Excellent write up Alan and a most interesting read.

I too use Quad 57s and have tried/experimented with augmenting the bass performance with a subwoofer. Sadly I didn't get on with it, particularly finding the correct level was impossible to set: either it would be too high and the bass was intrusive (roll-over set to 40Hz), or it would be too low and there was no overall contribution. It also varied depending on what was being played. Maybe I should have persevered, but the sub was loaned to me, so I didn't have a lot of time to 'optimise' things.

What are the super tweeters you are using Alan? What is the crossover frequency?

Talking of "How hi ?", are you still hanging the Quads from the ceiling? I think I can see the suspension hooks.

Anyway excellent work, well done.