thick stator from epoxy with the conductive layer of the stator to the outside, You´d need a high-K additive.
See the Beveridge stators.
In the case of ESLs where the stator-area equals the diaphragm area, Er (or K) and the thickness are related inverse proportional.
A 5mm thick insulator with a Er of 5 will result in the same capacitance as a 1mm air layer.
A 0.5mm insulator with a Er of 5 has ~10times the capacitance of a 1mm air layer.
A 5mm thick insulator required a Er of 50 for the same 10:1 ratio.
The major difference would be in the much higher flashover treshold of the 5mm insulator.
jauu
Calvin
adding additives with high-K (esp. high epsilon-r, Er) increases the capacitance of the insulative layer and reduces the AC-voltage drop over the insulator.
It forms a capacitive voltage divider with the air-layer.
As the thickness is usually considerably lower than the air-layer and since the commonly used plastics feature Er values ~3-5, the isolator-capacitance is already 10times or more higher than the air-capacitor.
This on the other hand means less than 10% losses over the isolator-layer.
So, yes a high-Kadditive would improve efficiency, but .... as usual there´s a ´but´.
High K-dielectrics behave non-linear and they also may reduce the flashover treshold and the increase in efficiency may not be worthwhile.
If You´d for example cast a thick stator from epoxy with the conductive layer of the stator to the outside, You´d need a high-K additive.
See the Beveridge stators.
In the case of ESLs where the stator-area equals the diaphragm area, Er (or K) and the thickness are related inverse proportional.
A 5mm thick insulator with a Er of 5 will result in the same capacitance as a 1mm air layer.
A 0.5mm insulator with a Er of 5 has ~10times the capacitance of a 1mm air layer.
A 5mm thick insulator required a Er of 50 for the same 10:1 ratio.
The major difference would be in the much higher flashover treshold of the 5mm insulator.
jauu
Calvin
Calvin's explanation of the capacitive voltage divider formed by the insulation and the air gap is spot on. Even wire having a thick PVC insulation layer results in losing only ~1dB of sensitivity compared to un-insulated wire stators with the same air-gap.
I think the take-away is that as long as your insulation thickness is < 1/4 of your air gap thickness, no special measures need to be taken to increase the dielectric constant of the insulator. Happily, this is nearly always the case.
Besides the capacitive voltage divider, there is also a resistive voltage divider that defines the distribution of your HV bias supply between the airgap and the insulation. Insulators with lower bulk resistivity(like PVC) result in a higher portion of the HV across the air gap and thus higher sensitivity.
More details on this subject here:
http://www.diyaudio.com/forums/plan...truct-cube-louver-acoustat-7.html#post2154621
Here are few very very informative threads on stator coating coatings.
http://www.diyaudio.com/forums/plan...ectric-coatings-fact-fiction.html#post2779101
http://www.diyaudio.com/forums/planars-exotics/261177-stator-coating.html#post4039053
http://www.diyaudio.com/forums/planars-exotics/245105-prime-not-prime-question.html#post3686982
Do read through them completely !!!
As Calvin pointed out there are benefits to using a coating that has a high K factor.
Beware of which type of additive you use such as Titanium Dioxide, It has a very high K rating but it is also conductive at high voltages.
Mainly it is used as a white pigment in paints and gray primers, Stay away from these types of paints as I explain the reasons in detail in the above threads.
I get great results from your normal Red Spray Can type primers, it uses Talc as the filler, and, It too has a high K factor as well and it is also an excellent insulator.
I show my test results using just common Clear Spray Acrylic Enamel and the Red Spray primers.
The only time I would use a gray primer is if it is an etching type for the First coat on bare metal and use the other for your build up to your final thickness.
Cheers!!!
jer
http://www.diyaudio.com/forums/plan...ectric-coatings-fact-fiction.html#post2779101
http://www.diyaudio.com/forums/planars-exotics/261177-stator-coating.html#post4039053
http://www.diyaudio.com/forums/planars-exotics/245105-prime-not-prime-question.html#post3686982
Do read through them completely !!!
As Calvin pointed out there are benefits to using a coating that has a high K factor.
Beware of which type of additive you use such as Titanium Dioxide, It has a very high K rating but it is also conductive at high voltages.
Mainly it is used as a white pigment in paints and gray primers, Stay away from these types of paints as I explain the reasons in detail in the above threads.
I get great results from your normal Red Spray Can type primers, it uses Talc as the filler, and, It too has a high K factor as well and it is also an excellent insulator.
I show my test results using just common Clear Spray Acrylic Enamel and the Red Spray primers.
The only time I would use a gray primer is if it is an etching type for the First coat on bare metal and use the other for your build up to your final thickness.
Cheers!!!
jer
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