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Old 2nd December 2013, 08:41 PM   #1
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Default First time ESL builder

I am embarking on my first ESL build and I have some questions. However, first let me put them into context:

I'd like to build a set of tower ESL's (hybrid) and I was planning on using Charlie's (Jazzman) blog as a guide of sorts.

These speakers are meant for mixed use, although probably more HT than music. I have a theater room with projection screen and speakers approximately 12 feet from the seating. I have a lot of seating and I understand that dispersion will be an issue with a large crowd. However, the room is mostly used by the wife and I so I consider the dispersion to be a reasonable sacrifice if it can work for the two of us. Plus I will continue to use traditional cone center channels (unless an ESL solution with a workable geometry presents itself) so dialog will be the same.

Anyways, my question is mostly about vertical spacer distance. Is there a dispersion benefit to making the center section narrower than the other two (3 total sections)?

The diaphragm width (accounting for 2 vertical spacers) will be about 10.25". I was thinking something like 2" for the center section and 4.125" for the outside sections.

Or is 2" too narrow?
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Old 2nd December 2013, 11:41 PM   #2
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Quote:
Originally Posted by jamesthomas128 View Post
Is there a dispersion benefit to making the center section narrower than the other two (3 total sections)?
Unfortunately no.
Dispersion(or lack there of) will be the same no matter what section widths you choose since you are driving all sections with a full bandwidth signal. For best diaphragm stability 3 equal width sections is best(ie keeping unsupported width of any/all sections to a minimum).

There is something to be said for using 3 staggered section width as it lowers the Q of the diaphragm resonance somewhat. However, if you are following the Jazzman guide, you will be using an active crossover which allows very sharp roll-off below crossover effectively removing the diaphragm resonance issue.

Last edited by bolserst; 2nd December 2013 at 11:47 PM.
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Old 3rd December 2013, 12:32 AM   #3
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Hi James,
Bolserst's advice is spot on as usual. My panels have equal spans between the spacers for stability. Using different spacer spans would decrease the loudness of the diaphragm resonance a bit, but only at the expense of widening the resonance band, so, no real advantage there, I figure. And I use a really steep crossover slope to prevent exciting the diaphragm resonance, so that's not really a problem.

Since my panels use one-piece perf metal stators, they can't be segmented electrically, as can be done with wire stators to allow sending different frequency bands to individual wire groups, and thereby change the dispersion.

So, if you want wider dispersion from perf metal panels, you will have to make them curved. Curved panels take more effort to build but it's do-able. All else could remain the same except you could not tension the diaphragm with a bike tube stretcher jig because you would need to tension the film in the vertical direction only. And you could not use a beam splitter like mine behind a curved panel.

I can assure you of one thing: Flat panels the width of mine are the most beaming, directional speakers you will ever hear. This gives them superior slam and imaging, but at the expense of a miniscule and very pronounced sweet spot. And they are magical indeed, in the sweet spot! I have to admit, though; as much as I love their sound, I do find myself wishing for a wider sweet spot whenever I have guests.

Good luck with your project!

Last edited by CharlieM; 3rd December 2013 at 12:43 AM.
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Old 3rd December 2013, 01:10 AM   #4
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Thanks for the quick feedback guys!

I actually think there might be some advantage to widening the resonance band as I hope to eventually design some passive crossovers for these. I think that the wider but shorter peak could be easier to deal with with conventional crossovers. Or would it be best to keep it narrow and simply use a notch? Interesting question.

I will start off with a minidsp for active crossover/eq, though.

I don't think that I have much interest in attempting curved panels unless somebody has a good solution for tensioning the diaphragm. Also, I thought that I read somewhere that the dispersion benefits of curved panels are limited.... I would be willing to give it a try, however.

Anyways, I would like to widen the dispersion as much as is reasonable. Do you gentlemen have any suggestions? Are curved panels a reasonable solution? I guess that I haven't seen any detailed DIY curved panel experiences that convince me.
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Old 3rd December 2013, 01:59 AM   #5
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I've been daydreaming about building a removable, slant-plate acoustic lens, consisting of multiple plates of clear plexiglass. When guests come over, the lens could be attached at the front of the panel like a grill to widen the dispersion, and then removed later for solo listening. Some JBL horns used this type lens to good effect.

Last edited by CharlieM; 3rd December 2013 at 02:01 AM.
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Old 3rd December 2013, 04:38 AM   #6
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Perhaps I will consider the use of curved stators. I guess the question is what curvature would be reasonable on a 12x48 panel? Maybe 20 degrees?
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Old 3rd December 2013, 04:07 PM   #7
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I think that a electrically segmented ESL is an easier and better method of dealing with getting a better horizontal dispersion.

It also it has many benefits as too being an easier load on the amplifier as well.

Segmented Wire Stator ESL simulator (esl_seg_ui)

I have found the use of TIG welding rod greatly eases the construction of such a design as I have done here,

A Segmented Stator Desktop ESL

I would suggest to use a thinner Diameter Rod such as .045" if you can get it as it available as well.
I will be getting some of that size for my next larger builds as you have to add the coating thickness to get your overall diameter and open area spacing.

As a First time builder my suggestion would be to build a smaller panel to start with.

You can get some very amazing results for a a smaller panel of only 3" to 5" of width and from say 6" to 20" or so of length.

Smaller panels do perform well and are easier to work with due to there size.

But the foremost thing is that they cost much much less to build and allows you to get familiar with the construction and the workings of an ESL.

Should something do go wrong you won't be out as much $$$ in materials should you find that whatever problem you run into can't be fixed!!
I have seen this happen many times over just in the last year.

I it cost me less than $30 to make my very First panels 10 years ago using only aluminium window screen and plastic lighting grate material and cans spray paint, stuff commonly found at your local hardware store such as Lowe's or Home Depot.
And they still work today ( with the exception of one panel...He,he,he,he)!!!!
Here are two of the many versions I have made,

Budget ESL

How to construct a cube louver (Acoustat)

different ideas for ESL panels

ESL Diaphragm coating

I had a larger sized panel of 7.75" X 21.5" and I can't find the link but it is somewhere in these threads.
It was my very First panel and it was a side by side picture of the two different sizes as it was 4X times large than the size of the panel in the above posts.

It is much cheaper to do than using perforated metal should you be on any sort of budget.

Aluminium Lincane sheet is another alternative that works well for stators providing a proper support frame is made as it is fairly thin stuff.

The metal MUST BE EXTREMLY FLAT!!!
With absolutely no warps or creases in the material!!

Now, I may sound very critical here, But I am not exaggerating by any means!!

Do, Be very selective in your materials quality as it is not cheap these days as this can be hard to maintain or even acquire when working large metal panels.
Although however, It is not impossible.

ESL's can be very easy to construct providing one follows the procedures that many of us have already sacrificed through trial and error.

Charlie's build is a very good example and a fellow DIYer Mavric has dedlcated few threads to such a construction using Charlies methods and help here,

Start to Finish ESL Hybrid

Material for ESL

There is a lot going on as to how they work and it is not something easily learned over night.
But with a lot of reading and persistence you will find this a very very rewarding hobby.
Once you have built your very First working panel(s) the moment will be priceless!!!

Here is a compilation of many of the Greatest links to help get you started,

Help, Advice, Information, Reassurance... ???

How to construct a cube louver (Acoustat)

Good Luck !!!

jer

P.S. Please do consider these factors before attempting a curved stator for a First time build.

Last edited by geraldfryjr; 3rd December 2013 at 04:12 PM.
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Old 3rd December 2013, 04:11 PM   #8
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Thanks for all of the advice. After some more reading I think that a segmented panel could be doable. The fact that I have a large CNC machine and McMaster Carr has copper clad pcb at a reasonable price is pointing me in that direction.
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Old 3rd December 2013, 04:17 PM   #9
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That is also a very good path to consider providing you have the tools and/or patience to drill all of those holes.
Etching the copper away from the edges of all of the holes is another issue as well.
I wished I had seen your post as I just had opened the page that was discussing such issues.

jer

Last edited by geraldfryjr; 3rd December 2013 at 04:20 PM.
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Old 3rd December 2013, 04:56 PM   #10
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With the cnc router I can machine away the Cu thus removing the need to etch. Also, I can machine slots (or have the machine drill holes). But the point is that machining the stators is not an issue for me.

This could be interesting. I was hoping that I would have some excuse to CNC something on this project....
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