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Old 6th January 2012, 03:11 PM   #1
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Default Another ESL project

Hi guys

I've been reading this forum for a while now and I've decided to try to build my own pair of ESL's with dipole bass. I'll use the CharlieM's instructions as a guideline that I'll follow more or less. The D/S will be 2mm (0,078") and the stators will be made from 1mm thick perforated steel sheet with 5mm holes and 56% open area. I am not sure yet about the final size for the stator but I think it will be around 30cm x 120cm (12"x47"). The final size depends on what kind of woofer or woofers I'll end up on using.

I planned to use H-frame for the woofers. Maybe you could give me some suggestions for the drivers. Here's what I've had on my mind:
Peerless SLS 10" x 2
Peerless SLS 12" x 1
Monacor SPP-250 x 2.

SLS's has been successfully used in the dipoles and I know at least one speaker manufacturer who has used those same Monacor woofers on H-frame dipole. My listening volumes are low, usually around 70dB, and as I live in an apartment I'm not really looking for any live-like volumes or feeling the bass kicks on my chest. I believe that sets pretty easy requirements for the drivers. Still I worry that can I get enough bass with these 10" or a single 12" driver or should I simply forget about the dipole and use sealed box instead? I don't know yet to where the the low pass XO point for the woofer will be, but I think it will be anywhere in between 150 and 300Hz. I'll do some measurements with mic and REW when speaker is finished. I've got MiniDSP that does the crossover and equalization in my system.

I'll post some pics when I have something to show.
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Old 11th January 2012, 11:36 AM   #2
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Default Project continues

I finished with my bias supplies. Unfortunately I haven't had a chance to test them yet. I've been thinking about the woofer problem I mentioned on my previous post and I have decided to go with Peerless SLS 12. If it doesn't give enough kick on open baffle then I can always use it on a closed box. Or buy several pairs more and use them on OB.

Another thing that I've been thinking about lately is the stator coating. As it is winter time and the temperature is freezing cold outside I can't do the coating outside with a paintgun. I don't really have any place to do that on inside neither. On another thread the user fperra mentioned something interesting that caught my eye. Lately I've been playing around with the thought of using epoxy to coat the stators. It would give thick enough coat without fear of arcing. The only problem was how to apply it on the stators. Using the foam roller seemed like a simple and effective way and I think that's what I'll end up on using also. I need to do some more research on the subject.
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Old 11th January 2012, 02:10 PM   #3
fperra is offline fperra  United States
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Looks like you have a good start on your project. You could easily do the polyester epoxy resin coating inside, but it does give off a smell that will linger unless you open some windows after you are finished for some fresh air. Also, if you want black stators, you will still need a base color coat. You might want to consider a powder coat for that. Keep us posted.
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Old 12th January 2012, 12:53 PM   #4
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I am Glad to see another DIYer taking on an ESL Project !!!
As far as your woofer system goes try to opt for the most displacment you can afford when it come to the low end as panels that size will sail right past a single 10" woofer when you start to crank them up as you will find out once you get them built.

Nice work and Keep us posted !!!



jer
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Old 12th January 2012, 01:28 PM   #5
tyu is offline tyu  United States
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This looks great....thanks for posting the pic......can you tell me when you plug your bias tranfourmer in to the wall .....with out the panel .... Not with any amp on the primary side...can you tell me what the {ACv reading is across the panel tranfourmer Secdary..winding}??....not at the center tap....but the taps that well feed the front an back panels, just as it sets in the pic....thanks for your time..keep up the good work
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Old 15th March 2012, 10:54 AM   #6
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Default Some progress

Here's some pictures of what I've done a while ago. The working conditions were a bit challenging as you can see but so far everything's going fine. I ended up on using 18mm /0,7" birch plywood of which will get a wax coating later on.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
I just finished painting the stators for the second time and on tomorrow I'll give them the first coat of laminating epoxy. I did some preliminary testing and the the result looks nice and shiny. I hope that 2 coats of epoxy is enough. Soon after that I can finally put the stators together. I thought about using Staticide 6300 as a diaphragm coating. I contacted the manufacturer who kindly promised to send me a small sample bottle. That was 2 months ago. Anyway I haven't received it for whatever reason that is. As there is no dealer for that product here in Finland I also contacted the 2 dealers in Sweden. No reply at all. Licron would be perfect for my use but it is a bit difficult to acquire on this side of the pond. I have some other plans for the coating of which I'll write more about later on.


tuy: I haven't hooked up the bias in to the wall yet but I'll do that soon. What kind of voltages should I expect to measure between the secondary windings?
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Old 15th March 2012, 12:45 PM   #7
tyu is offline tyu  United States
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I have no way of knowing?? what are the ACV on the tranfourmer? thanks
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Old 15th March 2012, 01:39 PM   #8
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Try to get at least 5mil to 10mil's of thickness on your coating's!

I don't know what you are using as the dielectric breakdown can be any where from 400v to 2kv per mil.

The voltages can be anywhere between 5kv and 25kv depending on your transformation ratio and how hard you drive them.
Typically a 5kv peak voltage is about what to expect, and, for a panel of that size it will be quite loud as it is.

My little panel of 3.25" X 9.75" will do 102db at 1 meter with a 10V peak signal into a 1:250 transformation ratio and that is 5kv P-P.
That was using a Bias voltage of about 7kv(I think as I seemed to misplaced my data sheet for the moment).
I was pushing near 15Vpeak to 20Vpeak input when it finally failed as the panel was 9 years old too.
I was able to achieve about 25kvP-P with the other identical panel before its failure occurred on the edge from one of the sharp wire ends,that panel still works as I was able to repair it.
This is documented in another thread.

On its last run I tried to push it and the stator coating finally failed and I burned it badly.
But that was partly my fault as I failed to contend with the bad spot that it did have.
That panel is now useless.

I use wire mesh for a stator material so a repair job would be marginal,Not so for using perforated metal, although it just means more work.

Too many times in the recent past have I seen DIYer's have to tear their panels apart do too burned Diagphrams and failure of the stator coating because it was too thin.

Before you even think about mounting the diagphram's set them up in a full working order condition using some mock spacers and crank them up and make sure that you have no arcing conditions.

If you do have an arc through then your coating is not thick enough.
Also try not to let this condition last when it happens so be quick on the volume control.
Test tones would be best for the initial run then try some music as the peaks in music is when a failure would occur.
If you let the arc continue this will burn the coating and leave only the carbon atoms behind and possibly leave a layer of them on the stator surface.
They cannot be just wiped away!
This area if really bad would have to be completely stripped and redone.
Luckily this will be on the inside and won't spoil the looks of the panel.
Remember that 5Kv is one thing, But 5Kv at 100watts is a lot of burning power!!
My stator wires did get red hot !!! he,he,he


Keep on DIYin' !!!



jer
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Old 19th March 2012, 11:17 PM   #9
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Your work is neatly done. I think coating the stators is probably the hardest task that most builders face. Not everyone has access to spray equipment and I haven't tried other methods so I'm not much help with that.

Take your time and follow Jer's good advice on the coating thickness and I think you should be OK.

I only wish I could be there to see the look on your face the first time you hear your new speakers
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Old 1st April 2012, 08:17 PM   #10
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Default Stator testing

I thought that it would probably be smart thing to do the stator testing before taping the stators and diaphragm together. Could someone please explain it to an idiot on how to do it. I tried to search some info but there was nothing that I could understand. Or maybe I did but as a ESL newbie I just wanna play it extra safe. I measured my paint and epoxy coating thickness with caliper and it seems to be about 8mils thick. With my CharlieM approved bias supply it might be enough but like I said, I rather find that out now rather than later. Thx guys.
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