How to construct a cube louver (Acoustat) - Page 2 - diyAudio
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Old 5th April 2010, 03:56 AM   #11
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Yes MJ and thank you for all the advise and info.

Other questions. Can clear GE style "RTV" silicon be used to fill gaps like at the side seam where the bias wire hookup is at the mylar edge. IOW is clear silicone rubber sealant a good insulator? I've been zapped at the edge of a live panel. Just a shock not dangerous....just don't want the panel bias to "leak" off anywhere. Also is it a good idea to put a bead of silicone around the mylar edge inside where it meets the plastic frame? If silicone is no good what is?
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Old 5th April 2010, 04:04 AM   #12
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Oh forgot.
I'm in the sign business and we have many types of adhesive vinyl and mylar products and coatings. Couldn't I fish a tiny slip of clear adhesive to cover up any pinholes? The added mass would be negligible. The adhesive properties of some of the products we use is extremely strong and the thickness is down to 2 mils with some films.
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Old 5th April 2010, 04:15 AM   #13
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I should have mentioned that a very good compromise for a strong well damped panel would be to use a properly made insulated perf metal grid with an reinforcing grid of Acrylic louvre bonded to the outside surface (3/8 inch thick louvre will work well for this). You should pre treat the perf metal to remove sharp edges (an acid bath is probably the best method) and then make sure when you assemble make sure the smooth side of the perf metal faces in toward the diaphragm (this is the side where the punches push into the metal when the holes are punched). The best coating for the job is Nylon 66. The reason for this is that it is an excellent powder coat material with strong enough insulation qualities and more so because Nylon 66 has about the least amount of creep of any coating you are going to find. Creep is the term used to discribe the character of coatings to pull away from or "creep" away from sharp edges. sharp edges are where your coating will be the thinnest and so the weakest in terms of electrical insulation strength so creep is an important factor. There are better insulation materials but Nylon 66 will build up best at the edges of the punched holes and that is exactly where you will have the greatest electrical charge so it is where you need the most insulation. Since Acrylic louvre does not have the excessive plasticizer that Styrene louvre does you can glue it and paint it and everything stays put for ever. With styrene louvre there is so much plasticizer (and it varies greatly from batch to batch) that adhesive which sticks well for a while can simply float off as the plasticizer sweats out of the base material. It is junky material. That is why Jim Strickland did not use glue to bond the PVC stator wires. The liquis styrene material Acoustat used does not glu the wire down it actually encapsulates into place. The liquid styrene used was the consistancy of thick syrup made liquid by mixing methylene chloride with base stock styrene solids. The solvent then melts itself into the base styrene louvre and when the solvent off gasses you have a solid thin layer of styrene which is solvent welded to the base louvre material. It is a good idea but there are issues, the biggest is that methylene chloride is a very nasty solvent and if you have any heart issues you should not use it. Working with this solvent requires full ventilation and outside is best. Even in a garage with open doors the solvent levels will get very high. This should not be considered a safe solvent to work with if you do not have a full facial respirator and an air supply. It can result in serious problems and it is just not worth it unless you are prepared to take full precautions in using it. I can't under state this because diy types often blunder ahead into such projects without due concern, I know I have done this myself.
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Old 5th April 2010, 04:47 AM   #14
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This is how I built mine seven years ago these pics are of the smaller version 3.25" x 9.75".
I also built larger ones that are 7.75" x 22.5".
I am now getting ready to build a 4 foot version.
I was not aware the this material is available in acrylic as i have been using the readily available styrene poduct,as it works good but I to am not happy with its mechcanical strength and rigidablity.
However,both sizes still sound great and haven't had and any major mechcanical problems after seven years,just use good adhesives is all.
Does any one have a source for the acrylic version of this material? jer
Attached Images
File Type: jpg ready to be bolted back together.jpg (43.7 KB, 629 views)
File Type: jpg freshly panited staror.jpg (70.6 KB, 614 views)
File Type: jpg refurbishingold burn't stator close up.jpg (103.9 KB, 600 views)
File Type: jpg another closup.jpg (89.3 KB, 592 views)

Last edited by geraldfryjr; 5th April 2010 at 04:50 AM.
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Old 5th April 2010, 04:54 AM   #15
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I just saw you last post so I will answer here. The contact point of the diaphragm resistive coating to the small foil strip is usually not an issue. I have never found one that failed. If you are getting a little leakage to the outer edges of the panel you can avoid shock by not touching them (ha) but this is not usually an issue and a thin layer of silicon seal is not a bad idea. You should check to see it there is any diaphragm sticking out first and simply remove it with a sharp exacto blade. the reason for this charge bleeding is contamination on the surface of the diaphragm (coating side only). You can address this by using a a Q-Tip and some paint thinner and wash the clear half inch wide stretch of diaphragm around the outside of the resistive coating. There is simply a build up of cooking grease and or cigarette residue that has built up and collected dust and become conductive enough to carry the charge to the outside edge of the film where your trembling fingers await initiation to the world of working on electrostats. The solvent wash might well be enough to solve the shocking condition of handling the panels out of the frame while still charged up. You will want to invest in a high voltage probe to use with your hand held multi metre, that's a lot better than using your fingers to see if things are loaded. Say can't they pack a wallop? Just as a side not I would probably be more inclined to clean things up with paint thinner and then spray paint half a dozen wet coats of clear high gloss (greatest solids content) urethane on the panel edges. Yes this is a lot more work than silicone but it will most likely do a much better job and you wont have bits of silly cone flaking off and getting into your panels over the years. Silicone will stick but it will float right off any spot which sweats out plasticizer. More work I know just what you wanted to hear but this is like the old Fram Air Filter guy says "You can pay me now or you can pay me later". With high voltage if you don't do things right you will pay for it sooner or later.
Regarding pin holes in the diaphragm don't worry about them at all as they have zero impact on speaker performance no matter how big they get. When the stator pops an arc which jumps to the resistive coating because it looks like ground it simply burns a tiny pin hole in the Mylar diaphragm. This hole self cauterizes and it is extremely rare to ever see one of these split open and run so don't worry about them they are not an issue.
Glad to see that you are in the sign business and are adept at using solvents and adhesives for plastics. That said the very worst abuses and violations of safety issues surrounding solvent use that I have ever seen (multiple times and places) is in plastic fabrication shops. Please be careful you know better than most that these solvents and adhesives can destroy your health. Hope this answers your questions.
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Old 7th April 2010, 01:42 PM   #16
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Moray, If I have this right, after glueing the wires to the louver,
all of the loops at both ends of the louver are cut, and then soldered together with the exception of the first wire going to the panel, which goes to the transformer.
This is a better arraingment than Acoustat's "one long wire"?
Paul
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Old 7th April 2010, 07:23 PM   #17
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To answer your question all the stator wires are soldered together as one and running a wire from the transformer to both ends of the panel and connecting to the shorted stator wires is better again because you are now driving the stator length from both ends. You can modify an Acoustat this way by removing enough insulation off each stator wire to expose the wire itself then solder tagging a wire across and connecting to each wire of the grid. I don't recommend this as it is a P.I.T.A. if you cut the wire you have to patch it up and it's not much fun to do. sounds good but it is a LOT of work. So I warned you.
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Old 9th April 2010, 03:16 AM   #18
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My design goal for this was to make a speaker that was both easy to drive and efficient. I am willing to give up bass and space if necessary.
If I understand the concept right, more wires per inch will increase sensitivity.
Some people use magnet wire. I take it they do this because it comes in extremely thin gauges, and you could wind many more turns/inch.?.

Also, I'd think that if all I really was interested in was above 400 Hz the width of the panel wouldn't matter as far as bass roll off/beaming.
If I make the speaker wider do I gain in either max spl, or more importantly to me, in increased efficiency.
Thanks
Paul
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Old 9th April 2010, 05:57 AM   #19
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Yes you are right.
That is the reason I had come up with the concept of using window screen for a stator material.
It only cost around 25 cents per square foot,as wire cost $.03 to $.10 per linear foot.
One 1'x4' can cost as much as $60 per panel or more using wire,which approaches the cost of a perforated metal panel.
Not to mention the time to stretch and glue all of those wires.
And the mechinical stability of the panel from the tension of all of those wires is also in question?
I have found that wire wrap wire with kynar insulation can withstand over 10kv without a problem,but again cost is an issue.
It would probaly work good for a small panel,but I didn't find it cost effetive for a large one.
On all of my panels I used a d/s spacing between .050" to .070" with .0625" being the target and I don't seem to be having any issues with bass frequency's, as they are only 3.5" wide.
On my bigger panel however I did as they are 8" wide and 22" long.
By swapping out the .060" thick frames to .090" thick frames solved that issue, and by just raising the bias voltage seemed to makeup for the lost efficiency.
I was not able to investigat this further due to personal reasons (mentioned elsewhere on another thread) in 2003.
I am just now picking up where I had left off ,back then, like it was yesterday.
If you were to look up some of my posts you would find all of my recent research in great detail with lots of pics.
Surface area seems to be the greatest factor to consider.
For every doubling of surface area you get a 6db of gain.
I found this to be very true,by just using two small panels together instead of one almost renders my little 4.5" woofer useless except for the extreme lows.
Even at that it has a hard time keeping up and would probaly be a better match to my 8" subs.
Not bad for for two little 3.5" x 10" panels.
Which is why I have chosen the sizes I have ,was too investigate this, and utilize the material as efficiently as I can.
My bigger panels are roughly 4 times larger and this should give me a 12db gain over the ones I'm working with at the moment.
My next ones will be twice as long at 8" x 46" this should give me an extra 18db over what I started with.
I will also try a small vs large d/s spacing as well.
From what I understand a panel this size should produce some very good spl's once I get my poweramp issues solved. jer
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Old 9th April 2010, 11:19 AM   #20
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Hi,

one can have different opinions about the acoustat ESL-Panels.

As a manufacturer of ESL I need to say that those panels were state of the art at that time. You shopuld consider that we talk about a construction which was designed in the middle of the 70's !!! Todaxy you would do some things better, but the principle is sophisticated.

If someone opens an Acoustat ESL, yes you might find several issues, but did you consider how old those panels are ? 15 ,20 or even 25 years ?

Deassemble a standard 3 way system, having this age, the spider of the woofer ist briddle or even completely broken, The dome tweeter is limited by an aged magnetoferrit fluid ans so on......

Capaciti
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