Jack Sutton's (XEN) Plans for an ESL
A common mistake people make when auditioning loudspeakers is to compare them to other loudspeakers. A better reference standard would be to go to live concerts and listen to real musicians without electronic sound reinforcement.
Electrostatic loudspeakers have been with us for nearly seventy years during which time many design variations have come and gone. Early designs suffered from diaphragms that were just too thick to provide extended high frequency response by today's standards. By the 1960's modern plastic films were plentiful making high frequency responses an easily obtainable goal, this led designers to think of ESL's mostly as tweeters. ESL's are far more than just tweeters as you will find out as you read through this manual, they are smooth colorless transducers capable of wide flat response when properly built.
When listening to a fine pair of full range ESL's; you will be drawn to their lifelike naturalness. They have no listening fatigue, but rather a seductive quality that you just can't get enough of .
ESL's are in the minority as far as most audio enthusiasts are concerned and probably always will be.
Planar dipoles need to cover considerable area to do what they do best, so most full range ESL's are on the large side.
Needing to be large precludes the use of ESL's in vehicles or very small rooms such as college dormitories.
Size is not the only factor against the ESL; they require a high voltage supply and matching transformer.
There are only a few commercial manufacturers making ESL systems and they all have a high price tag.
With all the negative publicity against them, there seems to be little reason to bother with these devices at all.
There is a small but savvy group of people in the world who know a good thing when they hear it.
They are people who have listened to real musicians and set their standards by the way live music sounds.
They are people who choose to listen to reproduce music through ESL's.
The planar dipole ESL comes closer to the sound of real music than any other transducer yet made.
ESL's can be built on a kitchen table and will reproduce music of unrivaled high quality.
You are about to enter into that small but savvy group of people, by building a loudspeaker system of incredible sonic detail.
The ESL system described within this manual is of proprietary design and construction techniques; you may build it for your own use only.
The cost is a small fraction of commercially available units.
The electrostatic cell has five basic components, a diaphragm, two stators and two spacers.
All modern ESL's use two stators for true "push pull" operation, one in front of the diaphragm and one behind the diaphragm.
The stators need to be electrically conductive and ventilated in some manner to allow sound to pass through them unencumbered.
The most popular stator design at present is the perforated aluminum system.
This system is easy to fabricate because basically the stator is already built; all the builder need do is determine what size to make it.
The main flaw in this system is when music is playing through these cells certain musical peaks may cause arcing.
When arcing occurs within the cell there will be a momentary collapse of charge, this will produce an annoying drop in sound level to say nothing of possible damage to the cell.
Some suppliers of ESL kits are marketing a type of spark gap to avoid arcing within the cell; this is a crude system with little merit. While this device may save the cell from possible damage, it amounts to putting a crowbar across the output circuit and it still produces the annoying drop in sound level.
XEN has produced a stator design that is completely insulated against arcing, which also greatly reduces shock hazard.
Our insulated cell design has none of the annoying side effects of perforated aluminum.
XEN ESL systems are smoother sounding, more dynamic and have
more octave bass than other kit systems using perforated aluminum.
We admit you can't build a XEN ESL system in one evening, but the extra time it takes is well worth it.
You can poke a hole through a piece of paper with a pin and make a quick and easy lens, but it won't be a very good lens.
We believe the design of the stator to be of utmost importance.
There is no reason to justify using perforated aluminum if terms such as quick and easy are to be headlined as design criteria. This is simply a second rate way to build an ESL.
XEN ESL's are constructed on an easily obtainable plastic material called "egg crate"; available at most home improvement centers.
This material is made conductive by stringing a very small gauge wire up and down the length of the cell going across it's width spaced every tenth of an inch and bonded in place with epoxy.
The dielectric constant of the insulation jacket on the wire is entirely sufficient to thwart high voltage arcing.
Attempts by other designers to use insulated wires bonded to "egg crate" have been tried in the past, yielding compromised results.
XEN has articulated this design by optimizing wire size and combining it with specific cell shape and area, plus use of our laterally displaced spacers and choice of diaphragm film.
Our cell design uses a special foam tape to hold the diaphragm at proper tension, it not only holds the diaphragm but also serves as a spacer between stators. This tape is American made and is not offered by any other ESL kit suppliers.
Xen spacer design is unique in that the spacers are laterally displaced from the stators, this means that the spacers never come in contact with the active portion of the stators.
The dielectric constant of our foam tape is between 200 and 300 volts per mil.
This is an academic specification because our laterally displaced spacers could be made of metal and still not arc.
The foam tape has an excellent adhesive, good uniformity and offers beneficial damping properties for the diaphragm.
Some perforated aluminum designs also use a foam tape spacer, but the tape comes in direct contact with the aluminum.
The main problem with putting spacers directly between stators is stray capacitance; this is useless stator area that produces no output.
All foam tape is porous and can harbor small amounts of humidity, this can manifest itself as a high resistance between stators of perforated aluminum cells.
A high resistance shunt can reduce cell output and alter arc threshold.
XEN ESL's have no stray capacitance and are impervious to foam tape humidity problems. 100% of cell area is used to produce sound.
As you know by now the diaphragm needs to be thin to allow an ESL to produce sufficient high frequency response, it also needs to be electrically conductive.
Some designs use a polyester film with a thin deposition of aluminum on one side, while this works it also adds to the overall mass.
This design also creates low impedance, which is less desirable in terms of constant charge characteristics.
The most widely used method for making a diaphragm conductive is by rubbing graphite into the film material, this is the method XEN uses.
The XEN ESL cell uses a film material made of polyvinylidene chloride, this material is .5 of a mil thick and has more flexibility than polyester for increased bass response.
Use of a special heat gun is unnecessary for tightening the diaphragm, as an ordinary hair dryer will be more than sufficient with this material. (see cell testing)
The XEN high voltage bias supply kit is unusual in both design and component composition.
Our bias supply has very high output impedance at very low current, so it is not possible to measure the bias voltage directly with a standard high voltage probe.
You can however use a standard digital multimeter for adjusting high voltage by monitoring a reference point for bias drive. The XEN bias supply uses a high value resistor coupled at the output to the cells, which will function as part of a low pass filter.
The capacity of the ESL cell system will be the remaining part of the filter, this helps keep noise to a minimum.
There are auto bias devices being marketed by some ESL kit suppliers that supply high voltage bias by converting audio signal voltage from the power amplifier.
These devices are a very poor substitute for a proper high voltage supply, as they usually contain only one component, a high voltage diode.
An ESL cannot operate properly from a half wave rectifier that gets its power from the high side of the ESL's matching transformer.
This system operates poorly because the diode's internal resistance bleeds off the charge on the cell that was initially put on it by an audio peak.
Using such a device skews the dynamic range of the music as the cells charge and discharge, similar to a slow audio expander.
To sum up, these devices usually cost many times more than one high voltage diode.
XEN considers the role of the bias supply to be an important one, beyond the obvious.
Rather than review the basics of ESL theory at this time, let's look at something XEN does that is different from most other designs.
Our ESL system relies on integrating the bias supply and the cells to optimize bass response.
XEN ESL's are tuned to maximize the fundamental bass Q of the diaphragm, by carefully matching the bias supply voltage to the requirements of the diaphragm.
This technique results in producing a full range ESL system capable of smooth extended bass response, that will have many a trained ear looking for that hidden subwoofer.
We're not telling you our ESL system will knock plaster off the walls, because it won't.
Let's be realistic, the laws of physics dictates there is no free lunch.
You can not have wide range frequency response and high volume levels from a full range ESL.
What XEN ESL's offer is incredibly articulate and detailed music reproduction, with wide range and reasonable volume levels.
Because an electrostatic loudspeaker is a high voltage, high impedance device, it requires an audio signal of high driving voltage.
A simplistic but exotic approach taken by one company involves use of a differential high voltage source controlled by a high voltage opto-isolator.
In the past ESL's were directly driven by tubes, usually triodes meant for high voltage regulators in tube type TV sets.
The most practical and widely used approach is the matching transformer, also used by XEN.
Most power amplifiers have output voltages on the average of 100 volts peak; this is not nearly enough to run an ESL, hence the use of a matching transformer.
XEN uses a transformer with 150:1 turns ratio, 100 volts from an amplifier output produces 15,000 volts for the ESL.
We talked about stray capacitance in the "Stator" section, now you will see why it becomes important in the design of an ESL cell.
The capacitance of the ESL as seen by the power amplifier is the turn's ratio of the transformer squared, times the actual capacitance of the ESL cell system.
The XEN ESL cell is 160 picofarads, two of these cells are used to make one ESL speaker, that's 160 x 2 = 320 picofarads.
Converting to microfarads = .00032, this is not a lot of capacitance if the power amplifier had only this to drive.
Here is what really happens, .00032 mfd x 150 squared = 7.2 mfd.
If each cell had an extra 40 picofarads of "stray capacitance", you would have
.0004 mfd x 150 squared = 9.0mfd load on the power amplifier.
Fortunately XEN ESL's have no stray capacitance.
An ESL must be equalized to sound right; otherwise it will have a bright shrill sound. This is because it's impedance keeps increasing as frequency decreases.
ESL's should not be passively equalized at the amplifier output because high frequency headroom would be absorbed and wasted.
XEN ESL's have a large Q factor at bass frequencies; if unequalized they appear to have a response dip at middle frequencies.
XEN uses a gain compensated passive equalizer, of first order asymmetrical bandpass characteristics.
This means that the amplifier doesn't have to work as hard at frequency extremes, reducing the possibility of distortion.
The result of this equalization is an ESL cell with virtually flat response across the full range of audio frequencies.
Two of the main complaints raised against the ESL have been, lack of bass and lack of high volume.
A XEN ESL system will produce maximum peak volume levels of around 101 decibels, with bass extending to about 35 hertz.
While this is not rafter shaking bass or ear splitting volume, it is realistic for a wide range of musical tastes.
When listening to a pair of XEN 's you will hear plenty of deep satisfying bass, you just won't feel much of it.
ESL's tend to be room friendly, because they do not excite as many room nodes the way boxed speakers do.
XEN ESL's use two 4 x 36-inch cells stacked on top of each other.
Whether you're sitting or standing the music is always at ear level.
The cells are mounted to a unique folding flat baffle covering 25 square feet providing true dipole operation, as well as true line source benefits.
Our four-inch cell width allows for increased horizontal dispersion, which helps widen the sweet spot area.
Xen ESL's have a cell area equivalent to three 12" conventional speakers per channel.
The crowning glory of a XEN ESL stereo system is it's imaging, since all sound comes from a single source diaphragm for complete phase coherency.
No separate high or low frequency cells - no crossover networks.
XEN ESL's have marvelous musical detail, a truly colorless neutral sound that will reward your ears with hour upon hour of listening enjoyment.
The following list comprises all of the materials necessary to construct four XEN ESL cells; (four are needed for a stereo pair).
1. Three sheets of "egg crate", 2' x 4' plastic grid, used with light fixtures in
"dropped ceiling" installations .
2. 25' of polyvinylidene chloride film (available through XEN) DO NOT SUBSTITUTE!!!
3. 108' x 1" foam tape, (available through XEN) DO NOT SUBSTITUTE!!!
4. 1200' insulated stator wire, (available through XEN) DO NOT SUBSTITUTE!!!
5. Combined 9 ounces of two hour epoxy resin.
6. 400 nylon wire ties 1/10" x 4", (available through XEN)
When purchasing multiples of "egg crate", stack all sheets on top of each other and make sure the grid patterns line up perfectly.
The reasons for this is that there are variations in specifications among different manufacturers, try to make sure all your material is from the same manufacturer.
If you wind up with mismatched material the cell will most likely go together all right and operate fine, but the grid pattern will fall out of register between the two stators.
It's always best to keep organized when tackling any project, so let's go over a few things first.
1. Assortment of hand tools
2. Finely powdered graphite
3. Utility knife
4. 22 x 44 x .25 inch glass (or larger) with rounded edges
5. Masking tape
6. White paper or poster board 8 x 40 inches
7. Cotton balls
8. Surgical gloves
9. Window cleaner
10. Pencil or pen
11. Paper towels
12. Single edge razor blade
13. Hair dryer (never use a heat gun on these cells)
14. Paper punch
15. Aluminum foil
16. Electric or cordless drill with, 1/8" bit, 5/16" bit
17. Work gloves
18. Soldering iron
19. Hot glue gun
20. Wire strippers
21. One pound bag of #18 rubber bands
22. Six 1/4" bolts two inches long with matching nuts and washers
23. Piece of plywood 3/4" x 12" x 36"
24. One-ounce plastic mixing cups for epoxy resin (hobby store)
25. Waxed paper
26. Two packs of thumb tacks
27. Cotton swabs
28. Vacuum cleaner with brush attachment
29. One dozen 4-40 machine screws
30. Two dozen 4-40 nuts
31. Two dozen # 4 flat washers
32. Nail polish
NOTE: The grid structure of "egg crate" is wedge shaped, keep the thicker side up, this will always be your construction surface. (Unless otherwise noted)
READ THROUGH THIS MANUAL FIRST
1. Lay a full piece of "egg crate" on a work surface, you will notice every 10 grid squares in both vertical and horizontal directions has a raised tip, carefully cut these tips down smooth with the rest of the surface using a single edge razor blade.
2. Using a pair of diagonal cutters, cut away the thin rail of plastic around the periphery of the "egg crate", it should then have 1/2" spikes going all around it.
3. Put on a pair of work gloves and start pushing on these spikes with your thumb close to the base to break them off, use a continuous motion right straight through like toppling dominoes.
This technique breaks the spikes off close to the flat surface, which will be more finely finished later.
4. Hold the piece of "egg crate" up vertically and count across from the upper left-hand corner 12-grid squares.
With the diagonal cutters start at the top and cut through each horizontal grid working your way to the bottom, make these cuts close to the left of the vertical grid.
Break off the spikes, as before, you should now have a piece of material 11 grid squares wide by 80 grid squares long. MAKE SURE BEFORE YOU CUT !!!!
5. Count down 64 grid squares and cut across the top of the next horizontal grid, break off the spikes as before.
You should now have the final stator size of 11 grid squares by 63 grid squares
(approximately 6 9/16" x 37 1/2") , actual diaphragm area will be closer to 4" x 36", because of laterally displaced spacers .
6. Use a rasp file and sandpaper all around the edges of the stator to remove all traces of the spikes and make the surface look and feel smooth.
7. Make seven more of these stators as directed above.
8. Position a stator on a work surface horizontally thick side up, find the lower left grid square and drill an 1/8" hole through the side facing you (the long side).
Continue drilling to the back wall of this same grid square. (2 holes in line)
A wire will be passed through the rear hole later.
9. Count 31 grid squares to the right (including the ones you just drilled), at the 31st Grid Square, drill another 1/8" hole. (Only one here)
(All stators are drilled the same for compatibility)
10.Lay a drilled stator down on a work surface horizontally, with drill holes to the left and thick side up. Unwind a few inches of stator wire and tie the end around a nylon wire tie, leaving three inches for a connection later on.
11. Place the "eye" end of the wire tie down through the lower left grid square of the third row and loop it up to the left to encompass the edge rail of the stator, do not pull it completely tight, leave a small loop that almost touches the right side of that grid square.
12. Run the wire down to the right side of the stator being careful not to kink it.
At the lower right grid square third row place a wire tie down through it "eye" end first.
Before closing the loop to encompass the right edge of the stator rail, place the wire in the loop so the spool end can turn up and to the left to make it's return to the left side of the stator.
Close the loop and adjust it so that it almost touches the left side of that grid square.
Keep lacing the wire back and forth across the width of the stator in this manor, pulling the slack out of the wire as you go along, but not so much as to cause bowing in the stator. Later on the wire ties will be adjusted to pull the wires tight, but not yet.
13. You will be using 3 wire ties at each end of each grid square row, allowing 6 wires per row.
NOTE: The beginning row (third) and final row (ninth) will only have 5 wires, the total number of wires in each stator will be 40 wires .You will be covering 7 continuous grid square rows with wire, starting with the third row and ending with the ninth row.
This leaves a blank perimeter all around the stator, one row of grid squares on each end and two rows of grid squares on each long side for placing spacers later on.
14. When you have finished lacing the wire, you should only have 2 loops of wire ties on the right side of the stator's ninth grid square row.
Tie off the 40th wire on the left side in the same manner as the very first wire, leaving two or three inches for termination.
15. Locate 3/4" x 12" x 36" plywood to serve as a bonding jig and place on a work
Surface; place a stator that has not been strung with wire on top of the plywood as a temporary template.
16. Line up the stator on top of the plywood as to allow an even amount of hang over from left end to right end, mark drilling holes at the four corners of the plywood down through the appropriate grid squares (first grid square row and eleventh).
17. Locate the approximate center of the stator (around grid square #31) at the first and eleventh grid square row and mark drilling holes, drill all holes with a 5/16" bit.
18. Locate the stator with the wire strung on it and mount it to the plywood with a length of waxed paper under it nut side up using the 1/4" bolts, nuts and washers.
19. Finger tightens the nuts, gently, as not to crack the plastic.
20. Starting on the left side of the stator, start tightening the nylon wire ties not more than half way through the middle of the grid squares.
Do the same on the right side of the stator, then check for even spacing of the wires from left to right and make certain the wires are not crossed over each other, especially near the ends.
Run your eye along the stretched rows of wires to check for valleys where the wire is not touching the edges of grid squares.
21. In areas where the wire is not touching the grid, stretch rubber bands across the narrow portion of the stator.
Position the rubber bands so they lay across the middle of the grid squares and fasten them with thumbtacks pushed into the plywood. (Don't get epoxy on the rubber bands)
22. Uses a nylon wire ties to mix epoxy in a plastic cup, a drop from each part about 3/4" in diameter and mix for one minute.
Before bonding the wires you may wish to consider erecting a simple bridge to steady your hand while applying the epoxy resin.
All you need do is cut a piece of scrap plywood 6" x 15" and nail it over the edges of two 6" pieces of 2" x 4".
Lay this bridge across the stator, starting at one end and moving toward the other end as your work progresses.
Right-handed persons should start on the left and work to the right and vice versa.
23. Once you have mixed the epoxy use the wire tie as your applicator.
Apply it with repeated strokes across the rows of wires, starting with the row nearest the wire tie loops.
Work as quickly as you can but be careful not to allow the epoxy to run down the sides of the grid squares, conversely make sure each wire is getting plenty of resin without building the surface too high, you will learn to judge as you go along.
Do as many rows as you can before the resin stiffens and becomes hard to work with, when this happens mix a new batch with a new mixing cup and new wire tie.
You may be able to do as many as 10 rows per batch, enabling you to finish a stator in less than an hour.
24. Let the stator sit in the bonding jig for 24 hours to make sure the epoxy is cured.
To expedite matters you may wish to consider building several more bonding jigs.
25. When the epoxy has cured, release the stator from the bonding jig, carefully cut all of the wire ties as not to damage or pull loose the newly bonded wire and discard.
We are now ready to surface the diaphragm film with graphite.
26. Locate white paper or poster board 8 x 40 inches and lay it on a work surface.
Lay a stator over the paper and center it by eye, using a pencil or pen trace a line on the outer perimeter of the stator and set the stator aside.
Using a yardstick and or a straight edge, trace a 4" x 36" rectangle border inside the previous rectangle. When centered up, there will be a 1/2" margin on the ends and 1 1/4" on the long sides.
27. Locate the stator you used as a template in #26 and lay it down on the paper (thick side down), hole end to your left and lined up with the pencil outline, designate that end of the paper to be the one to orient the holes to. Counting from the left draw a line across the long 1 1/4" border nearest you at the left edge of grid square # 30, then draw a line at the right side of grid square # 32 Finally, draw lines to the left and right of grid square #31.
You should now have a section of that border that centers up with grid square # 31 that matches up with the drilled hole on the stator for the bias connection.
The reason for drawing this area is because it defines the section where the diaphragm bias connection will be when you apply graphite to the film.
No graphite is applied to the outer perimeter (border area) of the diaphragm except for the bias connection to insure absolute adhesion to the foam tape spacer. (Graphite lubricates)
28. Set the stator aside and center the drawing you just made face down on a piece of glass and tape it down on four sides.
Turn the glass over on to your work surface and clean it with glass cleaner.
29. Put surgical gloves and cut a piece of polyvinylidene chloride film 11.5" x 44".
30. Lay the film on the glass and center it over the lines on the paper. Using just a slight pull, stretch it out holding it with masking tape at the corners first. Then through the middle on opposite sides and in between the previously taped areas until the wrinkles are gone. Don't stretch it too tight, it's very important to keep the fundamental diaphragm resonance from going too high.
You can heat shrink it later with a hair dryer if needed. (See cell testing)
31. Continue wearing gloves if you would rather keep graphite off your fingers, sprinkle a small amount of graphite in several spots down the center of the diaphragm area, stay clear of the border area.
32. Using a small cotton ball make small circular motions through the graphite with no more than moderate pressure.
33. Continue rubbing and spreading the graphite into all areas of the diaphragm, stopping very abruptly at the inside of the border.
You can tell when you have been on an area long enough because the cotton will move around smoothly with less resistance.
34. Carefully put a small amount of graphite in the area designated for the bias connection and rub it in with a cotton swab, use enough to insure a trouble free contact area.
35. Carefully but thoroughly vacuum off all traces of excess graphite with a brush attachment, try to keep smearing of graphite to a minimum in the border area.
36. Place waxed paper under a drilled stator on a hard work surface, wire side up.
37. Pull 37 1/2" of foam tape from the roll and place it on the long side nearest you. The inside edge should be close to, but not touching the first row of wires, be careful to keep it straight the adhesive is very tenacious. Repeat this procedure on the opposite long side.
38. Cut 4 1/2" of foam tape making sure to cut squarely. Place this piece on one of the extreme ends (1/2") to cover that row of grid squares and the wire loops. Then carefully trim the excess foam to fit perfectly with the end of the long piece it will be butting up against. Then do the same with the remaining 4" end. Turn the stator over and trim the 1/2" excess foam from the ends with a sharp utility knife. (Spacers will be 1" wide on the sides and 1/2" wide on the ends
You should now have foam spacers completely surrounding the periphery of the wires.
This tape is also used to mount the cells to a baffle in the final system construction.
39. Go back to the diaphragm with the stator you just applied foam tape to and orient it so the drilled ends are on the left. (Wire side down)
Make sure the drilled hole at Grid Square # 31 centers up with the area marked off for the bias connection.
Having confirmed this, return the stator to the previous workspace. (Wire side up)
40. Put on surgical gloves to avoid fingerprints and cut out a "T" shaped piece of aluminum foil.
The top of the "T" should be 3 grid squares long, the bottom can be about 2 ", the width of the cut should be just under 1/2".
Make 4 evenly spaced holes across the top of the "T" with a paper punch.
41. Make certain the drilled end of the stator is to the left, peel off the protective paper on the long side of the stator that will match up with the bias connection on the diaphragm. 42.Centered at grid square # 31, place the dull side of the "T" shaped foil on to the foam so that the bottom of the "T" centers up with and runs down past the drilled hole for the bias connection.
Trim the foil to a length that will allow it to fold under the stator and inside the edge of Grid Square # 31 and pass the backside of the hole.
Remove the protective paper from the remaining sections of foam tape.
43. Carefully lift the stator by the edges and carry it to where the diaphragm is located.
Have an assistant help you line up the stator over the lines drawn on the paper and make sure the end of the stator with the drilled holes is to the left matching the layout on the paper.
When you are sure everything is centered up, lower the stator on to the diaphragm.
Press firmly all around the outside edges of the stator.
Then use a short piece of the protective backing paper and a pencil to gently push the center of the entire outside of the perimeter grid squares.
The diaphragm should be well mounted to the foam tape, this is why the foil contact was punched with holes, to continue providing a bond across that area.
(Before turning the cell over, ground the bias connection to a cold water pipe)
44. Turn the cell over and put a length of waxed paper under the stator. (Disconnect the ground wire) Then cut pieces of foam tape to fit exactly over the first layer of tape, be careful not to puncture the diaphragm. Carefully but firmly press down on the tape all the way around the cell.
Turn the cell over and trim the excess 1/2" foam tape from the ends with a sharp utility knife.
45. Turn the cell over again and remove all of the protective paper backing from the foam tape and locate an additional stator.
Position the additional stator wire side down and the drilled end to the left to match the stator below it, have an assistant help you lower it on to the foam tape.
Press firmly all around the periphery.
You should now have a nearly completed cell, except for connecting stator wires to nuts and bolts through the drilled holes.
46.Locate a 4-40 x 1/2" machine screw and slide a # 4 flat washer onto it, place the screw through the outer most hole of the drilled cell square on the left end of the stator.
Have the threaded side of the screw exit the hole to the outside edge of the stator and place another # 4 flat washer over the screw and finger tighten a 4-40 nut onto it.
47. Turn the cell over and repeat the procedure in step #50 for the remaining hole at the end of the cell.
Strip 1/2" from the wire nearest the screw you have just installed and pass it through the nearest hole. Loop the end of the wire and place it between the screw head and washer, tighten down with appropriate hand tools (be careful not to crack the plastic).
Turn the cell over again and repeat this procedure with the nearest wire, clip the two remaining wires and discard.
48. Punch a hole through the hole for the foil at grid square # 31, place a 4-40 machine screw through a # 4 washer and mount it through the hole in the same manner as the stator connections.
Put an additional washer and nut on all screw shafts for external wiring.
Use all of the above steps to complete 4 cells.
CELL CONSTRUCTION IS NOW COMPLETE
In the event that a diaphragm was stretched too tight or was damaged in some manner, it will be necessary to dismantle the cell.
You will need a utility knife featuring snap off blades.
These knives have an extended cutting length available to them and need to be adjusted so the length of the blade is long enough to reach all of the foam tape without nicking the stator wire.
Start by disconnecting and removing the two stator connection bolts and the bolt for the bias connection.
Set the utility knife for the correct depth and carefully start cutting through the center of the spacers where they join the diaphragm.
The outer perimeter of the stators will serve as a guide to keep the blade from cutting too deep.
It will take several passes around before the stators will separate, be careful and patient.
Once you have successfully separated the stators, pull off all of the loose foam and diaphragm film from both stators.
Pick the rest of the foam tape off with your fingers, the rest of the adhesive is rubbed off with a rolling action using a spare piece of foam tape.
It's very important to keep the top surface of the grid squares smooth, don't scrape or scratch them.
To finish the cleaning job use a little isopropyl alcohol on a clean rag to remove all traces of adhesive, make sure the surface is dried thoroughly.
Start at step #29 to restore diaphragm and complete cell reconstruction.
The adhesive used for the foam tape is acrylic based, a brief firm pressure during application is desirable for a good bond.
This adhesive also works best at room temperatures of 70 degrees and above.
Initial bonding improves after 20 minutes and will continue to improve substantially with natural aging. Allow cells to rest for a few minutes after joining stators together.
IT IS VERY IMPORTANT THAT YOU DO NOT HEAT SHRINK THE DIAPHRAGMS UNTIL YOU KNOW IT'S NECESSARY TO DO SO.
Heat shrinking the diaphragms should be avoided unless you have the following test equipment available to you.
AUDIO SIGNAL GENERATOR -DIGITAL MULTIMETER -ANALOG SPL METER
The XEN bias supply is high impedance, low current device does not attempt to measure high voltage directly, and readings will be completely erroneous.
For the highest quality of performance possible, we strongly recommend using two XEN bias kits and the test equipment listed above.
Heat shrinking a diaphragm without knowing it's fundamental resonance will raise the resonance beyond design parameters; this will severely impede overall bass quality.
The following tuning procedure requires the cell under test to be connected to an acceptable matching transformer, a XEN bias supply and equalized amplifier.
1. Prop the cell up vertically away from walls or large objects parallel to it and connect it to the matching transformer
2. Connect an audio signal generator to an amplifier through the ESL equalizer and set the output frequency to 40 HZ.
3. Switch on all equipment and set the amplifier gain control to a low to moderate level.
4. Connect a digital multimeter to read D.C. volts (test point on diagram in XEN bias kit)
5.Adjust a spl meter to one of the lower scales, "C" weighting and fast response.
6. Hold the meter about 12 inches from the center of the cell and slowly adjust the bias output control between 10.0 and 40.0 D.C. volts. (Higher voltages may be needed at higher humidity) What you are looking for is a peak output that will very gradually fall if the voltage is raised or lowered on either side of the peak. (We call it tuning)
If you don't find a peak at that range, it will be necessary to widen the adjustment range.
If you find the peak above 75 or 80 volts, the diaphragm is already too tight and the cell will have to be dismantled for diaphragm replacement. (See cell construction #34)
Heat shrinking with a heat gun may damage diaphragms and stators.
7. When the diaphragm tunes below 5.0 volts it will be necessary to heat shrink it.
Shut off the power to the equipment. (Leave the signal generator on for stability)
Hold a hair dryer about an inch or two away from the cell and quickly go over the cell from end to end for about 5 seconds.
Let it cool down a couple of minutes and check the tuning again, repeat as necessary.
The ideal goal is between 15.0 and 25.0 volts (about 5000 actual diaphragm volts), once this is accomplished match the other three cells to this one as close as possible. Once done the cells should remain stable for a long time. (Higher humidity requires higher settings)
XEN PRICE LIST
Urethane Foam Tape
1" wide by 108' long enough to build and mount four ESL cells for a stereo system, this is high quality American-made foam tape.
You will still have tape to spare for replacing a diaphragm, should it become necessary.
Along with the tape you will receive a 25' roll of polyvinylidene choride film, plus construction plans on our unique folding baffle design that enhances bass while still providing true dipole operation. $64.95
Over 1600 feet of our special stator wire will allow you to build four of our insulated cells for a stereo system, plus have enough left over to build a spare cell.
This small diameter wire features a special insulation that lets you enjoy all of the music and none of the arcing. $149.95
XEN BIAS SUPPLY KIT
Our bias supply kit was designed especially to work with our insulated ESL system.
It features very high impedance and extremely low current; it adds no noise to the ESL system to preserve all of the dynamic range.
We supply all active and passive components including power supply plus circuit diagram with description, you supply a plastic case, pertinent hardware and perfboard.
Because of XEN's unique tuning system, we strongly urge you to use two separate bias kits for optimal bass performance. $59.95 ea. or two for $99.95
XEN ESL EQUALIZER KIT
This is a dedicated stereo equalizer designed to be used expressly with the XEN ESL system.
Our equalizer kit consists of a gain stage, a passive asymmetrical bandpass network and buffer stage.
It can be introduced into a tape monitor input, or between a preamp and power amplifier.
We supply a circuit diagram with description, all active and passive components including power supply and gold plated input and output connectors for two channels.
You supply pertinent hardware and perfboard. $59.95
We've found a well made 150: 1 matching transformer that provides the best performance for our ESL's.
We have put this transformer through its paces for a few years now, with truly impressive results.
This unit is no lightweight; it has considerable size and weight to it.
We don't stock this item but we've talked to the company that makes it, and they would be delighted to hear from our customers directly.
Here is where they can be reached.
2350 Executive Circle
Colorado Springs Colorado, 80906
STOCK # 2-0404, their price is $140.00 ea. Plus $10.00 shipping.
Hand Assembled Cells
Four hand assembled cells, tested and tuned and ready to be installed.
For those of you who prefer not to build your own cells, we offer you an alternative.
We realize that some people may be more interested in the tweaking end of a project than the actual construction.
XEN's solution for you folks that rather tweak than build is to offer you hand assembled cells, fully tested, tuned and ready to be installed.
We hand assemble these cells, test and tune them with the very same equipment offered in our manual.
WE supply you with all data to adjust your XEN bias supply to the proper tuning voltage and which pair of cells matches for each stereo channel. (Some tweaking of the bias control might be needed due to variations in tolerance)
Included with the hand-assembled cells are one roll of foam tape (for mounting) and a copy of construction plans for our unique folding baffle design. $499.95
XEN will pay shipping on any combination of XEN products listed in this manual that totals over $300.00. (Within the contiguous United States of America)
Recommendations For Operation
It is advisable to fuse the input side of the matching transformer.
A fuse can be a somewhat arbitrary device, but our tests indicate using a fast blow rated between 4 and 5 amps should prove satisfactory for most situations.
Amplifier Power Requirements
An optimal amplifier power output of 100 to 200 watts is recommended for best results with XEN ESL's. (We recommend running all tone controls in their flat position along with mandatory equalization)
Amplifier outputs between 25 and 50 watts are usable at the expense of higher spl's.
The Tranex 2-0404 matching transformer has a maximum input voltage rating of 100 volts a. c. peak to peak plus or minus 10%, please take this under consideration.
XEN ESL's work best playing into the long part of a room.
XEN ESL's need room to breathe, place them about three feet from a rear wall and about two feet from sidewalls.
Angle the ESL's in slightly once an optimal listening position is secured.
Holding a flashlight under your chin check to see the light reflecting from the diaphragm of each channel, adjust the position of each ESL accordingly.
Generally the best low bass is found close to the opposing wall facing the front of the ESL's.
If possible, connect an audio signal generator set for 40 Hz. to the driving amplifier set for monaural, then walk back into the listening area with an spl meter to observe the strongest peak.
It would be a great disadvantage to have a listening position placed directly on a low frequency null.
No two listening rooms are alike; you must find the best placement and listening position empirically.
XEN ESL's have a very satisfying and balanced low frequency output when the ESL's and listening position have been optimized.
A Final Word
An aural evaluation of a loudspeaker system is a subjective opinion; performance claims by XEN are based on what we believe to be forthright opinions of our products and construction techniques.
It is assumed that you have a working knowledge of electronics and construction techniques in general, a neophyte may find this project a somewhat dynamic undertaking.
XEN does not knowingly conduct business with minors.
All sales are final.