Greetings again.
To update my original post (1st Jan 2017)....... A friend confirmed what I thought - my system used to be good, but inconsistent. Now it is consistently brilliant. So what's happened ? A significant part of the turn around was good luck and chance rather than skill or intent, which is why I thought some of you might be interested. There's a lot of information to relay so I thought I'd update periodically. I'll start with my experience of smoke, floor and destructive bass.
Firstly, my Summits are the originals (not X stat) but I had new X stat panels supplied by Absolute Sounds and fitted by a local dealer. Although the dealer isn't an authorised ML supplier, the team, who'd had many years of experience working on many other brands including ESL's said they were some of the best made speakers they'd ever seen. The panels had to be replaced because I damaged them.
Smoke
Don't subject ESL's to smoke or fumes of any sort ! A symptom of smoke damage is dull sound. Vacuuming provides temporary relief and you can get away with smoke contamination a few times only, after which the damage is permanent. At the time I watched several You-Tube clips of 'washing' the membranes. I didn't think it was worth it as the replacement panels cost a reasonable £1,000 or so.
If you have a tendency to burn food in the kitchen, close the kitchen door and get an extractor fan fitted.
In the room the speakers are in... 1. Don't burn candles or incense. 2. If you have a stove, make sure its a good one that doesn't smoke. 3. Don't smoke.
I did all these things, ie bought a decent stove, fitted an extractor fan and banished hippies. The smoke contamination was the first factor contributing to the inconsistent sound.
Floor.
The Summits used to sit on spikes on an uneven quarry tile floor, the tiles themselves lying on a bed of ash (19th century cottage). Levelling was by spike adjustment. Using coins and other objects between spikes and floor destroyed the sound. I think there is a lot we don't yet know about the interaction of speakers and floor, a topic which I think is critical to good sound.
I followed the usual positioning and tuning rules, eg manufacturers handbook, flashlight, move 1/2 inch at a time, tilting and bass level controls, plus levelling due to uneven floor. I can only re-iterate what others have said and would add - Don't ever judge ML ESL's unless they are properly positioned and set up.
Destructive Bass
A problem I had two years ago was destructive bass. Bass notes were like a ton weight hitting the floor, no boom or bloom, just tight, fast, pile driving bass. You could feel the bass as well as hear it but it came more from the floor it seemed than through air. The energy would project along the tiles and up the body of the seated listener, like an electric shock. I often had to warn people before turning the volume up. It was exhilarating to some, frightening to others. Summits, I've been told are not supposed to do this, but they most definitely do !
This was fine except that with the volume loud... 1) The speakers gradually moved along the floor (the second factor contributing to the inconsistent sound) and 2) plaster would fall off the wall and ceiling from the back of the room. The system was destroying my house !
The Summits are now standing in their original positions but with spikes removed atop Townshend Audio Seismic Isolation Podiums. These, although expensive for what they are, have the effect of ameliorating the bass. It's still there but it's not as destructive. You now feel it less through the floor and more through the air. However, the tamed bass is compensated for by an even clearer, more transparent and focused sound. Detail retrieval is better but all the fun and timing and musicality is still there. The Podiums are definitely having a beneficial effect. And my house is still standing.
More to follow.