Excerpt from THE B.A.S. SPEAKER Vol.5, 1976
Beveridge Loudspeaker:
"...The diaphragm is aluminized mylar, whose good conductivity helps eliminate problems caused by static electricity in other electrostatics.The electrodes are 250 thousandths of an inch thick, with a conductive coating on the outside, and are made of epoxy with barium titanate mixed in. This material has a dielectric constant of 100, so that even though the air gap between the diaphragm and the inner side of the electrode (80 mils) is less than 25% of the total distance to the outer conductor, almost 97% of the voltage drop between the two occurs across the air gap, right where it's wanted..."
Harry
Capaciti:yes that's a very good point to bring up as it always seems to get forgotten. I used to work with a fellow who was a very good friend of Jim Strickland and I was told the stock film was HS65 though I am sure they played with the range of HS materials and probably others in the prototype stages. My friend did a bunch of parallel prototype work on Acoustats in the early days. I got some rolls of both HS65 and HS80 and later some HS150 for a planar magnetic project.
The second set of panels that I built were 9 inch wide cube louvre with a central clamp to divide the panel section in half and I used HS65 film, there was no need for the felt pads with these panels. They did not go as low as a stock panel though it seemed as if they did because they were much better controlled in the bass.
I think that narrower panels with lighter diaphragms crossed over to subs make the most sense but that is just my take on it. I agree that you can't clone an Acoustat and use 3 micron film (keeping everything else stock) because it won't work properly and it won't be an Acoustat any more. That was my point previously about hot rodding you can do a little but you can only go so far until you have built something different and it's not a clone any longer. If you decide that you want to make things better then you have to choose a different set of compromises for your new design project.
The second set of panels that I built were 9 inch wide cube louvre with a central clamp to divide the panel section in half and I used HS65 film, there was no need for the felt pads with these panels. They did not go as low as a stock panel though it seemed as if they did because they were much better controlled in the bass.
I think that narrower panels with lighter diaphragms crossed over to subs make the most sense but that is just my take on it. I agree that you can't clone an Acoustat and use 3 micron film (keeping everything else stock) because it won't work properly and it won't be an Acoustat any more. That was my point previously about hot rodding you can do a little but you can only go so far until you have built something different and it's not a clone any longer. If you decide that you want to make things better then you have to choose a different set of compromises for your new design project.
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I'm confused. All the Acoustat literature states .00065 inches as the thickness of their membranes, which would equal .0165 millimeters. Am I missing something? I'm quite ignorant regarding these materials but maybe there's a naming convention I'm unaware of, or the Acoustat literature was inaccurate? Thanks!
Hi,
originally the thickness was 0.8 mill, which is about 0,021mm or 21micrometer, later the thickness was reduced to 0,65 mill, which is about 0,0165mm or 16,5 micrometer. As moray mentioned those thicknesses is more forgiving in the high frequency range, if records are critical, but on the other hand the acoustats sounded a little bit less detailed.
e.g.:
ML: 0,5 mill, 12 micrometer
Audiostatic: 0,25 mill, 6 micrometer
Quad: 0,13 mill, 3 micrometer
Capaciti
originally the thickness was 0.8 mill, which is about 0,021mm or 21micrometer, later the thickness was reduced to 0,65 mill, which is about 0,0165mm or 16,5 micrometer. As moray mentioned those thicknesses is more forgiving in the high frequency range, if records are critical, but on the other hand the acoustats sounded a little bit less detailed.
e.g.:
ML: 0,5 mill, 12 micrometer
Audiostatic: 0,25 mill, 6 micrometer
Quad: 0,13 mill, 3 micrometer
Capaciti
I read in another post that some people have used saran wrap.
It is now made from polyethylene. The site says its .5 mils.
Is this at all suitable. When deciding on the suitability of a membrane. Conductive coatings really don't stick well to anything, so is there any other consideration besides thickness and width.
I also saw a site telling how thin packing wrap was you can get as thin as 120 guage.
Can you flame treat any of this stuff.
I don't understand how people treat the membrane with a flame.
Sheesh, I would think it would just disolve.
Paul
It is now made from polyethylene. The site says its .5 mils.
Is this at all suitable. When deciding on the suitability of a membrane. Conductive coatings really don't stick well to anything, so is there any other consideration besides thickness and width.
I also saw a site telling how thin packing wrap was you can get as thin as 120 guage.
Can you flame treat any of this stuff.
I don't understand how people treat the membrane with a flame.
Sheesh, I would think it would just disolve.
Paul
Saran will work but not for very long as it tends to keep stretching and lose its tension.
I have used some model airplane coverings with good results on my first frame,but enventualy I started using the .25mil mylar that I have.
There are only a few sources that I know of here in the states that you can get the thin stuff from.
But .5 mil is pretty is pretty common and monokote is close to it once you wash off the adhesive coating with acetone.
there was one I tried called ultra or super ultrakote or something ,that I liked.
It had a soft spongey feel like saran with a thickness of around .3mil to .5mil but held its tension like mylar and was supposed to be resistant to temperature changes.
They are all p.e.t. type films (except saran) and I still have some of them.
Once I get my electronics squared away I will start building some frames again and post the results of the different types of films I have. jer
I have used some model airplane coverings with good results on my first frame,but enventualy I started using the .25mil mylar that I have.
There are only a few sources that I know of here in the states that you can get the thin stuff from.
But .5 mil is pretty is pretty common and monokote is close to it once you wash off the adhesive coating with acetone.
there was one I tried called ultra or super ultrakote or something ,that I liked.
It had a soft spongey feel like saran with a thickness of around .3mil to .5mil but held its tension like mylar and was supposed to be resistant to temperature changes.
They are all p.e.t. type films (except saran) and I still have some of them.
Once I get my electronics squared away I will start building some frames again and post the results of the different types of films I have. jer
Quote: When deciding on the suitability of a membrane. Conductive coatings really don't stick well to anything, so is there any other consideration besides thickness and width.
I also saw a site telling how thin packing wrap was you can get as thin as 120 guage.
Can you flame treat any of this stuff.
I don't understand how people treat the membrane with a flame.
Sheesh, I would think it would just disolve.
Paul
Paul there are at least three or more currently available resistive coatings (designed specifically for this application) which are available on line all of which work and don't cost too much. There are several commercial products which are available that will do the job there are home brew recipes that work there is liquid nylon which has the longest successful life span of any coating known (that's what Quad used) You have a host of resistive coating options all of which will stick to Mylar. You have lots of choices for resistive coatings.
As for diaphragm material there is HS Mylar there is C grade Mylar there is Hostaphan (polyester) and all sorts of people who will sell in small quantities so you have plenty of options. ER Audio in Australia has parts materials films down to 3 micron take a look here Electrostatic Loudspeakers By ER Audio. Film at 120 gage is not suitable forget it. Quad ESL 63's are 3 micron C grade Mylar many other ESL's ar 6 micron Roger Sanders ESL's are 12 micron Acoustat's are 65 mil HS Mylar (that's 65 gage). The thickest film that I would use is 80 gage HS Mylar. Save yourself a lot of grief and unnecessary expense and just buy the right stuff first because your diaphragm film is only a small portion of the cost of building an ESL anyhow. Six micron (0.25 mil) is an excellent choice and it is good to work with and will last a life time.
Flame treatment (plasma or corona treatment) requires high tech production equipment so no you cannot flame treat your film because you were right it would burn. But if you really want it you can buy corona or plasma treated film and yes it will make a better surface for your resistive coating but it is not required for you to build with and I am not aware of any commercial ESL's which use such treated film (I am sure that someone will now name one). You can check out Mark Rehorst's site it has a wealth of practical information and helpful information. Sheldon's site is also a must Quad ESL Refurbishing and Sheldon's Audio Designs. You can buy parts including powder coated panels from Russ default A must site for reference information is Gary Jacobson's Quad site almost tooo much information Home and last but not least The Izzy Wizzy Mod Page Izzy Wizzy Audio Have fun reading and when you are done you will know or have access to just about all there is. Hope this helps Moray James.
I also saw a site telling how thin packing wrap was you can get as thin as 120 guage.
Can you flame treat any of this stuff.
I don't understand how people treat the membrane with a flame.
Sheesh, I would think it would just disolve.
Paul
Paul there are at least three or more currently available resistive coatings (designed specifically for this application) which are available on line all of which work and don't cost too much. There are several commercial products which are available that will do the job there are home brew recipes that work there is liquid nylon which has the longest successful life span of any coating known (that's what Quad used) You have a host of resistive coating options all of which will stick to Mylar. You have lots of choices for resistive coatings.
As for diaphragm material there is HS Mylar there is C grade Mylar there is Hostaphan (polyester) and all sorts of people who will sell in small quantities so you have plenty of options. ER Audio in Australia has parts materials films down to 3 micron take a look here Electrostatic Loudspeakers By ER Audio. Film at 120 gage is not suitable forget it. Quad ESL 63's are 3 micron C grade Mylar many other ESL's ar 6 micron Roger Sanders ESL's are 12 micron Acoustat's are 65 mil HS Mylar (that's 65 gage). The thickest film that I would use is 80 gage HS Mylar. Save yourself a lot of grief and unnecessary expense and just buy the right stuff first because your diaphragm film is only a small portion of the cost of building an ESL anyhow. Six micron (0.25 mil) is an excellent choice and it is good to work with and will last a life time.
Flame treatment (plasma or corona treatment) requires high tech production equipment so no you cannot flame treat your film because you were right it would burn. But if you really want it you can buy corona or plasma treated film and yes it will make a better surface for your resistive coating but it is not required for you to build with and I am not aware of any commercial ESL's which use such treated film (I am sure that someone will now name one). You can check out Mark Rehorst's site it has a wealth of practical information and helpful information. Sheldon's site is also a must Quad ESL Refurbishing and Sheldon's Audio Designs. You can buy parts including powder coated panels from Russ default A must site for reference information is Gary Jacobson's Quad site almost tooo much information Home and last but not least The Izzy Wizzy Mod Page Izzy Wizzy Audio Have fun reading and when you are done you will know or have access to just about all there is. Hope this helps Moray James.
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Paul: a film treated to have a matte finish on one side would not only be good for resistive coating adhesion but also for what ever adhesive you are going to use to mount the diaphragm to the stator spacers (on one side anyway). Check and see what grade of base film this is on and down to what thickness. Can you purchase it in small quantity or do you have to buy a roll?
I just noticed that I missed attaching the link for Mark Rehorst's web site (in the above post) Mark Rehorst's Projects Page
I just noticed that I missed attaching the link for Mark Rehorst's web site (in the above post) Mark Rehorst's Projects Page
The hot melt glue I used came from McMaster-Carr. The label on the bag says "Surebonder, 1 lb., 1/2" x 15" high performance, 707R15-1-HP." Yes, you can reheat it after applying it, in fact that became a key step in my approach. I put a bead of hot melt glue along each cross-brace before stringing the wires, and then used a heat gun to remelt the glue. While the glue was soft I used a piece of aluminum angle (covered with packing tape so the glue wouldn't stick) to press the wires into the melted glue and ensure no excess glue was squeezed into the stator/diaphragm gap.
The downside of this approach is that it requires gluing of the wires to the cross-braces one cross-brace at a time. The nice feature is that if something doesn't work as well as you'd like on a particular cross-brace, you can remelt the glue and fix it without having to tear the whole assembly apart.
I tried other wire stretching schemes before I decided to use the one I described. I ended up really liking the ability to tighten individual 1 cm wide sections of wire without having to do anything to the neighboring sections of wire so that I could get everything uniformly stretched. It's not a perfect system, and there may be a simpler way to achieve similar or better results, but my simpler attempts yielded poorer results. Nonetheless, it's easy for me to believe that I missed the boat somewhere and that something that I didn't try would have been both simpler and better.
Few
Few: thanks very much. I just went to Superbonders home page and asked for information regarding this product.
As for your stretching jig I am sure that it is in every way nicer than mine which is dead simple but is fast and easy to build. I just wanted something that would work and be easy to adjust but more importantly be something any one could knock up to get the job done. Since I use such a small gage wire hand tension is all that is required.
As for your stretching jig I am sure that it is in every way nicer than mine which is dead simple but is fast and easy to build. I just wanted something that would work and be easy to adjust but more importantly be something any one could knock up to get the job done. Since I use such a small gage wire hand tension is all that is required.
The one thing that Roger Sanders told me ,that always stuck in the back of my mind, when we were talking about stator coatings (powder coatings was the subject) is " of course you want the highest dielectric strength but choose the one that has the highest dielectric constant even though it has a lower dielectric strength(volt per mil)".
Somehow I understand this but it is very confusing and I have never found any discussions of this or it being mentioned. jer[/QUOTE]
On the web, I found a list of dielectirc constants of different materiels. Of all the ones discussed, urethane has the highest value. Does this mean that heavy build magnet wire with out kinar or teflon or... would be best.
Also I was wondering about the termination of the wires on the egg crate.
Do you cut the wires (top and bottom) at the edge of the egg crate, solder them up and then cover all of this solder work with the spacer such that looking at the top and bottom edge of the completed panel, you don't see any of this solder work?
Thanks,
Paul
Somehow I understand this but it is very confusing and I have never found any discussions of this or it being mentioned. jer[/QUOTE]
On the web, I found a list of dielectirc constants of different materiels. Of all the ones discussed, urethane has the highest value. Does this mean that heavy build magnet wire with out kinar or teflon or... would be best.
Also I was wondering about the termination of the wires on the egg crate.
Do you cut the wires (top and bottom) at the edge of the egg crate, solder them up and then cover all of this solder work with the spacer such that looking at the top and bottom edge of the completed panel, you don't see any of this solder work?
Thanks,
Paul
Do you mean something like this?
although this is a poor and sloppy example this technique could be used to easily create segmented panel connections and once satisfied tucked in and capped off so that it can't be seen.
As far as the wire insulation goes I would probably have to agree.
But you have weigh out the differences by taking in cosideration of how much voltage you plan on using.
I don't know exactly how much of a difference it would make as this is some thing I had planned on investigating,but haven't gotten that far yet.
If the difference is only a few points it might not be that big of deal.
But if the difference is 2 to 5 or even say 10 times or more this could play a big part as far as efficiancy vs drive and bias voltage levels are concerned.
The way it seems to me is that the slight defficiantcy in dielectric constant can be compensated with a higher drive and bias level unless the constant is quite alot higher,then that could play a big part as far as voltage requirements , again I may be wrong about this.
For instance I'm running 7.5kv bias with a .060 d/s spacing now.
If my dielectric constant was much higher then I would probably not need as much voltage to get what I am getting now as far as effeciancy.
But if I were able to have that high value of constant and maintain my 7.5kv or more of bais I'm sure the difference would be phenomenal.
Thats just my opinion.
This is a study that really needs to be investigated to further extent. jer
although this is a poor and sloppy example this technique could be used to easily create segmented panel connections and once satisfied tucked in and capped off so that it can't be seen.
As far as the wire insulation goes I would probably have to agree.
But you have weigh out the differences by taking in cosideration of how much voltage you plan on using.
I don't know exactly how much of a difference it would make as this is some thing I had planned on investigating,but haven't gotten that far yet.
If the difference is only a few points it might not be that big of deal.
But if the difference is 2 to 5 or even say 10 times or more this could play a big part as far as efficiancy vs drive and bias voltage levels are concerned.
The way it seems to me is that the slight defficiantcy in dielectric constant can be compensated with a higher drive and bias level unless the constant is quite alot higher,then that could play a big part as far as voltage requirements , again I may be wrong about this.
For instance I'm running 7.5kv bias with a .060 d/s spacing now.
If my dielectric constant was much higher then I would probably not need as much voltage to get what I am getting now as far as effeciancy.
But if I were able to have that high value of constant and maintain my 7.5kv or more of bais I'm sure the difference would be phenomenal.
Thats just my opinion.
This is a study that really needs to be investigated to further extent. jer
Attachments
Paul: you can have a look at this regarding the dielectric choice.
http://www.integracoustics.com/MUG/MUG/tweaks/acoustat/technology.pdf
you may find a number of interesting things here at MUG
Acoustat Tweaks
http://www.integracoustics.com/MUG/MUG/tweaks/acoustat/technology.pdf
you may find a number of interesting things here at MUG
Acoustat Tweaks