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Old 9th January 2015, 05:00 AM   #1
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Default Thinking about a segmented wire stator ESL

Rather than continuing to hijack James' thread, I decided to start a new one to pick all of your brains on how to configure a segmented wire-stator ESL... starting from post #148 on James' thread.

As I've said, I'm a total dummy with electronics so please indulge my ignorance.

My initial thoughts for a wire stator to fit the 10.5" x 46.5" opening in my existing speaker frame would be:

- Black egg crate plastic louvers (florescent light diffusers) to support the wires
- Wires would be .035 copper coated TIG rods (cause I just happen to have some)... they are only 36" long so I would have to butt
and solder them to get the required length.
- I would use 13-thread/inch all thread rod to space the wires across the 10.5" open width--- omitting the two wires closest to the
spacers would leave 134 vertical wires in the grid.
- After gluing the wires in place and soldering the leads, the whole assembly would be spray coated with gloss clear polyurethane.
Any thoughts on coating thickness? (bias voltage will be only 2.7KV)
- 1/16" D/S, with seven equally spaced horizontal supports, 3/8" wide. If I opt for unequally spaced supports to distribute the
diaphragm resonance, that would require adding at least one more support spacer to meet the 100 x d/s rule.
- The diaphragm would be mechanically tensioned, primarily in the vertical direction like ML's, with just enough lateral tension to pull out
the wrinkles. Even though it's a flat panel, I figure vertical tensioning would be better in this case... any thoughts on that?
- I would use my existing tandem Farnell 230V/6V toroidal transformers, 2.7KV bias supply, and digital crossover bi-amp setup.

So now, the questions are:
- Number of wire groups required (134 wires total)
- Respective widths of wire groups
- How to configure the resistor ladder.
- Resistor values.

I'm going to attempt to download the calculator and figure it out... I'm kinda lost at this point.

Last edited by CharlieM; 9th January 2015 at 01:38 PM.
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Old 9th January 2015, 12:54 PM   #2
Bazukaz is offline Bazukaz  Lithuania
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Hi,

Some comments :

a) Why use welding rods when PVC insulated wire is available and cheap? No need to mess with spray paint & characteristics proven, like breakdown strength and correct volumetric resistance of insulation.
b) "just enough lateral tension to pull out the wrinkles" is not a sufficient measure what the tension is. For mechanically stretched membrains stretching could be in the range of around 0.5-2%. It can be easy measured by marking some dots with a permanent pen and measuring distance before & after stretching. I suggest to make some experiments to land at correct resonance frequency. High stretching(like 2% or even more) is not recommended because stability will drift significantly over time.
c) The segmentation could be as simple as this(it's somewhat similar but smaller design). More segments are needed to make off-axis response more linear, but this is perhaps good enough. The input of wire groups mean that there are 10 wires in the center, then 14 & 18 on left & right(5 segments in total). ESL_Seg program is easy to play with and no math knowledge required.

Regards
Lukas
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Old 9th January 2015, 01:30 PM   #3
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Quote:
Originally Posted by Bazukaz View Post
Hi,

Some comments :

a) Why use welding rods when PVC insulated wire is available and cheap? No need to mess with spray paint & characteristics proven, like breakdown strength and correct volumetric resistance of insulation.
b) "just enough lateral tension to pull out the wrinkles" is not a sufficient measure what the tension is. For mechanically stretched membrains stretching could be in the range of around 0.5-2%. It can be easy measured by marking some dots with a permanent pen and measuring distance before & after stretching. I suggest to make some experiments to land at correct resonance frequency. High stretching(like 2% or even more) is not recommended because stability will drift significantly over time.
c) The segmentation could be as simple as this(it's somewhat similar but smaller design). More segments are needed to make off-axis response more linear, but this is perhaps good enough. The input of wire groups mean that there are 10 wires in the center, then 14 & 18 on left & right(5 segments in total). ESL_Seg program is easy to play with and no math knowledge required.

Regards
Lukas
Thanks the the info Lukas,
Since I already have the TIG rods, I think I would want go with those. They are already straight and rigid which should make them easy to layout on the grid without having to tension them. And I think the clear coated bright copper wires on the gloss black egg crate would be give nice cosmetics.

Regarding tensioning the diaphragm, I was not intending to merely pull the wrinkles out. Rather, mechanically stretching the diaphragm to 1.5% elongation in the vertical direction only... and then applying just enough horizontal tension to pull out any wrinkles in the film.

I just tried to download the spreadsheet but I apparently cannot use it with my outdated, unregistered, bootleg copy of Excel. I'm hoping my GF has Excel on her laptop and will let me use it.

Last edited by CharlieM; 9th January 2015 at 01:35 PM.
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Old 9th January 2015, 05:12 PM   #4
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Hi , Will that spread sheet work with linux libreoffice as well? Thanks Al
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Old 9th January 2015, 05:50 PM   #5
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Hi, I'm a dummy to, probably a stupid question, if using mylar, could it not be heat shrunk to desired tension?
Thanks Al
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Old 9th January 2015, 06:25 PM   #6
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Quote:
Originally Posted by DeltaStar View Post
Hi, I'm a dummy to, probably a stupid question, if using mylar, could it not be heat shrunk to desired tension?
Thanks Al
Yes, the diaphragm in any flat panel ESL could be heat shrunk, and many builders use that method. It's certainly easier than building a stretching jig; although I doubt you could achieve the same tension.

When I built the perf-metal flat panels I'm using now, which have veritcal spacers, I used a pneumatic bike tube jig to stretched the film to 1.5% elongation in all directions-- this method gives measurable and repeatable tension and you can make the tension whatever you want it to be.

For the wire stator panels I'm contemplating now, which would use horizontal support spacers, and would be driven by discrete wire groups, I figured it might be better to tension the diaphragm predominantly in the vertical direction so as to mitigate interaction between the discretely-driven areas of the diaphragm.
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Old 9th January 2015, 06:56 PM   #7
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Charlie, the louvers you intend to use, could you post a pic of them. Thanks I presume there flourescent light covers?
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Old 9th January 2015, 07:33 PM   #8
golfnut is offline golfnut  New Zealand
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Hi Charlie

Ideally, the more and narrower the segments the better. Practically, I would make them all about 12 mm wide, perhaps as much as 15 mm. This will avoid the comb filter behaviour off axis that you can see in the plot.

Also, if all the segments are the same width you can use the same valued resistors between segments.

Rather than trying to join rods, just stack two panels one above the other - modular like. A single 36" panel will be OK for hybrid, and probably a bit sensitive to listener position (slightly different sitting down and standing up). Two 36" panels stacked on top of each other will be a good full range ESL.

If you can manage a little theory, I notice my paper (and other useful stuff) is posted at http://wireesl.weebly.com/uploads/2/...esl_theory.pdf , It gives the design equations and some explanations.

best wishes
Rod
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Old 9th January 2015, 09:31 PM   #9
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Thanks Rod,

I've got some boning up to do before starting this project and the paper you referenced looks like a great place to start.

I'm afraid two 36" panels stacked would not work for me, since the proposed wire-panels would be replacing the 12"x48" perf-metal panels in my current speakers (see link below)-- the perf-metal panels sound great but they do put your head in a vise!

Charlie

Last edited by CharlieM; 9th January 2015 at 09:34 PM.
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Old 9th January 2015, 10:25 PM   #10
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Is there any advantage in using .060 copper coated tig rod over say .020, .025, .030, .045 mig wire as thier both ER70S spec? only diff is mig comes on rolls, using the same wire spacing?

Al
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