Mendo from Italy has kindly provided us with a description of the repair process including some modifications he made to the process in Italian, we have copied it below in English. The Italian version is HERE.

I have two Quad ESL63 speakers since 1983. They had been stopped for about 10 years now and I had recently thought of renovating them, but I didn't have them idea of how to do it. So I started off well and started surfing the internet for see if I could find something that could help me. I came across the ER-AUDIO website of Australia. At first I was not entirely convinced but then I decided to buy the repair kit. All this in mid-December 2018. The kit arrived on 10 January 2019. I started the renovation of the two ESL63 Quad speakers in mid-January 2019. First job the complete disassembly of the diffusers the removal of the stators. The parts are there disconnect quite easily. First hitch, a pair of stators had a burn that had also perforated the diaphragm, so I decided to do an accurate repair. In the pictures below the interventions carried out are highlighted:

Mendo 1

Front stator and rear stator

Mendo 2

Repair completed

Mendo 3

Once the two stators were repaired, I started cleaning them up. After a grueling work that involved great patience and precision is the result:

Mendo 4

During the removal of the stators from the grids I found a panel repaired, to say the least strangely, done directly in the factory by the Quad (the speakers were purchased by the official importer and the packaging was intact and sealed at the factory). In the picture below interventions with the addition of glue from the outside of the stators are visible.

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After cleaning, I proceeded to glue the stators to the plastic grids and tighten them between two 19 mm MDF panels. purpose built.

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Now before starting to glue the diaphragms I preferred to build a panel to carry out tests to see the result.

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I note that the first attempt at sticking in the test panel did not go well because I removed the weights after about 24 hours but the glue had not caught on completely, so I re-glued the diaphragm waiting for safe drying (5 days).

The work surface for diaphragm tensioning. The tape provided in the kit was not sufficient so I bought another one. The one supplied in the Kit was black while the one purchased is gray.


Note from Rob, We explained to Mendo that if we included a larger roll of tape the additional weight would send the package into the next charge scale for postage. This made around a $20.00 increase, an additional roll of tape is not that expensive.

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The photo below shows the method used to bond the diaphragm to the panel:

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As said before, after 5 days weights are removed, the result is satisfying:

N.B. The photo below shows the four panels of a speaker that had stability problems.

- No. 1 Panel at the top had no problem with leaks or discharges
- No. 2 is the panel in which the repair was made (visible in the center of the same)
- N. 3 Panel replaced about 20 years ago and as you can see is of the second generation
- N. 4 Panel at the bottom also this no problem of discharges

Mendo 10

Notice on the right side the temperature and humidity meter

In the photos below the repaired panel is visible. In the inserted insert and for about 8 mm, a layer of high voltage insulating paint was applied around it.

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Mendo 12

In the picture below are some panels ready for the application of conductive liquid

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For the application of the conductive coating I built a mask to avoid smearing in wrong parts and I must say that it worked perfectly.

Mendo 14

As you can see, the mask covers a fraction of the grid to prevent the conductive coating to overflow towards the outside of the panel

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In the picture below the conductive coating has already been applied. If you look carefully you can see the circle not applied around the central turrets as marked in red.

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After the conductive liquid has dried, I smeared a thread of the same liquid (concentrated) at the contact with the aluminum strips to carry the high voltage for a width of 3-4 millimeters taking care not to overflow to the outside.

I also built the liquid container using a part of a syringe and a piece of plastic
(see photo). Not even a drop of liquid was wasted with this system.

Mendo 17

In the manual it is specified to use the syringe to take a quantity of liquid 2 ml,
but I found a much more practical system. I took 2 ml. of distilled water from one
bottle with syringe so I measured how many drops match (I did several
tests to be sure of the quantity) and I have established that for each panel 64 drops are needed of liquid and 32 drops of distilled water. This allowed me to apply the exact amount of liquid in the diaphragm.

The photo below shows the tools used for applying the conductive liquid.
N.B. The instructions say to use exactly half of the liquid supplied (as per the manual the liquid is sufficient for 16 panels visible in the photo). Same situation for consumption glues for stators and diaphragms. All 16 stators and 8 diaphragms have been re-glued.


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When I finished applying the conductive liquid after waiting for 24 hours I drew one strip of the same liquid (but concentrated) along the upper and lower edges so as to get better contact with aluminum strips, being careful not to spill over on the sides of the panel.

After finishing all the gluing and application of the conductive liquid
I wanted to check the resistance values of the diaphragms. So to take measurements I built a high resistance meter (see photo)


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Note from Rob. It’s not absolutely necessary to measure the surface resistivity of the coating, the rate of dilution has been determined to give the correct reading.

This instrument coupled with a digital multimeter can read resistance values between 1 megaohm and 1400 megaohm with an error factor of less than 1.5% .-
In all the measurements made in different points of the diaphragms I found values included between 500 megaohm and 1200 megaohm, values that were among those recommended in the repair manual.

After these operations I started to reassemble the panels.
Note: in the 7 black panels there were no spring clips in the panel white were planned. I purchased a certain amount of clips in order to mount 4 + 4 also in black panels.

Note from Rob. We supply 12 spare clips in the repair kit this is usually enough to replace any missing clips. In Mendo’s case all the clips were missing on the earlier panels so required more to be purchased.

Mendo 20

Once I reassembled all the panels and reassembled the speakers I started to give current to a panel at a time, checking for any parasitic noises. I didn't find any noise stranger. Reconnect all the panels to the high voltage I saw the famous neon light of control. With just one panel powered the activity signal appeared at about each minute while with all 4 panels live the value has dropped to about a pulse every 8 - 10 seconds in one speaker and about every 4-5 seconds in the other.

First listening test with the panels without any protection (no dust covers, cloth, mesh grille etc):


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The listening environment measures about 35 square meters with curtains on one side.
Equipment used : Sintopre Revox mod. B739, Revox Finale mod. B740, CD650 reader Philips, alternatively Raspberry with DAC AlloBoss pcm512

Present some friends of high fidelity.

The first impression was nothing short of devastating. (in a good way!! Rob).

All the people present had listened to the same ESL 63 about 15 years before and everyone has agreed that both the quality of the issue and the dynamics of that time had nothing in common with this session. What to say, we were all amazed by both the dynamics and the sound quality.

Second test session with the speakers completely reassembled


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The following is a note to us that accompanied this repair description with a couple of suggestions how we can improve the repair kit. The suggestions have been taken on board.

Dear Rob, I wanted to thank you for letting me savor the value of these speakers. I must tell you that at the beginning I was not very convinced of the success of the job because I didn't think of reposting these speakers at this level, I would have settled for resuming them like 15-20 years ago.
Now the painful notes (few for the truth)
The tape used for the diaphragm tension is not enough (it takes at least three rolls)
Even the double-sided adhesive tape for bonding the dust shields is not sufficient for the 4 panels (at least two rolls are needed)

I did not use abrasive paper but nitro solvent to clean the stators. the advantage
is that I have practically not scraped anything of the copper coating. the work was more long but the result was better, the stators are back as new.

For the application of the conductive liquid I used the dropper to determine the exact quantity to apply (64 liquid drops, 32 drops distilled water) much easier to use.
I did a test in the self-made frame to test the bonding of the diaphragm. After 24
hours I removed the weights and surprisingly the glue didn't take root so it came unstuck.
Solution, I left the panels glued for 5 days result the glue has dried well and
remained glued.

I added a string of concentrated conductive liquid to the top and bottom of the
stators about 3-4 millimeters wide where they are coupled with the aluminum strip which brings the high voltage charge to the diaphragm, being careful not to overflow (I am convinced of the best contact electric).

Our response to Mendo is below.

Hi Mendo,
Many thanks for going to the trouble of translating the manual into Italian and letting us have a copy, I’m sure it will help someone in the future. Your journey through the repair is also very interesting, with your permission I would like to publish it on our website.
I particularly liked the repair you did to the burned stator, this was very nicely done. In reality, a hole say 15mm x 15mm will not affect the sound quality too much, the hole is very small relative to the area of the panel, however, it is nice to see this done professionally.
Re your comments about the tape used for tensioning the diaphragm. We are aware that one roll may not be sufficient to rebuild a full set of panels especially if a couple of attempts to tension the film are made and are not successful. However a larger roll does not fit into the mailer tube easily and will take the weight of the kit into the next postage level, increasing the cost of shipping by around $20.00, much more than sourcing an additional roll of tape locally. I will make some notes in the repair manual regarding this.
We have accepted your comment about the double sided tape and will supply 2 rolls from now.
We are glad that the outcome of the repair was successful for you and that the final performance of the speakers was greater than you expected.
If we can be of any assistance in the future please don’t hesitate to contact us.
Best regards


Also with dust protection panels (the same material as the diaphragms was used) and the mesh grids, the sound remained almost unchanged.

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