Construction 1

First stage.
Feet and lower cross-bar assembled:

This assembly needs to be as solid and rigid as possible. It’s got to support weight, and it’s got to resist shearing if there is any force forwards or backwards exerted on the stack.

On each side I’ve put six 2″ screws through the side wall into the foot section, three more big 4″ ones into the end of the cross-bar:

and, invisible in the picture above, two more heavy 4″ screws downwards though the cross-bar into the foot.

Second stage.
First speaker into place:

I’ve put three small retaining screws per side through the frame into the wooden side-wall of the actual speaker. Note this is exactly half an inch thick. Be very careful in your drilling and the selection of screws. It would be a bit unfortunate to go through into the bass panel. They only need to go a few mm into the speaker side wall, the speaker is being held rigidly by the clamping force of the two side planks being pulled inwards to the cross-bars, which as mentioned are cut a couple of millimetres shorter than the width of the speakers.

The middle cross-bar is in place too. This will be supporting the upper speaker, so it has 3 heavy-duty 4″ screws fastening it to the side-walls at either end. It’s positioned so that the bottom of the upper Quad clears the top of the lower one by a couple of millimetres – so we don’t have the grilles scraping one another.

I’m pleased to see that it’s going to look quite neat and clean, much as I’d imagined it.

The laying out of parts

The first stack is ready for assembly apart from the top bar. That isn’t load-bearing and can wait:

By standing the speakers and cross-bars in place on one of the side walls, you can mark out their final positions as shown. Enlist a passing native to hold them steady. This will be helpful later, when you’re trying to hold things in place with one hand and drill holes with the other:

The plan

So the plan is very simple. Each stack to consist of:

1) Two side panels of 4 inch plank
 
2) Three cross-bars of 4×2, the bottom one with the lower speaker resting on it, the middle one with the upper speaker resting on it, the top one to complete the box. Actually the middle one can be less wide to reduce weight – if it’s 4″ it’ll stick out at the back. As discussed, I’m using wood reclaimed from skips, as the builders around here seem to chuck out nice clean planed timber. It’s good to have the top, bottom and sides all 4″ wide though, makes a neat and workmanlike box round the speakers. Of course you could go wider than 4″ (at some cost) and achieve greater mass and stiffness.
 
3) Two 2′ lengths of wood as feet, running fore and aft for stability.
 
4) Two castors per foot for moving the damn things about.

If the cross-bars are a couple of millimetres smaller than the width of the speakers, the screws running into them can be used to pull the side panels in tight against the Quads, clamping them firmly into place. A length of 835mm is about right for this.

The centre of gravity

The problem with stacking Quads is that they’re wide and awkward to handle and they weigh 18kg each – with the centre of gravity at the bottom where the electronics are.

Ideally one would remove the heavy audio transformers and the EHT supplies from both speakers, put them all in their own case at the bottom of the stack, and have wiring running neatly up the back to the panels. However I need to be able to unstack and restore the speakers relatively easily, so we’re keeping them intact. I have to keep the grilles on, because they’ll end up being used as the source for musical chairs and electrocution is not traditionally part of the game.

Also, let’s be frank, there’s a WAF issue with speakers 6 feet high and 3 feet wide. An important element of the design brief is to make them as small and, cough, inconspicuous as possible – but they’ll be on sufferance at first. If they prove too intimidating, they’ll end up being dismantled (and the 1967 pair will be up for sale). Given the space to keep them permanently and the time to do the work, I would go all out and dismantle the four speakers completely, put the electronics at the bottom behind each stack and mount all the electrostatic panels flat in a frame, which would then be very light and manoeuvrable indeed. There are various examples like this to be seen online – here’s a beautifully clean naked triple:

[/caption]
Reel-to-reel as the only source? That’s hard-core hi-fi…

Every plan for stacked (intact) Quads seems to show them with the lower speaker upside down, so that the transformers and connections are all together in the middle at the back.  I’m not sure why this is.  Trivially, it means short connecting cables, but so what? Quad electrostatics are vertical line sources, it makes no difference to the sound which way up they are. It does of course put the centre of gravity of the stack right in the middle – which would allow the arrangement to be pivoted about its centreline (as the HDQ stacks seem to be), so that they could be angled up or down as desired.  I can see the case for this, of course, though I don’t feel it’s worth the extra work: the line source will extend from floor to head-height anyway, and it would require making a frame for the speakers and another to hold it, and organising the pivot which would need to be very strong.

So unless some reader suggests a good reason for the base-to-base arrangement I shall have them both the normal way up.  The big advantage of this is that the centre of gravity of the overall stacks, which are going to weigh at least 50kg each, will be much closer to the floor, with consequently improved stability.  Also I shall be able to build something like a ladder, with the weight of each speaker resting on its wooden base on a crossbar.  I like this idea. 

If you really wanted to do it symmetrically, as far as I can see the weight of the upside-down speaker would have to be held up by screws running through the frame into its side-panels – which are only half an inch thick. I guess this would be OK with a fair number of screws, and the frame clamping the speaker tightly in place. A cross-bar (B1) under the metal mesh box that surrounds the transformers would provide greater security and rigidity overall:

Off with his legs

Right then, off with all the trim and legs.  3 screws for each side-strip and 4 for each foot.  72 screws in all….

Serial Numbers
Of the four ESL-57s here, two have consecutive serial numbers in the 19200s, which dates them to 1967.  This pair is a recent purchase, specifically for this project. They’re a bit dented about the grilles but, baby, those feet are like new.  The other two are 1975 vintage, with serial numbers 10 apart centred on 35500.  These have travelled the world with me, and been in regular use since I bought them in 2003 from someone in Luton who didn’t think it was safe to keep them with small children.  Their grilles were pretty much perfect for a while, but have now suffered slightly from being used to provide music for games of musical chairs – children 1, speakers 0 so far.

For reference, here is a list of serial numbers by date of manufacture – helpfully posted by someone on the Pink Fish Media forum.  I can’t vouch for its accuracy but it looks plausible:

1959 2000 – 4000
1960 4000 – 6000
1961 6000 – 8000
1962 8000 – 10000
1963 10000 – 12000
1964 12000 – 14000
1965 14000 – 16000
1966 16000 – 18000
1967 18000 – 20000
1968 20000 – 22000
1969 22000 – 24000
1970 24000 – 26000
1971 26000 – 28000
1972 28000 – 30000
1973 30000 – 32000
1974 32000 – 35000
1975 35000 – 38500
1976 38500 – 41000
1977 41000 – 44000
1978 44000 – 47400
1979 47400 – 50300
1980 50300 – 52100
1981 52100 – 52800
1982 52800 – 53000
1983 53000 – 53150
1984 53150 –

I was surprised when I got the older pair to find how different they were in colour from the 70s ones.  Their grilles are a darker and more golden shade of bronze, where the later pair are a paler colour, almost pink in comparison.  Obviously the vagaries of cameras and monitors makes this fairly pointless, but I’ve tried to photograph the difference:

The left hand side is a good reproduction of the later grille colour (on this monitor).  The older one is more yellow-gold than it has come out, though.

There are other external differences.  The wooden trim is darker in the later speakers, and both the side trim and feet have a different, slightly sharper profile.  The trim is also attached with different screws – shorter and apparently anodised a reddish colour to match the wood.  The earlier feet have a wooden dowel running up into the bottom of the speaker – this is missing on the later ones, which instead have some sort of metal bolt attaching the feet to their bases:

Despite these differences, both pairs sound identical, and in fact we’ve spent a couple of evenings listening to mixed pairs without any perceptible imbalance.  I’m not aware of any change of internal structure during the life of the ESL-57, apart from the EHT board being originally in epoxy and later in beeswax.  Nothing to affect sound.

Also, importantly for construction purposes, they are identical in overall size and shape:

In any case I’ll obviously be putting one of each pair per side, symmetrically arranged.

Time to get practical

Stage one.  Remove child and associated project from living room:

 

Stage two.  Take over. Who pays the rent around here, anyway?

Ingredients: 4 Quad ESL-57s; various bits of 4×2 and other lumber out of local skips (generally a higher standard than cut timber from a certain UK hardware chain); a couple of metres of extra speaker cable and a total of 8 banana plugs; several metres of mains cable and a total of 4 bulgin plugs; 8 castors capable of bearing at least 15kg each; lots and lots of screws.  Toolbox.

And then there were four

The advantages of stacking Quads vertically were recognised early in their career. It immediately improves the apparent bass, and as they’re a vertical line source you get the much greater presence of the larger area, without any compromise of the stereo image. This would never work with the later ESL-63 with its more sophisticated attempt to recreate a point source.

‘Another thing people like to do is to use two of our panels, one above the other. This is quite reasonable because it is really a strip source, you can extend the strip source without deteriorating anything. All you do is add 6dB at the bottom and 3 dB everywhere else. It gives you a louder sound, a more impressive sound. That’s all right.’

-Peter Walker in Audio Amateur, 1978

It’s been frequently attempted by individual enthusiasts and searching will bring up lots of pictures. The only commercial stacks I know of were part of the expensive ($30,000) Mark Levinson ‘HDQ’ system. This consisted of a pair of stacked Quads with Decca ribbon tweeters between the panels, along with two big Hartley subwoofers and several (6?) of Levinson’s heavy ML-2 25W amplifiers:


 

This rather grainy image shows Faye Dunaway’s stacked Quads, date unknown:

fayeDunaway_stackedQuads

They seem a bit close to the wall – and the whole room looks very shiny and acoustically reflective: I’m not sure they would have been at their best. Visitors probably gazed at her instead:

——————————————————————————-

Here are two interesting downloads on stacking quads.  For both of these links I am indebted to the most thorough and indispensable of ESL-57 sites online, www.quadesl.org

Double Quad”  T. Farrimond, Electronics Today International, 1975

Quad ESL Mods and Stacking” C. Beeching

And then there were two

Coincidentally, the first commercial stereo records appeared at the end of 1957.  Now two loudspeakers were necessary.

two quads 2

To have two makes them rather a dominant presence, at least in the average British living room.

Of course you could just have one ESL-57 paired with another speaker:  bizarrely, this was suggested in the original HiFi News review in November 1957, which concluded

It will not suit all tastes, but the reviewer can confidently recommend it as an excellent domestic speaker. As Mr. Briggs has recently demonstrated really convincing stereophonic reproduction with two completely dissimilar speakers, it is seriously suggested that one of the listener’s pair of speakers should be a full range electrostatic

Fortunately, the distinctive curvature of the panel and the perky angling of the little feet can do a great deal for spousal acceptance, if you are lucky enough to have a partner who appreciates 50s design.

quad-esl57-01
A certain style…

Unfortunately, stacking two pairs is going to deprive us of these positive elements, leaving something more like the monolith from 2001 – and even Dave Bowman only had to deal with one of them.

full_frontal_monolith
Do you prefer mono…

allenStackedQuads
…or stereo?

In the beginning there was one

‘Walker’s Wonder’  as originally intended, listening to the BBC in mono:


the classic ‘how it should be’ image

Note the chair, high enough for the stylish tilt of the speaker to aim it squarely at the listener. There was less slumping in soft sofas in the 1950s, and the speaker is aimed accordingly. I wonder if the chairs are from Heals – it’s rarely mentioned that Christopher Heal designed the ESL57’s woodwork. Once our man with the pipe gets the Home Service tuned in, you’ll notice that she gets shoved out of the sweet spot:

howItShouldBe_colour

If the two of them aren’t wearing synthetic fabrics they will be in a few years – and quite right too, since without polymers electrostatic loudspeakers would never have been possible.  The theoretical idea had been around since the 1880s, and patented at least since the 1920s, but early proposals to use paper or silk would never have worked: mylar film was the first material that could be made light, thin and taut enough to do the job.

ad_quadESL_november59