I have been rebuilding a pair of Quad ESL-63s and am getting close to finishing. By rebuild, I mean I have reglued stators, and replaced diaphragms in all eight drivers.
I used Gorilla clear polyurethane glue to glue the stators of only one speaker- the other stators were bonded well and would probably have broken if I tried to break them loose.
I used 3 um mylar film, stretched using a pneumatic stretcher, with resonance tuned while the film was on the stretcher to about 92Hz. The diaphragms are glued using 4693H contact cement that unlike the factory glue, actually bonds to the grid and the diaphragm.
I applied Licron Crystal to the diaphragms and tested resistivity and resonance before and after applying the Licron. Resistivities all came out at either 10^8 or 10^9 Ohms/square. Resonance dropped by about 1 Hz with the added mass of the Licron Crystal. For those who might be concerned about longevity, I have some old drivers that I worked on in the early 90s that used 4693H and Licron coating, and they are still in good shape.
You can see details of my failed and successful methods on my blog page, here.
I'll be installing the drivers back into the speakers and testing with full bias applied over the next couple days.
I used Gorilla clear polyurethane glue to glue the stators of only one speaker- the other stators were bonded well and would probably have broken if I tried to break them loose.
I used 3 um mylar film, stretched using a pneumatic stretcher, with resonance tuned while the film was on the stretcher to about 92Hz. The diaphragms are glued using 4693H contact cement that unlike the factory glue, actually bonds to the grid and the diaphragm.
I applied Licron Crystal to the diaphragms and tested resistivity and resonance before and after applying the Licron. Resistivities all came out at either 10^8 or 10^9 Ohms/square. Resonance dropped by about 1 Hz with the added mass of the Licron Crystal. For those who might be concerned about longevity, I have some old drivers that I worked on in the early 90s that used 4693H and Licron coating, and they are still in good shape.
You can see details of my failed and successful methods on my blog page, here.
I'll be installing the drivers back into the speakers and testing with full bias applied over the next couple days.
Looking for your future posts, mine failed after 30 years and I am considering re-building them soon.
Thank you very much for sharing your experience and data.
Thank you very much for sharing your experience and data.
Drivers are in on the first speaker. tested first with just bias applied- dead silent! Then I hooked up an amp and gave it some music- PERFECT!
I just finished replacing the first dust cover- I'm not too happy with it- there are wrinkles I was unable to chase out with a heat gun. I cranked up the music and didn't hear it rattling, so maybe it's OK. I'm not sure if the original dust covers were wrinkle free. I'm going to have to think about the technique to use for this.
I just finished replacing the first dust cover- I'm not too happy with it- there are wrinkles I was unable to chase out with a heat gun. I cranked up the music and didn't hear it rattling, so maybe it's OK. I'm not sure if the original dust covers were wrinkle free. I'm going to have to think about the technique to use for this.
You might also contact Quad Musikwiedergabe in Germany in case of questions:
https://www.quad-musik.de/index.php/en/refurbishing
They bought the original ESL production equipment from QUAD UK and might assist in refurbishing.
https://www.quad-musik.de/index.php/en/refurbishing
They bought the original ESL production equipment from QUAD UK and might assist in refurbishing.
A heat gun is a dangerous tool for removing wrinkles. I prefer an ordinary hair dryer, even that from a safe distance and continuos moving.
My method was (with an ESL-57) to lay down the mylar flat on a glass table, apply some glue around the frame, place the frame onto the mylar, press the circumference with some weight until the glue cures, cut excess mylar, position the dust cover in place and fix it, then sweep with the hair dryer. No need to overtighten it.
My method was (with an ESL-57) to lay down the mylar flat on a glass table, apply some glue around the frame, place the frame onto the mylar, press the circumference with some weight until the glue cures, cut excess mylar, position the dust cover in place and fix it, then sweep with the hair dryer. No need to overtighten it.
They have one of the very old, very first 57 jigs, that is totally different from the one Quad used for the ESL-63. Apples and oranges.
This is what the original 63 tensioning jig looked like.
10x more tensioning points in this 63 jig compared to the 57 model.
This model was never sold. Maybe even still in use in China.
The 57 model is just some weights hanging down from pulleys attached with clamps.
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I've seen photos of the factory jig before. Crazy!
Here's my diaphragm tensioning jig. It's an improved version of one I invented back in the 80s when I started making ESL. It has a bicycle tire tube around the perimeter of the jig. There's double stick tape on the underside. You just wrap the film over it, stick it to the tape and put some air in the tube. All the wrinkles disappear and you can get the film as tight as you want it.
I can measure and tune the resonance by adjusting the air pressure in the tube, while the diaphragm is on the jig. I excite the resonance by thumping the diaphragm with a steel ball hanging from a thread. The RTA in REW plots the spectrum of the signal from the UMIK-1 mic.
After I tune the resonance I glue the grid to the film and then test resonance again using the same technique. There's a slight difference is size between my jig and the ESL-63 grid and the result is that the diaphragm resonance on the grid is always about 10Hz higher than on the jig, so I just set the resonance on the jig about 10 Hz below the target and it comes out fine.
Here's my diaphragm tensioning jig. It's an improved version of one I invented back in the 80s when I started making ESL. It has a bicycle tire tube around the perimeter of the jig. There's double stick tape on the underside. You just wrap the film over it, stick it to the tape and put some air in the tube. All the wrinkles disappear and you can get the film as tight as you want it.
I can measure and tune the resonance by adjusting the air pressure in the tube, while the diaphragm is on the jig. I excite the resonance by thumping the diaphragm with a steel ball hanging from a thread. The RTA in REW plots the spectrum of the signal from the UMIK-1 mic.
After I tune the resonance I glue the grid to the film and then test resonance again using the same technique. There's a slight difference is size between my jig and the ESL-63 grid and the result is that the diaphragm resonance on the grid is always about 10Hz higher than on the jig, so I just set the resonance on the jig about 10 Hz below the target and it comes out fine.
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I have completely finished one speaker and the second one 95% finished. I discovered that its fuse holder was broken last night when I was going to test the speaker. I have ordered new fuse holders and will replace them in both speakers, and finish off the second speaker tomorrow.
I have some serious criticism of the design/manufacture of these speakers.
1) The dust covers are ridiculous. The frame isn't solid until you snap it into the speaker, but you can't put the film on while the frame is on the speaker because it sits inside the rest of the driver frame. There's no way to put the film on the frame when it's off the speaker and know that it won't be wrinkled when you move it to the speaker. The drivers mount on two aluminum L brackets, and that assembly can be dropped into the driver housing. That assembly should have included frames for the dust covers, or maybe dust covers should have been a part of each driver.
2) Too much use of foam tape. I spent at least 3 full days cleaning the rotted foam and the adhesive residue out of these speakers. Some of it seems entirely unnecessary, such as the strips on the aluminum L brackets where the drivers mount. They don't cover the whole surface of the driver's edges, so what's the point of it?
3) Adhesive that doesn't bond to the diaphragms. The stuff has zero peel strength, so they are relying on shear strength of the very weak "bond". It's no wonder they fail.
4) Overly complicated and flimsy driver enclosure frame - plastic top and bottom pieces and thin aluminum extrusions on the sides, with 4 aluminum sticks near the center. What were they thinking?
5) The electronics housing is a thin plastic box!
6) Steel protective grids fit into slots in the aluminum side pieces, but are taped to the frame at the top and bottom. Why wouldn't they have screwed them to those top and bottom pieces? I think they were trying to bolster the flimsy construction of the driver enclosure by taping the grids to them.
I don't know how they managed to ship these things and have them work properly when they arrived at their destination. It seems like Quad didn't have any manufacturing engineers on staff or these things would have never made it to production.
I have some serious criticism of the design/manufacture of these speakers.
1) The dust covers are ridiculous. The frame isn't solid until you snap it into the speaker, but you can't put the film on while the frame is on the speaker because it sits inside the rest of the driver frame. There's no way to put the film on the frame when it's off the speaker and know that it won't be wrinkled when you move it to the speaker. The drivers mount on two aluminum L brackets, and that assembly can be dropped into the driver housing. That assembly should have included frames for the dust covers, or maybe dust covers should have been a part of each driver.
2) Too much use of foam tape. I spent at least 3 full days cleaning the rotted foam and the adhesive residue out of these speakers. Some of it seems entirely unnecessary, such as the strips on the aluminum L brackets where the drivers mount. They don't cover the whole surface of the driver's edges, so what's the point of it?
3) Adhesive that doesn't bond to the diaphragms. The stuff has zero peel strength, so they are relying on shear strength of the very weak "bond". It's no wonder they fail.
4) Overly complicated and flimsy driver enclosure frame - plastic top and bottom pieces and thin aluminum extrusions on the sides, with 4 aluminum sticks near the center. What were they thinking?
5) The electronics housing is a thin plastic box!
6) Steel protective grids fit into slots in the aluminum side pieces, but are taped to the frame at the top and bottom. Why wouldn't they have screwed them to those top and bottom pieces? I think they were trying to bolster the flimsy construction of the driver enclosure by taping the grids to them.
I don't know how they managed to ship these things and have them work properly when they arrived at their destination. It seems like Quad didn't have any manufacturing engineers on staff or these things would have never made it to production.
The goal was not to make the most sturdy glamorous speaker, the goal was to make the best possible electrostatic speaker for little money and not make it a boutique product. They managed that quite well. When everything is connected together stiffness comes in little steps. Using other materials would have been a huge price increase.
Please note that only 10-25% of retail price can be spend on production and parts in a manufacturer-imported-distributor-retailer model.
The rest goes to Marketing, shipping, distributor, retailer, taxes etc.
With modern technologies you can make improvements, but also only that much within the constrains of the system without making it too bulky.
The later 05 and 12 models look better, but audio construction wise it is not.
Look at other brands of the period, they look like half finished DIY projects. This design has custom made injection moldings, extrusion aluminium, extrusion plastic etc. instead of a painted plank with wires.
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My ESL63 came with the Arcici stands which were highly recommended at that time (late 80s) for structural rigidity.
Mark: if you have amplifiers of the right maximum output voltage, I recommend trying to disable the protection/clamping circuitry, there is a big improvement in the dynamics.
😉
Mark: if you have amplifiers of the right maximum output voltage, I recommend trying to disable the protection/clamping circuitry, there is a big improvement in the dynamics.
😉
Given the complexity of the construction and the necessary development of an more or less economic production process it is no wonder it took Quad 18 years to bring the ESL 63 to market (1963-1981).
Not crazy at all if you have to make production quantities. Your "jig" is fine for a few panels, not for hundreds, even thousands.
Quad jig. Slap the Mylar in from the role, close the clamps by a push of a button, tension by a push of a button, swing down frame to mark borders to apply electrostatic coating, apply coating with a brush, swing stator frame with glue applied down. Done, next.
Oh wait, there was an oven involved somewhere in that process.
I'd have to disagree there. I think a folded steel frame (or even MDF) would have been cheap, more rigid, and cost a lot less to assemble, and there would probably have been many fewer under-warranty repairs. At $4k per pair in 1983 these were boutique speakers.
Back in the 80s there were two "popular" methods to tension diaphragms. One was to try to pull tension by taping the diaphragm to a table, the other by taping it to rollers parallel to the X and Y axes of the driver. Neither of those methods allowed very much tension to be applied (the rollers were just plain wrong) or to know the resonance of the driver in advance of gluing it to the frame. I think my pneumatic tensioner is much better than any of those methods.
The tensioner they use at the linked site looks like it's just a small step above what hobbyists were doing in the 80s.
Thanks for the link, but my speakers are all but finished- until I decide to rebuild them with extra bass panels, similar to the 989s, but much more rigidly constructed (maybe welded steel frame).
it is amazing you got such high res by the way on the 3 micron ! i had a hard time to reach 75hz (it has been a while so numbers might be off a litlle, i think the originals where in this region according to my measurements, then again they where old panels as well so who knows) keep in mind they used heat while stretching on the ESL63. my thoughts on that is they cant get the desired res by over streching, since it will rip. by heating the foil the drop after a few days is far less then without heating. so they did not have to over strech as hard . there is a topic somewhere here. where i used heat and without heat and plotted the drop in res. maybe the 95 will drop to the 75 hz.. i hardly managed to strech it that hard. quite a few ripped foils 🙂 i did use the same bicycle jig 🙂
And with steel it would ring like a bell. Tried that, done that, been there.
I will make a video with sound from the ringing and weight of different materials I used for the top and bottom plate.
In a completely different construction or MDF I don't know what the result would be. Looking back things always look easy
The composite material is acoustically dead, aluminium and steel are most definitely not.
The warranty claims were (and still are) about stator glue failing, not construction problems. Maybe only on transport of the 989 series where dust covers were already damaged on arrival due to smaller grille -> dust cover distance and flexibility of the longer frame.
Retail price was £ 575 incl. VAT in 1982 in UK, that is $ 1.100 US at the exchange rate of the time. VAT was introduced in 1973 in the UK and was 15% in 1982. So excl. VAT £ 490 and $ US 935
The rest was transport, importer margin, retailer margin, marketing, insurance, taxes etc. Money that Quad could not spend on manufacturing.
And now again think of the percentage of the retail price that can be spend on production (see my earlier post)
They had a weight constrain. I read an article that they managed to reduce the weight from the earlier prototypes with almost half! So they could ship them much much cheaper.
I guess Walker was not 100% happy...