ESL57 bass panel from scratch

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After re-building ESL 57 panels, next step: build a bass panel from scratch.

For this I need some information:what is the exact drill size for the 3*1183 holes in the stator (active zone) ?
I measured something slightly above 3mm. The problem is that it might be an imperial size.

Drill size Diameter (in) Diameter (mm)
...
3 mm 0.1181 3.0000
#31 0.1200 3.0480
3.1 mm 0.1221 3.1000
1/8 in 0.1250 3.1750
3.2 mm 0.1260 3.2000
...
(source: Drill Size Chart - Machining)

Even some guess might help: maybe Quad had some habits wrt which unit to use when designing its products.
 

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Hi,

Sorry that I don't know anything about the hole size you ask, but I am very interested in your project. What material do you plan to use for the bass panel? Can you share with us the dimensions?

Wachara C.

My intention - provided I go up to completion of this project (*) - is to build something close to original.
Thus dimensions are simply those of an original panel. Just open one and you will get all needed information. For example they are made of 2mm plastic, same for spacers, ...

(*) I am not convinced that there is need for such project: bass panels can always be re-built. Thus just for fun ?
 
Fabien,

Does it really matter? I mean I ordered a pair of replacement middle/tweeter panels from Quad itself (some 20+ years ago) and the replacements were sligthly different both physically and in measured frequency response. There is a chance that a little deviation makes the result better (or worse) than the original.
 
Fabien,

Does it really matter? I mean I ordered a pair of replacement middle/tweeter panels from Quad itself (some 20+ years ago) and the replacements were sligthly different both physically and in measured frequency response. There is a chance that a little deviation makes the result better (or worse) than the original.

Well I think that the hole size in the active zone is the only dimension that really matters. Yet this is indeed a minor issue.
Has someone some kind of PVC to suggest to make these stators ?
 
large-scale commercial production of isotactic polypropylene from 1957 onwards.

I have only disassembled a Quad ESL 57 tweeter, and its in a different country from me right now. From memory the panels looked like a thermo plastic, and its manufacture looked very simple and possible in a workshop.

To clone Quad ESL 57 tweeter (I would buy one if not doing it as an exercise in manufacture or basis of my designs) I might take a molding of the inside and use that as the former for simple heating with a molding jig (though I would be tempted to design my own, similar solution), if Quad also used heat molding of sheets approach, with 1/8inch plastic sheet, the thickness in some areas of the plastic would be less. I should not expect the thickness of the plastic is that critical, but the hole depth might be.

For simplicity and with a pillar drill I would drill before molding, with the right temperature the holes should remain through molding, as the plastic becomes like heated cheese, in this consistency the jig should be apply force to the stators around the molding similar to vacuum packing.

The aluminium foil coating could also go on before as the heating may help bond the foil layer, and make manipulation easier, and probably wont hurt it, and cleaning the hole edges might also be simpler while it is a flat sheet of thermo plastic.

Then I would put the plastic in an old oven strapped into a simple jig to corrugate the sheet in the way I assume Quad did. It would be an interesting project.

I think the real genius in Quad is their manufacturing products of high consistency with out the need for highly skilled manufacturers. Is Polypropylene a good candidate electrically or just good for the heat forming manufacture?

I cant help noticing this from wikipedia;
History

Propylene was first polymerized to a crystalline isotactic polymer by Giulio Natta and his coworkers in March 1954.[3] This pioneering discovery led to large-scale commercial production of isotactic polypropylene from 1957 onwards.[4] Syndiotactic polypropylene was also first synthesized by Giulio Natta and his coworkers.
Is this just a coincidence ?
 
Quad esl57 stator uPVC

This info was posted quite a while back over on audioasylum but since it has probably been archived and forgotten.

The original stator material that Quad used in the ESL 57 was a rigid unplasticised PVC sheet, also known as uPVC, brand name “Darvic” this information came straight from Mr. Robert Flain of Quad.

Polypropylene is too soft a plastic to use to maintain its shape after perforation. The holes were hot press punched by the way and for the hobbyist the best alternative would be to set up a jig and drill a stack of PVC sheets but that many holes will be tedious. Unless you happen to have access to a machine shop or plastics company that would press punch the PVC for you but then the minimum order and setup fees would exceed the price of a used set of Quad esls.

The consistency of thickness of the stator will affect the performance of the panel and is a critical parameter of the manufacture of the esl if one is attempting to replicate the original Quad esl panel as closely as possible. A few years back there were some audio engineering papers published which discussed mechanical inconsistencies (thickness, distance gap, warping etc.) in stators as being a major cause of distortion in electrostatic speaker systems; but I cannot recall at the moment the exact reference, someone else can probably cite the source.

Hope this is of some help.

One source of pre-perforated PVC sheet is San Diego Plastics at, Perforated PVC sheet

As for any other considerations; the jig and weight setup you use to tension the mylar should be given considerable time and attention to insure consistency, and be sure to use the “Calaton CB” soluble Nylon suspension for coating the mylar or at least the DuPont Elvamide nylon resin.
 
This info was posted quite a while back over on audioasylum but since it has probably been archived and forgotten.
...
Thanks for the detailed info.
This confirms the use of uPVC, which I managed to find in my country I think (thickness:2mm).
With regards holes, my intention is to drill them using a CNC machine which is under construction by s.o. I know.
I already have a jig. The 28 weights are ready - although I would be thankful to anyone confirming the right value to use - and I use Elvamide as coating.
I already have good results wrt repeatability for bass panel, less for treble panel. But this is improving.
All that to say: this project might come to reality soon.
 
Hi,

apart from some romantic feelings, is there any hard fact why to rebuild such an old design? One of the key advanrages of ESLs is that they allow for single driver fullrange systems or Subwoofer assisted widerange systems. One doesn´t need to build an ESL after the same fashion one would build a 2-way dynamic speaker with the crossover frequency in the lower kHz range. In short: Why plague oneself with the task of designing a crossover when one can omit with it, easen the design and still get better results?
I wouldn´t also go for the task to build stators from a soft PVC material.
You can easen and speed up the design by using standard FR4 PCB material. Its easily and cheaply available and the conductive pattern and hole pattern can be produced after Your fashion. The conductive pattern can furthermore be optimized wrt to insulation against flashover. The dielectrical properties of FR4 are at least as good as PVC and the material is stronger, allowing for a lower thickness (which increases bandwidth, that may otherwise be limited with a 2mm thick stator).

jauu
Calvin
 
I agree with Calvin that FR4 PCB should be a better alternative to the soft PVC material.

Wachara C.

If the intent is to rebuild the Quad to similar specs then FR4 is not a good choice. It will sound completely different from PVC, the latter having much better internal damping. Quad ESL replacement panels using FR4 have been and are being produced and are generally considered inferior to the original sound wise. These FR4 stators ring like a bell.
 
Hi,
apart from some romantic feelings, is there any hard fact why to rebuild such an old design?

I understand your remark this way (tell me if I'm wrong): is it worth-it re-building an ESL57 ?
Well my personal feeling is that it is indeed the case.
I agree that making an ESL 57 bass panel from scratch might be useless since bass panels can almost always be repaired. Yet this is a reasonable step for me.

If I was to build my own ESL, I would consider something else than PVC. Maybe PCB as suggested, maybe fiber-glass (for increased thickness).

Meanwhile, I am focusing on re-building my ESL 57 as close as possible as the original. Including defects.
 
uPVC vs. FR4 for stators

Pardon me, but both Calvin and chinsettawong must have confused materials specifications, rigid “Unplasticized”, uPVC, has greater rigidity than the common flexible PVC does. According to some references I checked, rigid uPVC has a flexural strength of at least 700 MPa or greater which can be close to the specs of some of the thinner and lower quality FR4 material out there. They may have been looking at the specifications for common plasticized PVC which only has a rating of 70 MPa or less.

A few quick references,
Handbook of thermoplastics by Olagoke Olabisi
Handbook of Materials Selection Edited by: Kutz, Myer,
and Datasheets from plastic suppliers,
Plastics International and Boedeker

Furthermore, in the United States the cost of large sheets of FR4 material exceeds the cost of uPVC which is not exactly cheap itself at around $400 for a 48” by 96” sheet.

Also, the OP was attempting to replicate or “Clone” the original Quad ESL 57 speaker as closely as possible which is an entirely different objective than building a new ESL design.
 
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