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Old 24th October 2012, 02:05 AM   #1
bdjohns is offline bdjohns  United States
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Default My 1st ESL build - first question!

Greetings! This is my first ESL project, though I have been planning (obsessing) about it for a long time and have been reading this forum for quite a while. I am amazed at the knowledge and generosity of those on this site. Thanks in advance for your help!
I initially was going to do a 3M tape build, but have been thinking about doing something else, to minimize the stator area that doesn't move the diaphragm. I have some extruded aluminum channel that will give me 1.72 mm d/s spacing. Also the panel would be quite rigid and may not need any other framework. Please see the attached drawing. Will this even work, with the aluminum between the stators?
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File Type: jpg Side view.JPG (47.4 KB, 489 views)

Last edited by bdjohns; 24th October 2012 at 02:33 AM.
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Old 24th October 2012, 02:34 AM   #2
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This would actually increase the un-wanted capacitance around the borders of the stators and also increase the chance of arcing in this area as well.

jer

Last edited by geraldfryjr; 24th October 2012 at 02:36 AM.
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Old 24th October 2012, 10:35 AM   #3
Bazukaz is offline Bazukaz  Lithuania
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Hi,

From my (hard) experience it's better to avoid metal parts so close to stators. Leakage problems are much more pronounced and safety might be compromised as well. From your drawing I don't understand how do you plan to isolate aluminum from the stators and mylar charging ring?
While some people have found that certain types of double sided tape do work, from my experience its not reliable in most cases under higher tension. Tapes tend to creep. Then mylar loses tension and wrinkles develop at the edges which produce unwanted noises.
My material of choice for spacers is some kind of plastic(plexi, PVC or so). PVC is a nice material in that it is not brittle but the downside is high dielectric constant(about 4), so it will increase capacitance of the panels quite much.
The best glue I have found to bond is slow-curing epoxy. It equalizes itself so surface is very flat. Full bonding strength to mylar develops after a longer time only. Epoxy has an additional advantage that it does not bond really well to most plastic spacer materials so it's not so difficult to rip it off with a knife and replace mylar if needed.
For sure, others might have found completely different methods to work the best.

Regards,
Lukas.
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Old 26th October 2012, 12:53 AM   #4
bdjohns is offline bdjohns  United States
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Thanks Jer and Lukas for your input. I definitely will abort that idea. What I am about is building something myself using creativity (from others and myself) to get great results at a low cost. So I like to use materials and tools I have or are low cost to get. The problem with that is sometimes the material doesn't really fit the purpose, which might be the case with this aluminum extrusion. I have another idea that I want to run past you. The aluminum is 6063-T6 - very rigid and painted with a durable finish. Charlie and others have said that the stators can tend to vibrate. While it may not noticeably effect the sound, it seems that it would waste energy and contribute to d/s slapping. So that is why I am trying to make a rigid panel. I would use the same extrusion to brace the panel over the internal spacers. See the pics and please let me know what you think.
Attached Images
File Type: jpg Side view 2.JPG (43.4 KB, 421 views)
File Type: jpg Iso view.JPG (57.5 KB, 409 views)
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Old 26th October 2012, 02:22 AM   #5
bdjohns is offline bdjohns  United States
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Default Stators and Coating

I am going to post a little more info on where I am so far. I bought a bunch of perforated steel shelving, so that determines the size of my panels 12.75"x 22" (324 x 559 mm). I'll start with 2 and build 2 or 4 more later. The metal is 20 gauge, 3 mm holes, 40% open area. They already had 5 mils power coating thickness on them. I sanded them pretty well and put on 3 coats of clear polyurethane with a foam roller, sanding in between coats. With rolling, I could force the coating into the holes. See the video of my contraption to keep the poly from running while drying. Panel turner - YouTube . I would try this approach again, but use a short nap roller instead of foam, as it tends to leave bubbles, that need to be sanded out. I have also sprayed a couple coats of black enamel on them. So far I have about 10 mils total coating thickness on each side - is that enough?

Note: on my previous post the 3 mm stator holes are shown way over-size. The extrusion is about 10 mm wide.
Attached Images
File Type: jpg Shelf.JPG (316.4 KB, 399 views)
File Type: jpg Solder Connection.JPG (173.4 KB, 379 views)
File Type: jpg Roller.JPG (325.3 KB, 117 views)
File Type: jpg Spray Booth.JPG (261.5 KB, 128 views)
File Type: jpg Diaphragm Side.JPG (215.6 KB, 127 views)
File Type: jpg Outside.JPG (243.2 KB, 104 views)

Last edited by bdjohns; 26th October 2012 at 02:33 AM. Reason: clarification on previous post
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Old 26th October 2012, 03:37 AM   #6
tyu is offline tyu  United States
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Vary cool thanks for the info....great thing to do with a tread mill....cook....goodluck
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Old 26th October 2012, 10:14 AM   #7
Bazukaz is offline Bazukaz  Lithuania
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Hi,

Your idea to dry paint is rather interesting.
However I would like to warn you that painting the sheets so that they can reliably withstand ~7-10 kV at home is very very difficult. So there is a high possibility of arching, leakage etc. Perhaps using higher resistance mylar coating could help to some extent.
Another problem is that panels of this size will be very directional.
IMO flat panels are much more reliable and easier to build in the end at home if made from PVC insulated wires instead of perforated sheets.
Advantages of wire panels :
1) Almost impossible to arc
2) Allows for electrical segmentation
3) Frames usually supply rigidity; no need to add additional reinforcement to prevent vibration.
4) Lower total capacitance, especially if electrical segmentation is used
5) IMO easier to build compared to properly coated perforated sheets

Regards,
Lukas.
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Old 27th October 2012, 10:38 PM   #8
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I love the rotisserie, I have an old can opener that I was going to do that with for my smaller panels.



jer
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Old 28th October 2012, 07:40 PM   #9
bdjohns is offline bdjohns  United States
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Hello again. Taking a cue from vrusso123, who also is just starting a project, to formally introduce myself. My name is Bruce. I live in northwest Iowa and work as an engineering tech at a window manufacturer. My interest in hifi audio started with a part time job at an audio store, while going to tech school for electronics repair. This was over 30 years ago. We were selling the RTR line and they had the ESR-6 stat that could be used as an add-on to their column speakers. The owner of the store had the RTR DR1’s (360 degree stat), which was an awesome speaker. That was my only exposure to ESL’s. Pursuit of this hobby was mostly on hold while raising a family, but I now have more time for it and in the last couple years I built some large enclosures for the Audio Nirvana 12 full range drivers. The bass and midrange is clean but the high end distortion is bothersome. After deciding to build some ESL’s, I acquired the Behringer 2496 crossover and bi-amped the 12’s with my Hsu Research Ventriloquist’s – that alone confirmed how much better things will sound with the ESL’s. Mostly though, I’m going off of the enthusiasm of folks on this forum! My budget is limited, so I will start with cabinets I have. Other equipment I have is a vintage Onkyo 7090 (110 wpc), Marantz receiver (30 wpc ) and an Onkyo 606 AV receiver. Expecting to need some more power for the stats, before I’m satisfied.
Just finished going through the dielectric coating thread, which has convinced me that I should add a few more coats to the stators. Thought I would try the clear insulating varnish – hoping that it will not attack the last coats of black enamel. Thanks, Bruce.
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Old 28th October 2012, 08:40 PM   #10
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Welcome to the Forum Bruce!!!

If you already have a base coat of enamel you can use some clear acrylic enamel in a spray can.
I have found that this stuff works very well.

Or some automotive type clear coat if you are using your own sprayer.
In my area I have found some Sherwin Williams brand for about $60 a gallon, with the reducer I think.
It was the cheapest that I could find in bulk and has a very high dielectric strength.

I have not tried it yet but it should work fine as well.

Some are using polyurethane with great results but I am not sure if it will bond with enamel as it might lift the base coat or bubble it.
I have had this happen to me one my earlier panels with enamel on top of polyurethane.

If you get the thicker 2x or 3x Rustoleum stuff it is very cost effective.
I have found that it is good for at least 900 volts to 1200 volts per mil or so if not more.
In some of my tests I have gotten has high as 1700 to 1900 volts per mil before breakdown had occurred.

jer

Last edited by geraldfryjr; 28th October 2012 at 08:54 PM.
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