OK Al. Let us just take your definition of space and how it relates to Karen’s definition in the context of this very thread. If we can start there, would you mind sharing your opinion of her comment about how to achieve that “space“ from an audio system in a listening room?
In her opening post Karen talks about the ambience and scale of the original recorded space.
As I said above:
"The space of a performance should expand dramatically if going from intimately recorded chamber music to large orchestra in a large hall.
"Yet the ambience of that concert hall will differ dramatically from that of an equally sized stone church."
While the space of a performance should expand dramatically from small to large on a system, in most home situations this will be a a relative expansion. Few systems will be able to portray something like a real scale of an orchestra, and the success of that illusion will also depend on where you would sit in a hall (if you were to sit close to an orchestra, in one of the first rows from the front, the scale might seem so large in width that it would be rather impossible to reproduce that in a home setting).
In my estimate a room of around 20 feet wide can at least hint at a real orchestral scale in reproduction. In my 12 feet wide room this is obviously far from achievable (bigger speakers would not make much difference there). Yet as you noted the last time you listened to my system, it portrays very different scales of recorded space and performer images (also depending on close-up or more distanced projection) from recording to recording. I like this too, but this is relative scaling; to me space has an absolute size component as well. As you have also said on several occasions, my system can sound quite big, but that is still not big enough in absolute terms for some music.
My system can reproduce recorded acoustic ambience of a concert hall, and it can reproduce the stone church acoustics in some choral music, for example. Yet this ambience is scaled to a smaller size, it misses the absolute scale of the real thing. But the ambience is no less real than if it were portrayed to a larger spatial scale in the absolute sense. So there is a difference between ambience portrayal, which can be scaled down in space to some extent without necessarily losing credibility, and the portrayal of absolute scale of space.
Therefore, I simply do not think that the terms of ambience and space describe the same thing. There is a scaling factor that does not apply equally to both. Also, you can get space (scale) without sufficient ambience.
As Brian (Bazelio) put it above in stark terms:
"Right, and I've heard space without ambience and ambience without space."
(I would say you can get some limited ambience on a table radio too, for example some portrayal of a church acoustic, without space.)
And as I have argued above, presence is yet again different.
As for how to achieve space -- certainly spatial depth -- and ambience, that is made possible by two factors, the minimization of acoustic noise and of electronic noise.
If a room has too much self-noise in the form of lots of uncontrolled reflections, it will suppress space and ambience from the recording -- it may flatten spatial depth and deaden recorded ambience or, conversely, create fake spatial depth or "ambience" on almost everything, rather independent of individual recordings and overruling information on them.
Similar holds for electronic noise in the system (starting with power delivery and power supplies within components), since that noise will suppress low level information about spatial depth, ambience and decay.