Well I have the 4 panels’ powder coated with a primer coated and finished in black powder coated approximately three mils thick, and just contemplating constructing them this weekend. Before I begin I have several concerns I would like to defer to the experts who have constructed these ESL’s first, I constructed the pneumatic stretcher ala Charlie’s construction and wonder if there was any tips on taping the film to the jig?
Secondly, I am using two aluminum angles running parallel to each other which will serve to support the panel vertically however until they are mounted in a frame they will have some horizontal flexibility which may flex the film. Before I begin should I add a horizontal support to the vertical support and weld then together in an “H”or quasi exoskelton frame configuration?
And lastly (for the moment) this is actually 2 questions. Is there any determent in sound quality of spacing distance closer vs. further apart. I am constructing my panels 15 inches wide and with the 2 each ¾” spacers/ edge film support, the functional speaker distance is then reduced to 13 1/2”. If I divide this distance into three, the spacers distance will be under the maximum distance at 4 ½”, or using 2 spacers it will yield a distance of 6 3/4'” I believe this is just over the recommended max distance spacing using 18g. 51% open area, and hole size .1406 hole center .1875. BTW these are going to be use as a hybrid design and therefore using .063 double sided tape.
Any and all suggestions would be greatly appreciated.
Jerry
Secondly, I am using two aluminum angles running parallel to each other which will serve to support the panel vertically however until they are mounted in a frame they will have some horizontal flexibility which may flex the film. Before I begin should I add a horizontal support to the vertical support and weld then together in an “H”or quasi exoskelton frame configuration?
And lastly (for the moment) this is actually 2 questions. Is there any determent in sound quality of spacing distance closer vs. further apart. I am constructing my panels 15 inches wide and with the 2 each ¾” spacers/ edge film support, the functional speaker distance is then reduced to 13 1/2”. If I divide this distance into three, the spacers distance will be under the maximum distance at 4 ½”, or using 2 spacers it will yield a distance of 6 3/4'” I believe this is just over the recommended max distance spacing using 18g. 51% open area, and hole size .1406 hole center .1875. BTW these are going to be use as a hybrid design and therefore using .063 double sided tape.
Any and all suggestions would be greatly appreciated.
Jerry
Hi Jerry,
I used double backed tape on the bottom edges of my jig to secure the film.
The 6-micron film is strong but tears very easily if pulled from an edge-- especially if there is a nick in the cut edge. So, I use very sharp scissors to cut nice straight edges with no nicks.
The jig should have smooth radiused edges to prevent the film from grabbing and tearing-- a little car wax on the edges helps the film slide easy.
I would layout a bath towel on the work surface, then layout the film onto it. Then place the jig face down onto the film.
When you wrap the film over the edges, you don't need to pull it tight but you don't want any excess slack either. Wrap the film over the ends, then the sides, and do the corners last. Since the film will bunch up in the corners, you will need more than just the double backed tape along the jig's edge to hold it. You can use one-sided tape to finish securing the film at the corners > pulling the bunched film over and into the corners on the back of the jig, then securing with tape.
If you do happen to get a tear in the film: As long as the tear doesn't extend onto the face of the jig, you can still save it the by patching over the tear with tape.
If you are using 6-micron film, you can use the method below to measure the stretch to 1.5% elongation:
Make two 1/4" wide measuring sticks form strips of wood thin enough to be cut easily with a box knife. Make one stick exactly 12 inches long and the other stick exactly 12 and 3/16 inches long.
Take all slack out of the film, then use the 12" stick and a fine-tip felt pen to place a pair of reference marks 12" apart wide across the width of the film, about midway on the panel. Now place the longer stick next to the reference marks and slowly pump air into the tube to stretch the film.
Stretch the film until the inside edges of the reference marks exactly match the longer stick to achieve the desired 1.5% elongation.
Good luck with it!
Here is how I do it using the bicycle tube stretcher similar to CharlieM's.
I hope my pictures speak for themselves. 😀
Wachara C.
I hope my pictures speak for themselves. 😀
Wachara C.
Thanks Charlie for the tips.
Do you thing that 6 1/2" spacing is too long between spacers, or should I space them closer. If i divide the useable space between the edge support the spacing will be less than 4 1/2" using 2 verticle supports between the 2 edges instead of one?
Thanks as always,
Jerry
Do you thing that 6 1/2" spacing is too long between spacers, or should I space them closer. If i divide the useable space between the edge support the spacing will be less than 4 1/2" using 2 verticle supports between the 2 edges instead of one?
Thanks as always,
Jerry
Jerry,
I would definitely go with two vertical spacers. One reason being that with one spacer you would exceed the 70-100x d/s spacing rule (not by much but it still exceeds it). Another consideration is that it's highly unlikely that your stators are perfectly flat-- in which case there may be areas where the diaphragm is closer to a stator than you might think and thus more prone [there] to the diaphragm slapping the stator at high volume. Not to mention that the pressure waves from any subwoofers in the room will also move the diaphragms more than you might think. For these reasons, I would always opt for the low side of the 70-100x d/s spacing rule.
BTW, Wacara C,
Nice job on that jig!
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At this piont since you used Powder coating I would seriuosly consider building your bias supply and test the panels for any leakages before you assemble them.
Powder coating can some times can cause micro pin holes cuased from Gassing.
This is easily remedied from a few generous coats of clear acrylic spray.
You should have absolutely no arcing from any point on the panel and while touching the panel with using a screw driver as a sniffer probe.
A 3 mil coating is abit on the thin side, But it should get you to the 2kv to 3kv bias voltage range which is ample to make them sound very nice.
I used powder coating on my screen stators and a few samples had devolped micro cracks in the coating from excessive bending ( the coater had rolled the first sample into a tube,🙁 ).
I had them double coat them and it worked fine but seven years later I had to coat them with some acrylic in order to get to 7.5kv,But,that is an extreme range of course.
It would be a shame to have to tear them apart and a PIA after the fact.
So it would be a good measure to test them first.
Just my 2 cents worth as I have been through this several times,Cheers! jer
Powder coating can some times can cause micro pin holes cuased from Gassing.
This is easily remedied from a few generous coats of clear acrylic spray.
You should have absolutely no arcing from any point on the panel and while touching the panel with using a screw driver as a sniffer probe.
A 3 mil coating is abit on the thin side, But it should get you to the 2kv to 3kv bias voltage range which is ample to make them sound very nice.
I used powder coating on my screen stators and a few samples had devolped micro cracks in the coating from excessive bending ( the coater had rolled the first sample into a tube,🙁 ).
I had them double coat them and it worked fine but seven years later I had to coat them with some acrylic in order to get to 7.5kv,But,that is an extreme range of course.
It would be a shame to have to tear them apart and a PIA after the fact.
So it would be a good measure to test them first.
Just my 2 cents worth as I have been through this several times,Cheers! jer
Also I would stick to the 100:1 D/S rule as long as you are using a higher crossover frequency.
I have been using 150:1 as I like to dip down into the 200hz range as I can't go much lower than this with out problems due to the resonate frequency's of my panels are in the 65hz to 90hz range.
My 4" wide panels have a D/S of around .070" to .075" and I get stator clipping (slapping) slightly only when driven extremely hard and past their physical and electrical capabilities and at that point they are to loud to stand in the room with them, and, I can't even imagine what a large panel would be like.
I have heard how loud Mavric's panels get when I spoke to him on the phone several times ,and it was incredibly loud as he was shouting and need'nt be .he,he
A slight bending of the panel will not effect its performance until you get your frame built.
My only concern as I had already mentioned is excessive bending can cause micro cracks.
But powder coating is quite durable in this subject of interest, and, I really don't see much for concern as long as much care is taken to keep them from flexing excessively.
Good Luck and Keep us posted !! jer
I have been using 150:1 as I like to dip down into the 200hz range as I can't go much lower than this with out problems due to the resonate frequency's of my panels are in the 65hz to 90hz range.
My 4" wide panels have a D/S of around .070" to .075" and I get stator clipping (slapping) slightly only when driven extremely hard and past their physical and electrical capabilities and at that point they are to loud to stand in the room with them, and, I can't even imagine what a large panel would be like.
I have heard how loud Mavric's panels get when I spoke to him on the phone several times ,and it was incredibly loud as he was shouting and need'nt be .he,he
A slight bending of the panel will not effect its performance until you get your frame built.
My only concern as I had already mentioned is excessive bending can cause micro cracks.
But powder coating is quite durable in this subject of interest, and, I really don't see much for concern as long as much care is taken to keep them from flexing excessively.
Good Luck and Keep us posted !! jer
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Thank you Kindly, Jer, Charlie and Wachara C.
Well, yesterday I took the advice of Charlie and completed my power supply and performed a "probe arc test" to check for arcing through the powder coat. Well as you would expect with the estimated 3mil thick coating there was apparent arcing, mostly in the edges. I sprayed a thick of polyurethane over the entire panel. I will check again later today.
Wachara, Thanks for your pictures, I completed my diaphragm stretcher an it appears to look very similar to both yours and charlies.
Question: Hypothetically; If I would have assembled the panels that arc, and assuming the tension on the film was tensioned to say 1.5 to 2% where the diaphragm would not be easily driven into the panels with high volume, would arcing still occur? (1/16 d/s and 2kv).
Well, yesterday I took the advice of Charlie and completed my power supply and performed a "probe arc test" to check for arcing through the powder coat. Well as you would expect with the estimated 3mil thick coating there was apparent arcing, mostly in the edges. I sprayed a thick of polyurethane over the entire panel. I will check again later today.
Wachara, Thanks for your pictures, I completed my diaphragm stretcher an it appears to look very similar to both yours and charlies.
Question: Hypothetically; If I would have assembled the panels that arc, and assuming the tension on the film was tensioned to say 1.5 to 2% where the diaphragm would not be easily driven into the panels with high volume, would arcing still occur? (1/16 d/s and 2kv).
I don't think that you will arch your panel with 2KV. Unless you try to play the music extremely loud, I will not worry too much.
Wachara C.
Wachara C.
Mmmmm.... I'm hoping Jer will jump in with his thoughts on this-- I'm thinking Jer has done a lot more experimenting with stator coatings and arcing than I.
The stator edges are the areas most prone to arcing so I'm not surprised that you saw arcing there if your probe was actually touching the stator-- and especially if there are any sharp points along the edges you were probing.
The most serious mode of arcing would be stator-to-stator arcing at the panel edges, as this would involve the much higher current output from the amp; which would quickly burn thru stator insulation and get progressively worse very quickly-- and likely even trip the protection circuitry in your amplifier and shut it down.
Now that you've added some polyurethane paint, your insulation will be better. Let me now suggest that you repeat your arcing test in a slightly different way to verify if arcing would occur along the stator edges:
Pick an area on a stator edge that had arced in your earlier test. To this area, apply a layer of the urethane foam tape spacer material and let it overhanging the stator edge about 1/16 inch and tape over the edge as shown in the sketch on my blog page.
Now repeat your arc test, probing along the tape surface near the stator edge. I'm fairly sure you will now see no arcing along the edge, as any arcs would then have to shoot thru the foam tape or take the longer path around the tape overhang to reach the stator and complete the circuit. In reality, the situation is even better, as you would not coat the diaphragm all the way out to the panel edge anyway (see my blog page)-- which makes it very unlikely that you would have any diaphragm-to-stator arcing along the panel edges. Also, any stator-to-stator arcs would then have to shoot thru not one but two layers of foam tape (one layer on each stator)-- so, I'm thinking that if you tape the panel edges as shown in my blog page, it's unlikely you would have any arcing problems along the panel edges, even if your stator coating on the edges isn't so good.
As for arcing in other areas, I will defer to Jer's judgement on how best to test for that before you assemble the panels. You definitely want the side of the stator that has the smoothest hole edges facing the inside of the panel.
If you were to have arcing inside the panel after assembly, you could back off on the bias voltage. The bias supply I use isn't adjustable but you could still back off on the voltage by tapping into the diode/cap ladder at [let's say] the sixth diode rather than the lasts (8th) diode... that would drop your bias voltage from 2.7kv down to about 2kv and substantially reduce any diaphragm/stator arcing -- you would lose a bit of sensitivity but your panel would still play plenty loud (trust me on this, I've tried it).
Jump in here, Jer
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One more thing:
Rather than using a screw driver, you might try using a small trip of aluminum foil clipped to the output wire from your bias supply as the arc probe. If you still get arcing inside the panel, then tap into the bias supply at a lower voltage rung on the diode/cap ladder (as mentioned earlier) and repeat the test at the lower bias voltage (BTW, if you tap into a lower stage on the bias supply, don't forget to still route the output thru the 18Meg resistor) .
Rather than using a screw driver, you might try using a small trip of aluminum foil clipped to the output wire from your bias supply as the arc probe. If you still get arcing inside the panel, then tap into the bias supply at a lower voltage rung on the diode/cap ladder (as mentioned earlier) and repeat the test at the lower bias voltage (BTW, if you tap into a lower stage on the bias supply, don't forget to still route the output thru the 18Meg resistor) .
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Very Good ,Charlie,Not A whole lot that I can add here as You have coverd most of it.
I like Charlies method of sealing the edges with some PET tape (mylar).
I had mention using a screwdirver for two reasons,
#1 I was using voltages in Exess of 7kv and it was difficult to devise a probe where the handle didn't zap me.
#2 being as My panel is only 4 inches wide (for now) this allowed me to do a horizontal scan of the stator using the bar of the screw driver, this allowed me to cover more surface area with one swipe.
I am able to thouch the stator with the probe with no arcing and my variable bias suply wide open which can sustain a 6mm long arc and pull 12mm constant snaps.
Another test you can do is to stack the stators together using some plastic spacers first at your D/S then 1/2*D/S and also 1/4*D you can use some old cerdit cards for that spacing,and apply the bias voltage to the two stators one+ and the other-,Dim the lights and look for any blue flames ,spots or flares as these spots are leakage points and must be delt with.
If you don't see any then I doubt you will have any problems.
If you do get a solid arc through don't let it go too long!
Because what happens is that as it is arcing it is stripping of the oxogen hydrogen molecules from the material leaving the carbon behind.
At the same time it is Vaporizing the carbon and deposits a layer on the surface of the good coating in that area.
This can prove to be difficult to seal at times but not impossible.
All that you can do is clean it the best you can (with a solvent) and reseal it then test it again and repeat as may times as necessary.
If it is a large area it must be stripped down and recoated,But this is a rare occurance so don't get worried.
This shouldn't be much of an issue if you are staying in the 3kv or lower range.
But getting above 6kv-7kv proved to be a challenge, although not imposible.
I did have an arc over occur but only at the edge due to a sharp point of the screen that wasn't insulated enough.
This was a construction flaw when a built them (now 8 years ago) and was before I knew what it was like trying to contain such voltages.
Funny,When that occured I then had a ESL/Plasma speaker and literaly caught fire! he,he
I regret that I didn't get a picture of it.🙁
I was applying aprox. 25kv P-P across the stator and there was no arc through from the stators and was evident upon disassembly as there were no burn holes in the mylar and the purple flashings that I witnessed was the ionization of the air within the spacing itself.
I think I covered most of it! jer
P.S. If you have already recoated them with polyurethene then DO NOT apply any acrylic sprays as the solvent in them will cause the polyurethene to bubble and this can cause problems either/or is fine but not both,I found out the hard way.🙂
I like Charlies method of sealing the edges with some PET tape (mylar).
I had mention using a screwdirver for two reasons,
#1 I was using voltages in Exess of 7kv and it was difficult to devise a probe where the handle didn't zap me.
#2 being as My panel is only 4 inches wide (for now) this allowed me to do a horizontal scan of the stator using the bar of the screw driver, this allowed me to cover more surface area with one swipe.
I am able to thouch the stator with the probe with no arcing and my variable bias suply wide open which can sustain a 6mm long arc and pull 12mm constant snaps.
Another test you can do is to stack the stators together using some plastic spacers first at your D/S then 1/2*D/S and also 1/4*D you can use some old cerdit cards for that spacing,and apply the bias voltage to the two stators one+ and the other-,Dim the lights and look for any blue flames ,spots or flares as these spots are leakage points and must be delt with.
If you don't see any then I doubt you will have any problems.
If you do get a solid arc through don't let it go too long!
Because what happens is that as it is arcing it is stripping of the oxogen hydrogen molecules from the material leaving the carbon behind.
At the same time it is Vaporizing the carbon and deposits a layer on the surface of the good coating in that area.
This can prove to be difficult to seal at times but not impossible.
All that you can do is clean it the best you can (with a solvent) and reseal it then test it again and repeat as may times as necessary.
If it is a large area it must be stripped down and recoated,But this is a rare occurance so don't get worried.
This shouldn't be much of an issue if you are staying in the 3kv or lower range.
But getting above 6kv-7kv proved to be a challenge, although not imposible.
I did have an arc over occur but only at the edge due to a sharp point of the screen that wasn't insulated enough.
This was a construction flaw when a built them (now 8 years ago) and was before I knew what it was like trying to contain such voltages.
Funny,When that occured I then had a ESL/Plasma speaker and literaly caught fire! he,he
I regret that I didn't get a picture of it.🙁
I was applying aprox. 25kv P-P across the stator and there was no arc through from the stators and was evident upon disassembly as there were no burn holes in the mylar and the purple flashings that I witnessed was the ionization of the air within the spacing itself.
I think I covered most of it! jer
P.S. If you have already recoated them with polyurethene then DO NOT apply any acrylic sprays as the solvent in them will cause the polyurethene to bubble and this can cause problems either/or is fine but not both,I found out the hard way.🙂
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Thank you everone for your contributions and advice. I did write a post yesterday however I lost it when I tried to attach some photos of a jig I built to accurately lay down the tape across the panels...
I did re-coat the slators yesterday and there is no arcing. I do however have a question. If the bias voltage does not seem to arc during the test unless the foil actually touches the slators surface (before it was re-coated), what would be the likelyhood that it would arc at high volume, the bias voltage does not increase beyond the maximun fixed bias voltage?
Also I am following Charlie's (Bible guide) to coating my panels which should prohibit arcing on the edges as there is a 1/4" spacing distance from the edges.
Jer, I would your suggestion to use my credit card between the slators as a spacer but Im afraid it may conduct as it is a Gold Card.....sorry couldn't resist!
I am using every and all advice from everyone here!
Regards,
Jerry
I did re-coat the slators yesterday and there is no arcing. I do however have a question. If the bias voltage does not seem to arc during the test unless the foil actually touches the slators surface (before it was re-coated), what would be the likelyhood that it would arc at high volume, the bias voltage does not increase beyond the maximun fixed bias voltage?
Also I am following Charlie's (Bible guide) to coating my panels which should prohibit arcing on the edges as there is a 1/4" spacing distance from the edges.
Jer, I would your suggestion to use my credit card between the slators as a spacer but Im afraid it may conduct as it is a Gold Card.....sorry couldn't resist!
I am using every and all advice from everyone here!
Regards,
Jerry
There won't be enough gold in it to conduct,But if it is the type that has a chip in it, it would not be advisable to use.he,he
I mention using an old card because their thicknesses is in the order of .025" to .035" and would simulate a case of exetreme excursion when arcing can occur to the diagphram.
So far you seem to have a good handle on things and you shouldn't have any serious problems.
I am sure that when you start to get into high levels that the SPL will be more than what you will be expecting.
But there is always a chance of arcing at very high levels as I had pushed mine the most extreme that one could go.
As the sound from these things are so beuatiful that they really don't need to be pushed that hard,But of course there are times aswell when one wants to crank it up.
You must consider the transformation ratio and the output capabilaties of the ampilfier that you are using in order to determine the final output voltage that will be applied to the stators.
In my case I was using a small 80 to 100 watt amp with a voltage swing of 80V p-p and a transformation ratio of 1:216 this gave me 17.2kv p-p across the stators and was pretty much the limit of the amp and would shut down on any large peak as it is just a cheapy amp.
But when I switched to my Crown DC300A my output swing was 120V p-p maximum with plenty of current to spare this gave me 25.9kv p-p across the stator and this is when ionization was occuring in the gap, as I was exceeding 100V/mil ionization threshhold of the air itself.
It was when I doubled my transformation ratio when I pushed it and the thing gave way and exploded on the side near a sandwiching (mounting) screw and became a ESL/Plasma speaker.
It was extermly loud, But the sound was no where's clean either, as the amp was clipping abit ,and, the diagphram was in excursion clipping to the stators aswell as the bais voltage was being modulated by the audio due to the leakage thru the ionization.
This was what I had observed before the side exploded with an steady arc like an arc welder.
It was quite some thing to see and you could only imagine my excitement.
So then I decided to run it in this condtion for quite some time like 10 minutes or so and the only damage I found upon disassembly was the burnt acyrlic around the screw and all I had to do was to scrape off the brunt carbon and bad plastic that was left.
I then retested the stators with the bias supply and there was no leagages or failure of the stator coating what so ever except the shrap point that caused the arc over in the first place, With no holes burned in the mylar aswell.
This amazed me very much.
This I can atest to coating doing its job limiting the current in the arcs thus keeping the plasma on the cool side of things to not burn the mylar.
I never did reasemble that panel to retest it becuase at the time I had some ground loop issues with my system and tore every thing apart to rearange every thing.
Now that every thing is back workin properly the panel got damaged by my small speaker cabinet falling of the stack and put a small rip in the screen stator and cracked the eggcrate frame.🙁
Just my carelessness ,But I am pretty sure that I can repair it and get it back running again no problem.
It's just that I have been lazy and I need to finnish up some other things first so that I can focus completely on panel design and costruction again.🙂
I have been slowly getting back into it and the next thing on my aggenda is to build a pair of interface boxes because I had only breadboarded my bais supply and it is still on the breadboard and I need two of them.
If you are not sure if your coating is not thick enough then give them another coat or two,It won't hurt and any losses can be made up by increasing the bias voltage by adding another stage or two.
This will also raise your effeciency slightly aswell by raising the voltage.
There is a 6db increase in SPL every time you double the voltage.
But as you see there are maximum limits.
jer
I mention using an old card because their thicknesses is in the order of .025" to .035" and would simulate a case of exetreme excursion when arcing can occur to the diagphram.
So far you seem to have a good handle on things and you shouldn't have any serious problems.
I am sure that when you start to get into high levels that the SPL will be more than what you will be expecting.
But there is always a chance of arcing at very high levels as I had pushed mine the most extreme that one could go.
As the sound from these things are so beuatiful that they really don't need to be pushed that hard,But of course there are times aswell when one wants to crank it up.
You must consider the transformation ratio and the output capabilaties of the ampilfier that you are using in order to determine the final output voltage that will be applied to the stators.
In my case I was using a small 80 to 100 watt amp with a voltage swing of 80V p-p and a transformation ratio of 1:216 this gave me 17.2kv p-p across the stators and was pretty much the limit of the amp and would shut down on any large peak as it is just a cheapy amp.
But when I switched to my Crown DC300A my output swing was 120V p-p maximum with plenty of current to spare this gave me 25.9kv p-p across the stator and this is when ionization was occuring in the gap, as I was exceeding 100V/mil ionization threshhold of the air itself.
It was when I doubled my transformation ratio when I pushed it and the thing gave way and exploded on the side near a sandwiching (mounting) screw and became a ESL/Plasma speaker.
It was extermly loud, But the sound was no where's clean either, as the amp was clipping abit ,and, the diagphram was in excursion clipping to the stators aswell as the bais voltage was being modulated by the audio due to the leakage thru the ionization.
This was what I had observed before the side exploded with an steady arc like an arc welder.
It was quite some thing to see and you could only imagine my excitement.
So then I decided to run it in this condtion for quite some time like 10 minutes or so and the only damage I found upon disassembly was the burnt acyrlic around the screw and all I had to do was to scrape off the brunt carbon and bad plastic that was left.
I then retested the stators with the bias supply and there was no leagages or failure of the stator coating what so ever except the shrap point that caused the arc over in the first place, With no holes burned in the mylar aswell.
This amazed me very much.
This I can atest to coating doing its job limiting the current in the arcs thus keeping the plasma on the cool side of things to not burn the mylar.
I never did reasemble that panel to retest it becuase at the time I had some ground loop issues with my system and tore every thing apart to rearange every thing.
Now that every thing is back workin properly the panel got damaged by my small speaker cabinet falling of the stack and put a small rip in the screen stator and cracked the eggcrate frame.🙁
Just my carelessness ,But I am pretty sure that I can repair it and get it back running again no problem.
It's just that I have been lazy and I need to finnish up some other things first so that I can focus completely on panel design and costruction again.🙂
I have been slowly getting back into it and the next thing on my aggenda is to build a pair of interface boxes because I had only breadboarded my bais supply and it is still on the breadboard and I need two of them.
If you are not sure if your coating is not thick enough then give them another coat or two,It won't hurt and any losses can be made up by increasing the bias voltage by adding another stage or two.
This will also raise your effeciency slightly aswell by raising the voltage.
There is a 6db increase in SPL every time you double the voltage.
But as you see there are maximum limits.
jer
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Thanks Jer for your suggestions. I am hoping to continue working on my panels. I am on the fence with the possibility of increasing the bias voltage one more stage since it is over 2kv already, although I would enjoy an increase in sensitivity and sound output. My fear is that one more stage will reveal more areas that will need to be insulated. Do you think that if there is no arcing at the .025-.035 test distance there is a good chance that arcing would be unlikely at reasonable volumes? (Amplifier power output under 100wpc RMS.
I am contemplating the next step of stretching and spraying the diagraphram. It seems that 1.5% elongation is the consensus for 6um film, is 2-4% unattainable beacuse of the material characteristics?
Another forseen issue is that I will need to mask off a 1/4" area around the adges to techspray the diagraphram. Will the blues masking tape give much trouble releasing from the milar film, and how long should I wait for the spray to dry before I remove the Masking tape. I dont want to peel off the Tech Spray.
I am contemplating the next step of stretching and spraying the diagraphram. It seems that 1.5% elongation is the consensus for 6um film, is 2-4% unattainable beacuse of the material characteristics?
Another forseen issue is that I will need to mask off a 1/4" area around the adges to techspray the diagraphram. Will the blues masking tape give much trouble releasing from the milar film, and how long should I wait for the spray to dry before I remove the Masking tape. I dont want to peel off the Tech Spray.
Hi again Jerry,
I wish I could be more helpful but, since I've only built a few ESL panels and done even less testing, all I can say for sure is what worked on my panels.
My stators have at least 10 mils of polyurethane on their faces (total thickness minus metal thickness divided by two, as measured with a micrometer), the d/s spacing is 1/16" and the bias voltage is not greater than 2.7kv. I'm not having any arcing problems with this setup.
The things I don't know are how much less stator coating you would get by with or how much higher you could go with the biasing before you'd have arcing or how well the arc testing you've done would equate to actual performance in music playback.
Are your panels 15 x 48 ? Even with just 2kv bias, that size hybrid panel would put out a lot of sound without having to push huge voltage into the stators. My gut feel is that you're gonna be good to go with your stators as they are but I can't know that for sure. On the other hand, I think you could rest easy if you had a full 10 mils coating thickness on those stators.
About the diaphragm tension... I'm not sure how high you could go-- I've had two failed attempts at stretching 6-micron Hostaphan beyond 1.5% elongation. Both times the film broke at under 2%... of course, the failure could have been due to unequal tension from my jig setup but I took it as an omen to back off. 1.5% elongation I think is more tension than you'd get with a heat shrink and certainly sufficient in any case.
Are you using the bias supply shown on my blog page? If so, I would go ahead and solder up all 8-stages for 2.7kV -- you would still retain the option to back off on the voltage by tapping into the ladder at a lower stage.
Charlie
I wish I could be more helpful but, since I've only built a few ESL panels and done even less testing, all I can say for sure is what worked on my panels.
My stators have at least 10 mils of polyurethane on their faces (total thickness minus metal thickness divided by two, as measured with a micrometer), the d/s spacing is 1/16" and the bias voltage is not greater than 2.7kv. I'm not having any arcing problems with this setup.
The things I don't know are how much less stator coating you would get by with or how much higher you could go with the biasing before you'd have arcing or how well the arc testing you've done would equate to actual performance in music playback.
Are your panels 15 x 48 ? Even with just 2kv bias, that size hybrid panel would put out a lot of sound without having to push huge voltage into the stators. My gut feel is that you're gonna be good to go with your stators as they are but I can't know that for sure. On the other hand, I think you could rest easy if you had a full 10 mils coating thickness on those stators.
About the diaphragm tension... I'm not sure how high you could go-- I've had two failed attempts at stretching 6-micron Hostaphan beyond 1.5% elongation. Both times the film broke at under 2%... of course, the failure could have been due to unequal tension from my jig setup but I took it as an omen to back off. 1.5% elongation I think is more tension than you'd get with a heat shrink and certainly sufficient in any case.
Are you using the bias supply shown on my blog page? If so, I would go ahead and solder up all 8-stages for 2.7kV -- you would still retain the option to back off on the voltage by tapping into the ladder at a lower stage.
Charlie
Hi Dochungwell,
With all that you have done so far, I say you should just go for it. Do not fear so much about arching.
Wachara C.
With all that you have done so far, I say you should just go for it. Do not fear so much about arching.
Wachara C.
I use sheets of paper with one border sprayed with 3M (77) adhesive spray to mask the diagphram with.
This method forms a large post-it note type of sticky,if you will.
Just spray the border of the paper and let it dry and it forms a nice sticky that can be used a few times and does not permantley bond to the mylar and will not rip it when it is peeled off or leave any residue.
This is the method I came up with when I redid my panels last year and work great.
jer
This method forms a large post-it note type of sticky,if you will.
Just spray the border of the paper and let it dry and it forms a nice sticky that can be used a few times and does not permantley bond to the mylar and will not rip it when it is peeled off or leave any residue.
This is the method I came up with when I redid my panels last year and work great.
jer
The blue masking tape is formulated to stick weakly and peel off cleanly--which it does. As I recall, I peeled off the masking tape off as soon as the solvents flashed out and the coating lost that "wet" look (15-20 minutes I think). The coating takes several hours to completely dry and it dries so thin and sticks so well to the diaphragm that I doubt you could make it peel even if you wait until it completely dries before unmasking the edges.
I agree with charlie on the coating thickness and on the bias voltage levels.
Just for the record, the levels I stated where absolute maximums to find the limits of the panels.
I normaly run them around 5kv,I do run then as high as 6.5kv but this is the edge were mild arcing does start to occur depending on the conditions of the surrounding air (humidity).
Since my supply is variable I am able to set them at their maximum level and if any arcing happens I can just back it down.
I have mentioned before that my other set of panels that are identical in size and deminsions but use a different stator coating can not withstand anything much over 3.5kv and the start to arc profusely above that.
Although they don't sound any different than the other ones at normal listening levels.
As far as the licron crystal is concerned I have not witness any peeling so far and I have tried many different types of stress tests.
The coating cures glass clear and is so thin that I could not ( or barely) measure its thickness with a decent standard micrometer and I have not witnes any removal of the coating using denatured alcohol as a cleaning solvent after it has cured.
I have had experienced this with the old Licron formula,But it wasn't an issue as it ,too, was quite durable and retained itself even after 7 years of weather abuse as I have already documented this in another thread.
Although, I have not tried any other solvents because what I did have ,have evoporated and I need to replenish them.he,he
So masking is important so as to not get the stuff where it is not wanted as this can cause a leakage path to discharge the diagphram in an area.
Because once it is on ,it is on,and permanate!
You may find that when you spray it on,it may start to pool, I just used a wetted paper towel with licron to spread it around ,Charlie said that he had good results using a foam brush aswell.
I put it on quite wet and when it dried I was amazed that it appeared like it was never applied,that is how thin it is!
As long as you get the whole surface wetted you should not need a second coat,at least I don't recall ever using a second coat using the Crystal formula and work the first time.
jer
P.S Even should you decide to keep your bias in the 2kv to 3kv range remember that on musical peaks you can be producing as much as 15kv across the stators this is why it is so important to have adequate coating thickness on them even with your typical 100 watt amp.
Just for the record, the levels I stated where absolute maximums to find the limits of the panels.
I normaly run them around 5kv,I do run then as high as 6.5kv but this is the edge were mild arcing does start to occur depending on the conditions of the surrounding air (humidity).
Since my supply is variable I am able to set them at their maximum level and if any arcing happens I can just back it down.
I have mentioned before that my other set of panels that are identical in size and deminsions but use a different stator coating can not withstand anything much over 3.5kv and the start to arc profusely above that.
Although they don't sound any different than the other ones at normal listening levels.
As far as the licron crystal is concerned I have not witness any peeling so far and I have tried many different types of stress tests.
The coating cures glass clear and is so thin that I could not ( or barely) measure its thickness with a decent standard micrometer and I have not witnes any removal of the coating using denatured alcohol as a cleaning solvent after it has cured.
I have had experienced this with the old Licron formula,But it wasn't an issue as it ,too, was quite durable and retained itself even after 7 years of weather abuse as I have already documented this in another thread.
Although, I have not tried any other solvents because what I did have ,have evoporated and I need to replenish them.he,he
So masking is important so as to not get the stuff where it is not wanted as this can cause a leakage path to discharge the diagphram in an area.
Because once it is on ,it is on,and permanate!
You may find that when you spray it on,it may start to pool, I just used a wetted paper towel with licron to spread it around ,Charlie said that he had good results using a foam brush aswell.
I put it on quite wet and when it dried I was amazed that it appeared like it was never applied,that is how thin it is!
As long as you get the whole surface wetted you should not need a second coat,at least I don't recall ever using a second coat using the Crystal formula and work the first time.
jer
P.S Even should you decide to keep your bias in the 2kv to 3kv range remember that on musical peaks you can be producing as much as 15kv across the stators this is why it is so important to have adequate coating thickness on them even with your typical 100 watt amp.
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