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Note from Ben Peters, Audiostatic

WARNING: Audiostatic electrostatic loudspeakers are rather complicated products, of which all parts have been carefully designed and matched to each other to form one inseparable unit. Dismantling, taking apart or replacing of parts with non original items easily can end in a disaster. One will also forfeit all rights on warranty and afterwarranty parts replacement at costing price. Building your own electrostatic loudspeakers from scratch or rebuilding excisting factory made products can be a challenging hobby but we strongly advice to think it over before you start.

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Notes, March 21, 1999

Mark, Brian and I are currently rebuilding a set of ES100 (E100 series) AudioStatic's. We have the stators and entire ESL broken down. Here is what we now know about this great ESL by Peter's. I will have pics soon.

The unit is a wire stator construction that can handle about 120 watts, at least that is about the most I can push them using Hafler 3000 which push 150 watt per channel. The frame is black and has a cut frame which the MDF (modified fiber board) rests in. The power supply rests in the lower unit. If you have ever looked at a AudioStatic or visit their web site you know what I am talking about.

The stators are about 14 inches wide and are copper 18 gauge (some where around 3 millimeter diameter). They are string tightly (I am guessing about 3-5 pounds). It looks like they used wire clamps or a machine to pull them. But since they are built of copper, the tension is not great. Running perpendicular are 1/8 inch by 1/8 inch aluminum stock supports the wires, spaced about 4 inches apart. This gives the wire some ability to produce some bass, which it does all right in.

I tried to build a set and I can not get it tight enough. I think the wire is twisted and not straight enough. I think I am going to buy some 14 gauge copper wire and build a better pulling jig. It is difficult to make stators in wire.

We are going to rebuild the current system, but the next version will use perforated sheet steel. Mark found some, a sheet was $30.00 and he says we can get 3 speakers out of one.

The diaphragm is Mylenex 329, 0.5 millimeter. We had to buy 1,800 feet of it cause the distributor does not sell it in lesser quantity. We joked that we could wrap the whole house in it! We have copper tape, mesh type for the main conductor material to polarize the Mylenex The Mylenex is the same as Mylar, it is used for labels and has a high tension strength. Go to the Dupont web site to review there products.

We are using graphite, but are considering wall paper glue (methyl cellulose) as the diaphragm conductor. We also are experimenting using linseed oil and graphite to make a paste. Then applying is to the diaphragm in the usual manner. This is less messy, but I have to evaluate the process better. The oil is not easy to remove, and I am concerned on the life of the oil against the diaphragm.

The MDF we bought, got a sheet of it for $50.00 or so. You can make lots of panels with a sheet, and again the distributor would not sell anything less. The MDF is 1/8 inch in thickness, and we have something a little thicker.

The power supply we have ripped out and a friend helped in duplicating the entire power unit. Basically it is (2) step up transformers which power the stators The ratio I am not sure of but the construction is poor. The trantor 9 volt to 220 volt and then through some capacitors is week too. We are rebuilding the entire unit, to accept 110 volt house current.

I will have the pics out soon. We have some funny photos of the entire lab we have set up. The panels, and how the one unit came apart, and more.

Sean Bowes

History of an Audio Sound

Here is a rough draft of my next update for the AudioStatic repair project. I should have a finished copy with picutures sometime this during mid April

Audio is a remarkable passion of mine. Since I first heard Electrostatic Panels, I have always walked away with the greatest feeling. It is the sound that drives you

My first pair where a set of used Electrostatic custom built by a friend of mine, the guy who introduced me to them. I can remember walking into the main living room of this spare home he used, and seeing a 20inch woofer and two wide and tall ESLs. The system was powered by tube amps, huge mono blocked amps that powered each panel. A tube pre-amp drove it, the sound was better then anything I ever had seen. I can recall my brother grooving around the room, carefully mind you. And we sat there and listened for about 4 hours to all sorts of music.

I knew that panels where for me, but the cost was too much for me. I was young, but saved. And when I was 25 I bought my first pair. I bought those exact panels from that guy. His name is "E", and used to play with ELO, and all those way out synth. bands of the 70's.

About 2 years later I burned up one tube amp, I was seriously depressed. The main drive tube burnt out, the socket over heated, and wiring would need to be done. I thought for weeks

I decided to buy a new pair and also a used pair. I choose the AudioStatic ES100 and a used pair of Acoustats. I choose the AudioStatics because the maintenance issue. See tube amps need a lot of care. You need to have them built, then tuned. And if they are new tubes then expect to retune in about a year. AudioStatics use a DCI interface, which is more of a solid state sound. Cheaper to maintain, but less quality in sound. How much less. Not much - you would never hear the difference unless you paired them up to a tube system.

And then if you go tubes you can always remove the DCI interface and go direct to the ESL. I actually believe the AudioStatics would sound better on a tube system. I want to built a direct tube system someday.

My brother bought a pair of AudioStatics, and another friend of mine owns a pair as well.

How I got to this project

I blew out my right channel AudioStatics, and I was depressed again. How could I have possibly gone through two pair of panels you might ask. The tubes burnt up do to excessive power and overheat. The AudioStatics burnt out due to too much power on the input voltage through the "Cockroft-Walton" voltage generator. One, if not several of the step up capacitors burnt out. See the input voltage from the Trifo transformer had placed the input voltage to 330+ volts. The capacitors, which use a Philips 330 0.047mF cap are only rated for 250volts. So it was only a matter of time. The input transformer, the type that plugs into the 110volt wall outlet makes 13+ AC volts. The DCI unit comes with a 9v:220v Trafo. Do the math.

Maybe I got the wrong transformers? Maybe? All I know is that I had another bad unit.

I looked everywhere for someone to fix them. I did not find anyone. So I decided that I would research and redesign the entire system. What knowledge did I start with. Very little. I had some electronic experience, and even took a few courses in college. What could I lose?

So I read two books. Read over another electronics book on voltage and audio system. Asked anyone who I know into high end audio tons of questions. Consulted with a several friends who build audio system for the military here in the US. And had a lot of equipment to utilize. This project has consumed my life for the last 2 months. Where are we at?

Finished.

Yes. But research and time can cost a lot. I tried to keep this project under a budget. I wanted to build the entire panel within reason. The research and development has cost me over $500 so far. I still use a lot of equipment from friends too. The oscilloscope, high voltage probes, and impedance testers just do not come by every day. Will you need this equipment? Yes, if you plan to give it your best shot.

How much will it cost you to build in the end? About $800-$1000 for something close to an AudioStatic. What costs the most?

  • High end transformers (ones with multiple primary and secondary "Litz" windings)
  • High end caps (Infini, Blacks, etc.)

Those alone could go for around $500 US dollars per panel.

Panel material

  • 3/8" MFD (modified fiber board)
  • 0.5micron #339 Mylenex (similar to Mylar and made by Dupont)
  • Conductive Paint comes in a pen
  • Copper Tape (3M brand) Double Back Tape (3M brand)
  • Graphite (small and fine grain)
  • Silicon Caulk

    Description of the panel materials

MFD (modified fiber board)

The MDF came from a small plastic distributor in South Jersey (USA). He sold use a sheet for about $50 US dollars. He had some other sizes and thickness, but we wanted it to as exact as possible to the AudioStatic's MDF.

Mylenex

The Mylenex is like Mylar, and is made by Dupont. We used the #339 type. You can see the specs on the Dupont web site , which states that the Mylenex is used for labels, and is printable on one side. This we got it for free. Can you believe it? We went in and said we needed a sample. They gave use about 1,000feet of it on a roll 36inches wide. I could wrap the whole house with it. It works great, and might be better then Mylar in some respects. It is more industrial in quality then the Mylar and has the adhesive feature which allows us to use double back tape instead of glue.

Conductive paint

You are going have to create a trace up the diaphragm about 3mm from the edge of the MDF. This will provide for electricity to reach the panel efficiently. You are then going to sandwich the conductive paint to the copper tape.

Copper Tape

The copper tape is from 3M and comes in 32feet rolls. It costs about $35 US dollars. We got this for free too. It is a mesh copper tape, that does NOT have glue on it at all. We sandwich it in between the MDF to make contact with the Mylenex and solder a wire lead to it. It works great, but I am not sure if we can get more of it for free. We are looking into aluminum tape, which we have a lot of. The problem with aluminum tape is that it is like foil, and can break and is not easy to handle. I have not considered another material yet, so we continue to use the tape. I want to try conductive paint next. I think it is a better choice when working on the Mylar and the panel needs it since you really need to run the power all the way up the panel. I will explain why you need to do this later in the notes below.

Double Back Tape

The double back tape is from 3M too. We bought it from Home Depot, which is a huge warehouse for home supplies here in the US. I mean they got everything you can think of. The tape cost around $3 US dollars.

Graphite

The graphite we had, in a small 2-pint can. I got it from my dad who used to work for the Navy. It is very fine graphite, and is not that messy. I have some other types of graphite, but they are not as good as this. I have a can of copper and graphite in linseed oil base too. We have not used that, but have considered it. We are also looking into Methylcellulose, which is wallpaper glue. I have looked into this but we have not gotten around to it yet. See we need an oscilloscope to measure down to the meager-ohm to see if it will work. And the guy that has one (actually he has three of them) has them packed away in storage since he is moving. So when he gets settled we will try it. As for not the graphite works good, and is not that messy.

Silicon Caulk

We got a tube of it from Home Depot for about $4 US dollars. It is used to space the diaphragm from the wire starters. The diaphragm has a small drop on it under the rods. Sorry I do not have the exact pictures, but later in this document I will provide some drawings of how this is used as well as those items I have listed.

Stator Material

  • 18AWG Wire
  • Aluminum Square Stock
  • Finishing Nails
  • Epoxy (3M type)
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18AWG Wire

18AWG wire was difficult to find. Since the AudioStatic's use this type of wire, which is about 3mm thick or so, we had to find it. And we did find it, except it had PVC coating on it and the epoxy would not stick to it. This was a painful experience. We had to run a razor down the wire and remove the coating to get to the primary insulation on the wire. After cutting off about 500 feet or so we were ready. We made a "jig" that ran the wire through and the razor cut the PVC into half. Then we rewound the wire back onto the spindle (you'll need an extra empty spindle for this). The "jig" merely holds the wire in place so that the razor can cut it.

Aluminum Square Stock

Aluminum square stock we got from Home Depot. It is probably the most costly thing on the whole project next to the power supplies. We used 1/4 inch x 1/4 inch square stock, and you need about 180 inches of it. It comes in 32 inch lengths. I think we used 4-5 bars of it. It costs around $3-4 US dollars. We used bolt cutters to cut it to the 8 inch length. These rods are used to support the wire at 8 inch intervals.

Finishing Nails

Finishing nails came from Home Depot too. We bought a box for about $1 US dollars. It is slightly less then the thickness of the wire. The thickness is not important. When you actually go and layout the stator, you position the nails so that they are off-centered in a "zigzag" pattern. So that winding the wire is easier and can be as close as you want. I will explain this later on and how we built the stretching jig for the wire starters.

Epoxy

Well we got this for free too. And we got a whole case of it. This epoxy is great. It sets in 15 minutes and hardens in 20minutes. We have a special gun and it has a mixing tube off the end that mixes the hardener and resin together. I think the gun is the best thing we got going. We do not use it often since we use the double back tape to hold the MDF and Mylenex together. But when making MDF frames and gluing the rods to the wire it is great. The gun and glue must cost about $100 US dollars. I think that contact adhesive would be just as good. Contact adhesive is used to glue industrial tile to the floor, or to glue Formica to a wood surface. The only problem is that it sets up fast and you need a lot of ventilation. It might work, but try and find a good epoxy.

Power Unit

This is for one unit. The plans and the specs here are not exact. So you better know what you are doing. I merely am trying to explain how to replicate the Audiostatic power unit that produces about 7,000+ volts. This is high power. So please do not try to build this unit if you are not capable of doing so. Ask someone to help you, or buy one. Audiostatic might sell you the power unit. They call them DCI interfaces. I think the unit might go for about $400 or more US dollars. I know that you can not get them here in the US, you will have to go through a dealer in the UK or somewhere in Europe. Please, be careful.

I am still building the power unit so these specs are not complete yet. I will have more on the layout later. Here are the parts.

  • 40 - 47k ohm 5%+/- tolerance resistors (about 1 watt should do - or you could go for a 2 watt).
  • 1 - 10 meg ohm 5%+/- tolerance resistor (about 2 watt should do it).
  • 1 - 4.7 ohm 5%+/- 10 watt (ceramic type)
  • 20 -1N4007 diodes
  • 19 Philips model 330 0.047um 250 volt capacitors (You could use the Mallory or Sprague Orange Drop type)
  • 2 - 1:75 transformers (I will explain these in details later)
  • 1 - 110volt:220volt AC step-up transformer (The original power unit used a Trafo 9volt:220volt step-up. I am replacing it with 110volt input. More on this later too).
  • 1 - 33um 5%+/- tolerance 250volt non-polarizing electrolytic capacitor
  • 1 - 6inch x 10inch piece of MDF to mount the components on.
  • 1 - 10 foot piece of teflon coated 24AWG wire (to create the tracing for the circuit).

Building the circuit board

To build this power supply you will have to first drill out the MDF to create the same circuit. Try to use the same size board as I have described below in picture 1. If you create a smaller board the voltage may drop due to shunting of power. After you drill out all the wholes begin to mount all of the parts as a dry run, to allow you to visually see how the circuit will go together.

Figure 1

You can etch a board out, but the etching kits are small. Which means you will have to use two boards glued together which is okay. It is faster and cleaner to use a printed board. No wire connectors, no bad solder joints, and need I go on. Etching is easy. The pen method is okay, the exposure technique is good too. I find the sticker method the best. Simply apply the connection paths out on a board and roll hard has hell to make sure the plastic contact paths are set, and carefully dip it in the solution.

The drilling is best on a drill press machine. Now place that aside. We have more work to do.

Transformers

We are going to need three total transformers. One which will power the system, and two which are used to power the stators

Main power transformer

You are going to have to find a step-up transformer which will be used to power the unit. In the original system, you plugged in a small power transformer into the wall, which converted 110volts down to 12volts AC current. The power then went into the system, into the Trafo with 12volt which stepped up to 220volts+. I am not sure why they did it this way, but I have some idea. It could be that they did not want to build a voltage regulator to create 12volts of continuous power. Another thing is that the Trafo is rated for 9volts, but they are sending in 12volts. Trafo transformers come from Germany I think and are known for wide impedance. Meaning they turn 9volts into 220volts which is great. The next system I build I am going to use a 110volt to 220volt power supply. I got one from Radio Shack and took it apart and mounted it into the new case I built for the power supply. The step-up transformer cost about $30 US dollars. I am assuming that the power supply does some cleaning of the power to some degree. I mean that the power coming from the Power Company is not a perfect sine wave, so try and find one that helps filter the power and produces clean power. I have seen simple step-up power units for $15 US dollars.

Stator power transformers

The strator transformers, there are two of them, have a 1 to 75 turn ratio. So this means if you use a 300watt power amp at 8ohms, the output current from it will step up the power to about 7,000+ volts (give or take a few volts). A 300watt power amp produces about 100volts. Now I have heard of guys taking a small Radio Shack transformer, pull off the secondary winding, then count the primary winding, then wind back onto the transformer the proper ratio to create the 1 to 75 ratio. This can be done. However the sound may be poor in some regards.

I do not recommend a "Litz" wire on the secondary either for beginner winders. However it is easier to wind with, it costs more. And you do not want to make mistakes like snapping the wire. If you do, then dip the leads into a solder pot and allow them to sit out of the windings. Remember this, "Litz" wire can not be soldered on the core. It must be done outside of the core.

What do I prefer. A "Litz" on the secondary. I have seen Amplimo AudioTransformers might be a better choice or the . They only cost about $125 dollars for the good one and about $90dollars for the okay ones. I am going to try out a pair of Sowter which I am ordering this week. I am still winding my own too. I want to compare the sound.

How do you wind your own transformers ? You need the following:

  • A sewing machine motor
  • A block which looks like the one below
  • A mounting vise made out of wood like the one below
  • A oscilloscope to read the frequency from tone generations
  • A computer to generate tones and record them for play back

What you need to do is this.

  • Primary Winding Wire: A spool of 24mil magnet wire for the primary
  • Secondary Winding Wire: A spool of 34mil magnet wire for the secondary A spool of 34mil Litz wire for the secondary
  • Cardboard: Heat proof tape (looks like thin plastic tape but made for taping winding layers) 3mil Mylar

Transformer specs:

1 layer on primary, 65 turns 30 layers on secondary, turns 160

This is going to be a real good exercise in Audio Technology.

Figure 2

  1. Okay first build the stand like the one shown in figure 2. How does the wire get onto the core? As you power the Sewing Machine Motor, the wire will travel onto the core, using some tension in the process. After you reach a said width you can almost guess that the correct number of turns have gone onto the core. You can do this. Or you may want to build a small hand turning device to wind the wire back on. What do I recommend? Wind it back on with a Sewing Machine Motor or Hand Drill can be substituted, but carefully counting the layers. The hand method will take you a long time.
    To do this, you'll need some wire that is used to wind transformers. I have a friend that winds professionally so I get the wire for free. You'll have to find it yourself, sorry. Consider trying to find a 20mil magnet copper wire. I had my transformers made by my friend; however the next time I am going to make them myself using the method I describe below. Now we start with raw materials, and do not cheat like the Radio Shack method I mentioned above.
  2. The center core is first made of paper cardboard. First cut out a rectangle about 2inches by 8inches. Now make a small tube out of it, and then square out the tube to form an inner square which will mount onto the stand. This is called the "block" which is made of wood. Tape it. This is a core. If you are not sure, take one apart and you'll see what I mean. The core is where you are going to wrap on the primary winding first. The core has an inner square dimension of about 2inches by 2inches.
  3. I want to stress the importance of being very careful when winding. You will snap the wire easily, it is like hair.
  4. Place the wire to the left and wind to the right. The beginning of the wire will hang out the left side and the end of the wire will hang out the right side. Make one layer. You are going to lay on 65 turns, with one total layer on the primary winding. Only one layer! Prior to finishing the first layer, attach a small piece of "shrink" tube over the wires. This will give it support that you will need later when you solder a lead onto it. I usually leave off about 4inches and put a small piece of tube over it, then begin the secondary layer. Do NOT apply heat to shrink the tubing, wait until you are finished. After winding on the layer, you'll need some tape to hold the layer onto the core. I use a special heat resistant tape. I think you can find something in the "Newark Electronics" catalog which can be used to hold down the layers. At any rate you are going to need something to hold each layer down.
  5. Next place a piece of Mylar over the layer.
  6. Now you have just completed one layer which is called the primary winding.
  7. Now you are ready to start the secondary winding.
  8. NOTE: On the AudioStatic transformer, it appears that the secondary winding uses a "Litz" style wire. What is a "Litz" wire? It is used to prevent skinning on the wire as you reach high frequencies and reach very high voltages. This is what a "Litz" wire will prevent. See at high frequency, the electrons travel on the outer portion of the wire, not through the whole wire. This is called a "skin" affect. You then loose signal, which could occur when you send in a high frequency into the main amps which then go through the step-up transformers. Could it happen? Yes. Will you hear the difference? Probably. Can you measure it? Yes. How can you measure it? I use a computer which can generate exact tones to see the response of the transformer. I am not going to get into this because we could go on for hours. I mean if you were that concerned then you would be running "Litz" wire through the whole system. Right? Do I use "Litz" wire on my stereo system? Yes.
  9. Use Cool Edit 96 to create tones.
  10. You send out a signal from the computer to the primary winding and evaluate it on the oscilloscope.
  11. By now you have place on XXX layers which is the primary winding. Test the winding with an ohm meter. This will prove that there are no breaks in the winding.
  12. If you have "Litz" wire to create the secondary then use it. You can run wire in parallel as well to create the "Litz" secondary.
  13. To wind the secondary side we are going to do the same thing as we did above. Winding the wire and making layers. You are going to put on XXX per layer with a total of XXX layers. Do not forget to put on the "shrink" tube over the wire before the first secondary layer.
  14. If you snap the "Litz" wire, you will need to bring out the wire from the core. Then use a solder pot to dip the wire. Use a plastic sleeve over the wires so that they are insulated.
  15. Okay, now we are done making the core. Test the wires one more time to make sure it is intact.
  16. Now we need to mount the transformer into an "E" and "I" metal frame. These you'll will have to find too. Sorry. You might be able to get them from Mouser or Newark Electronics. The "E" is going to go through the core in opposite fashion. One overlapping the other with the "E"'s facing eachother. Now slide in the "I"'s where the "E" was not complete on the ends. Finish with the mounting bolts which will complete the full "E" and "I" construction.
  17. Now you are going to have to place the transformers in to an oven. Bake them to dry them out, at low heat. Then dip them into a transformer shellac. Place them back into the over to dry.

Okay, that took I am sure several weeks to do. Or maybe a day if you have a friend like mine. Or maybe less if you bought the transformers.

Update June 2, 1999

What have I been up to these days? I just moved into a new house, so as you probably have experience - everything is everywhere. I still have to set up the shop, but have been using 2 of my buddies, who are into high end audio, shops. I have re-built the Audio Static panels completely, and can replicate them. Peter's design is flawless!

My next project is to mod out the tubes with better tubes, I hate those 6HB5's! Then I am going to build 8-Audio Static panels. Four on one side and four on another. Each side with their own set of panels. Next finish mod'ing the last pair of Acoustat tubes, then power them in another set of Audio Static design panels.

Finish the system, with a complete surround sound system. Eight Audio Static panels in front, and eight in the back. In a small hall like room, with sound baffles. Hell, even a million dollar system could not beat it.

Anyway, now you know where I am at. I am sorry no pics yet. I have been waiting on a Mavica but I may be able to get some shots in on a 8mm cam and scan them over using my video card interface. But with the new house, and working things are rough! Thanks again. You guys gave me the thought and passion which I have come to fully understand.

Remember it is high voltage. I had 3 mentors that helped me design and build this. Which I am sure you do not have. So be careful and find an audio engineer. Lockheed has the best audio engineers these days. Who else can build the best equipment, but the US government.