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Old 26th August 2012, 02:25 PM   #161
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Join Date: Aug 2008
Default mylar procurement /spacer procurement

Seems I've exhausted all the internet sights selling polyester sheet.
The thinnest I've found is .oo1'' most places .002''

I'm wanting to redo my 2+2 at 20 wires/ inch and decreasing the d/s slightly as I'm using subwoofers for the deep bass probably crossed over at 100 Hz.

Not sure where to get the spacers as well.
Should I glue four pieces of plastic around the edge of the louver panel,
or do I need to buy sheets of plastic and cut a rectangular hole in the center?

Am going to use the cheep styrene louver as in 10 or 15 years I'll be deaf anyway, so longer life than that isn't quite necessary.

Anyway, where can I get thin "mylar" and the spacers?
Thanks,
Paul
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Old 26th August 2012, 02:58 PM   #162
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Default Plastc Strips

McMaster Carr has plastic strips. I was buying ones that were 4ft long as I recall.

I don't know about polyester film. I got mine by asking for samples.

Jim
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Old 26th August 2012, 07:15 PM   #163
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Join Date: Feb 2008
Location: Jackson,michigan
The last time I checked .5 mill or .0005" Mylar is the thinnest in suitable widths that is produced here in the US.

Thinner stuff can be found from some online model supply services, ebay or overseas suppliers
I have been able to get some really thin stuff from some elcetron microscopy suppliers such as chemplex.
But it is only produced in 3" widths that I know of maybe 4" if you are lucky.

Chemplex Industries, Inc: Thin Film Sample Supports

I meant to comment on your earlier question but I had got side tracked back then and had forgotten, Sorry.

I use window screen as my material of choice for ESL's and it works very good.
Some of my latest experiments using it can be found here,

High strength Dielectric Coatings, fact or fiction

High strength Dielectric Coatings, fact or fiction

As well as many other threads including this one (I think).

It hasn't gone without any problems but nothing that can't be solved (so far) as I had pushed them rather hard for one to end up like this,

ESL woofer- anybody game?

Here are some links and to better pictures that might give you a better idea of the construction using wire mesh,

ESL Diaphragm coating

ESL Diaphragm coating

ESL Diaphragm coating

ESL Diaphragm coating

Material for ESL

different ideas for ESL panels

different ideas for ESL panels

And many many more, One particular close up that I am looking for may be buried in one of these threads,

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

Here it is, showing the methods of connections I have tried,

ESL Diaphragm coating


I had gotten a large 4' sheet of some .020" Mylar that I cut into strips and glue along the edges to support the diagphram frames for the next 4 foot panels.

As I will use the same construction methods that I used for my smaller panels.

You can also get acetate or mylar from from hobby supplies or drafting supply houses in various thicknesses so that you can taylor the D/S to exacting specifications as needed.

As long as you use a good amount of adhesive you won't have any problems.
I used super glue and I only had to do a few repairs since they where built 10 years ago.
Only because I didn't use enough of it.
Epoxy may have been a better choice but it is very messy to work with.

Enjoy !!!

jer

Last edited by geraldfryjr; 26th August 2012 at 07:32 PM.
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Old 27th August 2012, 09:00 PM   #164
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Join Date: Apr 2010
McMaster Carr has .0005 polyester

McMaster-Carr

Jim


Quote:
Originally Posted by pforeman View Post
Seems I've exhausted all the internet sights selling polyester sheet.
The thinnest I've found is .oo1'' most places .002''

I'm wanting to redo my 2+2 at 20 wires/ inch and decreasing the d/s slightly as I'm using subwoofers for the deep bass probably crossed over at 100 Hz.

Not sure where to get the spacers as well.
Should I glue four pieces of plastic around the edge of the louver panel,
or do I need to buy sheets of plastic and cut a rectangular hole in the center?

Am going to use the cheep styrene louver as in 10 or 15 years I'll be deaf anyway, so longer life than that isn't quite necessary.

Anyway, where can I get thin "mylar" and the spacers?
Thanks,
Paul
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Old 30th January 2014, 12:33 PM   #165
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Join Date: Aug 2008
I'm wondering what people mean when they suggest to construct the esl in a way that you can dismantle it easily.
When making a Acoustat style speaker, can the front and back halves be held together either temporarily, or permanently with bolts (or something else).
Thanks,
Paul
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Old 30th January 2014, 12:58 PM   #166
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Join Date: Feb 2008
Location: Jackson,michigan
Although I have never worked with an original Acoustat panel, I see no reason that this could not be done.

My ideas for constructing ESL panels were borrowed from Acoustat to begin with and use several bolts to sandwich them together !!

I can take them apart and put them back together again as many times as a want and rarely have I ever had to re-tension the diaphragm.

Except, maybe, the First or Second time, and then after that the repeatability is 100%

I have done this at least 20 to 30 times on just one pair of panels alone with the original diaphragms that was mounted on them 11 years ago when they were built in 2003.

jer

Last edited by geraldfryjr; 30th January 2014 at 01:06 PM.
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Old 12th February 2014, 02:22 AM   #167
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Join Date: Aug 2008
when connecting the HV supply wire to the diaphragm/licron coating, do you do anything "special to ensure good contact.
I was thinking of unstranding a couple of wires and having it physically compressed between the spacers with a "tab" of the licron going into the spacer at that point.
Would an extra spray (or two) of licron in this area be a good thing?
Thanks,
Paul
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Old 12th February 2014, 02:51 AM   #168
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Join Date: Feb 2008
Location: Jackson,michigan
Yep that should work just fine.

I just used a simple sandwiched mechanical contact up against the coated side of the Diaphragm.

I didn't even use a Charge ring on my earlier models as you can see it was added later to the one shown in the pictures here,

Recoating Martin Logan Aerius Panel

ESL Diaphragm coating

And here are the ones that don't have a charge ring,

ESL Diaphragm coating

It won't hurt to use a second coat around the perimeter, but rarely have I found that I ever needed it except in the case of using the Original Formula of Licron.

That type did crack at the edge of the frame on a couple of diaphragms as it was kind of brittle and when it came off it came off in flakes.

It broke the connection at the Flex point on a few spots and they would not charge.
Of course it had to happen at the end where my connection was made.

But re-coating the edge fixed those and was when I decided to start using a charge ring as well.

Since then I always gave the perimeters a thicker coat and never had a problem since even without the charge ring using the original formula.

I never had that issue with the Crystal formula yet.

jer

Last edited by geraldfryjr; 12th February 2014 at 03:03 AM.
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Old 11th June 2014, 12:27 PM   #169
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Join Date: Aug 2008
Default Insulation thickness 600V. vs. 300V

At first I thought I was reading typo's then I found that all the sellers are saying the same thing. With PVC coated wire, 300V rated wire has a thicker insulation than 600 V wire.
I am looking to find the right wire diameter to meet my desired d/s with my (already purchased) insulator strips.
Also, as was previously discussed here, voltage rating may not need to be all that high as the wires won't touch each other. Using my Acoustat boxes with approx. 3500V (which may be raised as recommended) would a thinner insulation be better.
In other words, as long as it doesn't arc, more of the voltage drop will occur in the air gap.
But am I confusing myself, thinner insulation means higher voltage rating?
Thanks,
Paul
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Old 11th June 2014, 06:15 PM   #170
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Location: Jackson,michigan
Very interesting points.
This is something that I have planned on investigating more sometime.

It has been said that the voltage in the gap can only be raised so much due to the breakdown of the air.
I am still sceptical about this as being the maximum force that could be applied to the diaphragm.

I was able to run has high as 10Kv of bias on my panel.
every time I doubled the bias voltage I got another 6db of sensitivity out of them.

My variable supply can produce 13.8Kv with lots of current to spare.
Once I started approaching 12Kv the supply was showing signs of not being able to reach its peak voltage due to the current that was being drawn as it is regulated as well.

It was evident that corona fingers were being formed by the sound that the panel was producing but the efficiency was still yet higher from 10Kv to 12Kv.

Also the drive voltage is added to this and this was at the edge of the coating's capability and ultimately failed and it burned up at around above 20Kv to 25Kv p-p or so (I believe this includes the bias voltage).

This was also with only a .072" D/S !!

This is difficult stuff to test because once a failure occurs you basically have to start all over from scratch.
Fixing the bad spots and retesting is more time consuming than just building a new panel with the new modifications to fix the errors.

Now, this discussion has been basically about DC static voltages and insulation resistances.
What about AC drive voltages?

Roger Sanders explained to me as we were discussing what type of coatings (PowderCoatings actually) that could be used he said that "If you had two materials to chose from and one had a slightly lower Dielectric Breakdown voltage factor but had a higher Dielectric Constant (K) then chose the one that has the Highest Constant (K) over the one with the Higher Voltage Breakdown factor".

He said that the higher constant(K) raises the capacitance of the panel and increases the efficiency.
This was confusing at First, But I did somehow understand what he was saying.

It works like this,

The Stator coating is basically a very high value resistor in Parallel with a capacitor.

As explained before the resistance of the coating sets the voltage drop of the bias voltage across the resistance of the air in the gap.
At some point current will start to flow in the gap and corona fingers start to form.
If this current gets to high then the stator coating will break down and start to burn just as a regular low voltage resistor would.

The Capacitance formed by the dielectric Constant(K) raises the capacitance of the panel therefore lowers the impedance (resistance) of the circuit for the AC voltages to flow acting upon the diaphragm.

Now, When I was running the panel for the first time at about 20Kv-25Kv p-p I did have corona form within the air gap of the D/S space.
But, The resistance of the coating was high enough the it did not burn the mylar nor did it punch through it.
Much to my surprise I found absolutely no pin holes in the diaphragm!!!

Whether or not it was any louder at a level before and after the corona had formed I could not tell you as I did not have a SPL meter at the time.

I can tell you that it was so loud I had to close my ears in order to tolerate it as it was well above about 110db, I was using test tones and music as well.
I didn't notice any added distortions caused by the corona either. no harshness or crackling or anything.

The only distortion I detected with a microphone was flat topping of the waveform's from the diaphragm hitting the stator's at the lowest frequency's as expected.

It was a spectacular light show and quite loud.
But it was even more exciting after about 10 minutes of this abuse when the panel failed for the very first time and caught fire with a arc welder type arc on the side of it flowing through one of the sandwiching bolts!

Adding a charge ring was part of the cause of the failure as it was added later and there really wasn't enough room for it to be there.

The main cause of the failure was a sharp point of a wire on the edge of the wire mesh that wasn't insulated and buried deep enough in the silicone that I used to insulate the edges of the screen.

This brings me to remembering the Hair Standing experiment with a +100Kv Van De Graaff generator that only runs with a few Microamp's, and the forces that just the static charges alone apply is incredible, providing that there is no leakage current!!

I think that the voltage lost due to the current flow becuase of the breakdown of the air would make more of a compression effect of the signal rather than any noticeable distortions, if the current in the corona is kept at a minimum.

I was amazed to find that only the 13.8Kv that my supply produces was enough to flatten the PVCwire of a kinky alligator test lead that I was using on a piece of test glass that I used to insulate everything from the surface of my desk and there were no Corona Fingers being formed that I could see either.

There was about a 1/2" hill in the wire and it flattened completely to the surface of the glass and when I reduced the voltage it formed back into its original 1/2" tall bump in the wire.
I was able to do this repeatedly by varying the voltage on the supply!!

I may be wrong, But I still think that if a stator coating is strong enough to keep the current very very small that a large static voltage will still be present to be able to act forcefully upon the diaphragm (Maybe).

Meaning that a very high voltage bias could be used and very little drive voltage would be necessary to reach a certain level of SPL.

The amp loves this!!

I have already proven the concept up to 10Kv but the question is can I take it to a higher level yet, and where the actual limits is!!

I don't know of any(ones) design that has tried going to and beyond those limits.
Mostly everyone just makes them so they work.

My goal is not only how loud one can make them, as the question has been raised can they be used for PA use.
But, How much more efficiency can we squeeze out of the Technology so that they can be driven from rather small powered amplifiers.

Dayton Wright was on to something when they used S6F gas.


More on that later!!!

jer
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