Well, after a bit more work, the surround is now firmly attached to one bass driver, which has been returned to its cabinet with the benefit of a new airtight gasket.
I've been playing CDs with the preamp set to mono and the balance control swung over to one side for the last few hours. I got the 50 watt Levinson amp connected to it and started off at extremely low volume.
First impressions were of a very thin and weedy sound but after half an hour or so and with progressively more power running into it, the sound began to fill out.
It is now sounding absolutely superb. Even in mono, it's very easy to see how the LST was recognised as an outstanding device in its time. Makes you wonder whether there's been any real progress in loudspeakers since the 1970s.
Wow!

I believe all of them from this period were true IB's.

My own take on whether speakers have really improved in recent decades is that of high quality available for low cost. I'd say all sub £200 speakers sourced from China just couldn't have been made so cheaply back then. I mean, AR7's were around fifty quid the pair back in 74 or 75 and they were cheap. That would have to equate with around £300 the pair now as an absolute minimum I reckon. Costings are different now, but the distributers are the ones making huge dosh. I remember a Sony cassette deck we liked, the TC186SD. It sold for around £120 in 1974 pre the huge VAT rise. The dealer paid around £80 for it and maybe discounted it to £110 or so, but ex-works in japan, it would have been around £25 I was told. In the early noughties, I was also told that Quad 11L's came to the UK landed cost at $14 the pair, ready to ship out to dealers for around £200 or so. I can't prove these figures, but even recently with inferior exchange rates,, some M-Audio mini-actives which sold for £330 or so the pair reportedly came in for £60 or so.

I appreciate that AR had to make their speakers over here in Houghton Regis for prices to be competitive - did the LST get made here too I wonder? - but parts costs would have been much higher, although by the late 80's, the effect of cheap far eastern voice coils at tens of pennies or so each on an egg tray were starting to filter through..

That's what I said?

Oh!

Turning my mind to how these speakers will be used, I've been pondering the subject of stands for them. They're a really tricky proposition to find a suitable stand for because of the combination of the odd shape and size and also the low height. Then, when you consider the weight we're dealing with, you realise it's not going to be straightforward.

Dimensions: 68.9 cm (w) x 50.8 cm (h) x 24.8 cm (d)
Weight: 40.5 kg

The height for a pair of stands seems to be about right when you put one on top of another, so that's a start but this puts the centre of gravity quite high, so they'll need a big footprint. The only thing that comes anything like looking appropriate to me is a couple of centre speaker stands, with lowish height and wide top plate and base.
However, I'm thinking of having a pair of wooden stands made by a local woodworker, so I'm wondering about a suitable design.

AR used to supply a wooden stand and good quality modern copies are available but I don't think they were intended for the LST at all.  I think they are too low, perhaps not really strong enough and I suspect anything other than a box with 90 degree corners will look rather silly on them.



There's not much else in the way of inspiration on the web, but something like these seem like they might work OK.




I'd love to hear any thoughts and suggestions.  Example images are good too!

That would be the thing, wouldn't it?
The pair on the stands in the images above are for sale at the moment. I'll take those - a piffling US$4,238.00!

Hmm, that's not something I'd considered at all.
Not sure how it might go together. Brain cells engaged and beginning to whir around a bit.
Thanks for the thought provoking suggestion.

What about a glass equipment stand like I use for my setup? Looks the right shape,height might be ok and it'll take the weight. I can't post a pic just now but you'll see it in other pics of mine.

No problem at all - just hope you find something that suits.