Most LS3/5a owners will scream if supertuning them is suggested and if you want to try "upgrading" the crossover components or internal wiring then you are pretty much on your own.
But there is one tweak which you could try. It costs almost nothing and can can make a huge difference to the sound of your LS3/5as.
I found out about it when I was told about the "Box Test".
I was contacted by someone who used to work at BBC Research Dept at Kingswood Warren (KW) during the LS3/5a days. He gave me the following details about "The Box Test"
"Do you know of the box test? At KW they used to test the integrity of the box as a whole by gently pressing the bass unit inwards (towards the cabinet). It should move slowly and with some difficulty, as the box equalises to the compressed air. On release it should move back outwards to its rest position slowly, almost reluctantly. If it moves out quickly (or instantly) you have a sealing problem. Happy days. I mention this because many KW people thought it to be the critical factor - the boxes that did best on this test tended to sound best (taking for granted that eveything else was to spec.)"
It was suggested to me that from time to time the seals should be checked using the Box Test and if necessary the cabinets be undone and resealed. Plkasticine was suggested as a good sealant.
I tried this out on a pair of my own Chartwells. I first performed The Box test and noted the behaviour of the B110. I then removed the baffles and inserted a fillet of Blutak right round the cabinet so that when the baffles were screwed down again the Blutak would make an airtight seal. In order to ensure that the screw holes remained airtight I arranged a "D" shaped piece of Blutak around each screw hole.
The baffles were then screwed back on, working round and round the screws and tightening each a little at a time. The screws need to be tight but take care not to overtighten and strip the threads.
When I tried the Box Test again the B110 moved outwards much slower than before, taking 2 or perhaps 3 times longer to return to the resting position.
It is early days as I write this but the change in sound was very pronounced. I was prepared for the speakers to sound more controlled (which they did) and for everything to be tighened up. But the greatest improvement, and one that suprised me, was to the stereo imaging and soundstage.
Warning! You do this at your own risk. It will be hard to get the baffle off again if you use Blutak as a sealant and it would be very easy to slip and put a screwdriver through the driver. Take care!
Supertuning the Crossover
Some of the LS3/5a enthusiasts at BBC Kingswood Warren considered it worthwhile optimising the crossovers. This was done by using a high- accuracy measuring bridge to check the value of crossover components, especially the capacitors. Closely matched components were selected and where required were finally brought up to correct value by adding small values of C in parallel.
The aim was to bring the crossover component values as close as possible to their theoretical values, and, to ensure that two LS3/5as in a pair were very closely matched.
This kind of time consuming adjustment simply wasn't feasible for the manufacturers of production units which consequently exhibit a much wider spread.
I understand that units tweaked like this are audibly better than "off the shelf" production speakers.
I'm absolutely not suggesting replacing crossover capacitors with highly-expensive esoteric audiophile grade components with some kind of magic properties! I'm suggesting a tweak, I would rather call it an optimisation, passed on to me and which is based on sound engineering principles. For an enthusiast with access to the right test gear, and a good selection of caps it need not be expensive.