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Old 19th April 2011, 12:46 PM   #1
GregH2 is offline GregH2  Australia
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Default A possible new method for ESL construction

Hi All,

I plan to build my first ESLs in the near future and have been considering various construction methods. I've just thought of a slightly different way to mount the diaphragm that I haven't seen before and thought I would run it by you all to see what you think. Everyone seems to use adhesive to hold it it place, but my proposed method employs a clamping mechanism.

What I thought of was this:

1) For the stators you need two identical peforated sheets. For this design they have to be so identical that the perforations overlie each other perfectly. The stators will need to be slightly larger than usual as the insulating spacers will be quite wide, maybe 2" in this case.

2) The insulating spacers are 2" wide strips of HDPE, PVC or whatever you like to use in your preferred thickness. They are wide so that there is plenty of surface area to allow clamping around the bolt holes described below, and hopefully prevent tearing of the diaphragm.


3) Before assembly, the insulating spacers and stators are dummy fitted without the diaphragm. The sandwich is clamped together with clamps. Working your way along the insulating strips you drill a hole every inch or two in the middle of the strips, using the locations of the holes that already exist in the stators.

4) After drilling the holes you spray the spacers with adhesive to help the diaphragm stick. You then center and tighten the diaphragm in place and temporarily clamp the whole assembly together. Hopefully the spray adhesive will help stop the diaphragm from slipping while you work.

4) You then proceed to screw nylon (plastic) bolts through the holes you drilled earlier and secure with nylon nuts (tight).


Now you have an ESL assembly with the diaphragm physically clamped in place, and hopefully the extra width of the insulating spacers will prevent tearing of the diapraghm at the bolt holes. The unit is intrinsically bolted together and should be robust. Hopefully I have explained this OK.

So, do you think this could work? Flames welcome!
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Old 19th April 2011, 01:43 PM   #2
oshifis is offline oshifis  Hungary
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Just two remarks:

- You need to span the diaphragm between two layers of spacers, so that it should be exactly in the centre between the stators
- How do you stretch the diaphragm?
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Old 19th April 2011, 01:58 PM   #3
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I hate to throw cold water on your idea but I think 2 inches of spacer width adds too much stray capacitance. As a
general rule, you want to minimize the spacer area so as to minimize the
area of the panel that adds capacitance without producing sound. *Every bit
of added capacitance increases the load on the amp and also lowers the
frequency where the treble output starts to roll off. If you can make your idea work with, let's say, 1" wide slacers, that would not add so much stray capacitance.

You might find Jonas Karud's idea of interest. Jonas uses a separate frame fir the diaphragm with stators attaché on either side via magnetic rubber spacers: Picasa Web Albums - Jonas - Drop Box.

Good luck with your project!




You might like an idea by Jonas Karud, which uses a separate frame for the
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Old 19th April 2011, 02:32 PM   #4
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The original Beveridge stators were clamped together in this way with machine screws, lock-washers and flat washers every 1-1/2" or 2" all the way around. I guess this makes rebuilding them easier (in theory), if a bit tedious to build originally, as no nuts were used--threads were hand tapped into the cast epoxy stators.
Attached Images
File Type: png Bev_ES_reflection1.png (50.7 KB, 333 views)

Last edited by david yost; 19th April 2011 at 02:37 PM.
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Old 19th April 2011, 08:47 PM   #5
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It is very tedious to bolt and unbolt screws as I did.

A big panel would be a real PIA.

I dread it when I have to take my 9" X 22" panels apart as I have a mounting bolt every 2 to 4 (2.5" average) inches which may seem like an over kill but this makes sure that there is ample presure to keep the frames from moving.

Upon disasembly I have found that the mylar has shrunk as much as 1/8" to 1/4" and is difficult but not impossible to reassemble.

I it is easier to just lay the mylar down on a peice of glass wetted with some denatured alcohol and smooth it out until there are no air bubles or wrinkles.
Then carefully tape the edges down to keep any air from getting under the mylar keeping it from moving.

You can probably skip some of this step if you are using mechanical tensioning.

Then lightley coat (really light and thin coat) a frame with some long cure time epoxy carefully drop it in to place.
Once it hits the mylar, moving it risks wrinkles to occur.
Then take another peice of glass and put it on top of the frame and weight it down.

When the epoxy starts to thicken remove the weights and carfully remove the top peice of glass as any epoxy that oozed out will stick to the glass and you will end up destroying the frame and/or the diagphram trying to seperate it from the glass if you wait to long.

I use heat treating for tensioning as I have not yet built a strecher.

It will require a major amount of clamping force to keep the tension and I don't think any thing will hold it without some form of sticky to hold and 3M 77 won't hold it.

I have read of people using contact cement but I have not tried it yet and it is very diffcult to remove from the frame should you have to replace the diagphram.

Also, I am not sure of the layer thickness consistancy of the glue when it is applied and can be very messy if not very careful causing you to waste material and time by starting over.

I have redone my same frames many times and the mylar/epoxy just peels off the acyrlic frames nicely with a razor blade and any high spots or irregularity's can be smoothed out with some 300 grit to 600 grit sandpaper on a piece of glass.

This is just my method and it works well.
I have designed my panel's to be disassembeled and reassembled repeatedly and rarely need retensioning with the heat gun when taken apart and put back together.

And, I have never had any inconsistantcy's in the performance or sound of the panel when it is back running again even after seven years since I frist built them.

I have this documented in another thread.

Hope this help you. jer

P.S. Oh boy the spacing worked this time!
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Old 20th April 2011, 12:32 AM   #6
GregH2 is offline GregH2  Australia
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Thank you all for your comments, this makes interesting reading and you have highlighted some issues I hadn't considered. I think I could reduce the spacers to 1" wide if necessary, but at the expense of requiring a lot more bolts.

Maybe it really would be too tedious, but I really like the idea of having the stator/diaphragm assembly bolted together. Will keep thinking about this. The hard part is tensioning the diaphragm and making sure it doesn't tear at the bolt holes - hence my idea to use some spray adhesive as well to reduce the tendency for things to slip.

Gerald, can you provide some more info on how you use heat for tensioning? That sounds like a neat idea.

Thanks all,

Greg.
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Old 20th April 2011, 12:50 AM   #7
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I just use a heat gun.
Be very careful not to keep it in one spot too long your you will burn the mylar.

I do it after it has been assemebled.
Once that is done then I can take it apart and reassemeble it.
If you have any spare scrap peices it is good to do I practice run to get a feel of the heat action and the melting piont of the material.
I once tried to use a hair drier gun but it wasn't hot enough.
I will find the links of when I showed how I refurbished my panels last summer. jer
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Old 20th April 2011, 01:27 AM   #8
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ESL Diaphragm coating


ESL Diaphragm coating


ESL Diaphragm coating


How to construct a cube louver (Acoustat)


And this is what happens if you don't watch what you are doing in less than 2 or 3 seconds!

different ideas for ESL panels


this is my micro panel.

Material for ESL



Material for ESL

some more pics and showing my larger panel.

Material for ESL


I used scotch double sided transparent tape on my micro panel and I am thinking about trying it on the other sizes aswell it seemed to work well and was very easy to get apart.
When I took care to seperate it gently as it held very well.

here are two more very good discussions.

Attaching ESL spacers to stators?

Diaphragm heat treatment


I hope these give you some good idea's. jer
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Old 20th April 2011, 03:49 AM   #9
GregH2 is offline GregH2  Australia
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Thank you very much Gerald. There's lots of useful links there. I'll read them all over the coming days.

Greg.
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