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:
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: