Soundstage Width and Depth

Ambiphonics:  I would start with this:   https://cdn.website.thryv.com/7b2b654758d449b08935c9dfa207e8f9/files/uploaded/Ambiophonics_Book.pdf

Then read this article on methods that are more robust:  https://www.microsoft.com/en-us/research/wp-content/uploads/2013/10/Ahrens2013a.pdf

While there is criticality of listener position, it is much more robust than ops "fluke" that requires perfect everything to "maybe" work.

There a couple of Stanley Clarke tracks that are just electric bass and Gregory Hines tapping for percussion. You can feel the size of the stage and follow steps he takes.

Another track that never fails to amaze me is by The Propellerheads and starts with a skateboarder. While I fully expect to hear the panning back and forth, hearing the depth of the half pipe below my floor is always a surprise. I kinda get how speakers can sound forward or laid back, how the soundstage can extend beyond the speakers left or right, but up and down is mystifying.

The real question should be about soundstage width and depth that exist but shouldnt. Exactly how much of these characteristics are the result of speaker placement and how much is actually on the recording? 

audiokinesis
@geoffkait wrote: " The best and easiest way look at soundstage imho is that the better the output signal the larger the 3 dimensional sphere of the recording venue will be presented.”

I’ll concede that what you propose is the "easiest" way to look at soundstage, but I’m not sure it’s the "best" because it is incomplete. Neither does it tell us anything about how or why, nor offer guidance as to how we might make improvement.

>>>>>OK, fair enough. Here are some ways to improve the soundstage, in terms of expanding the 3 dimensional sphere and organizing and resolving the information within the sphere. There is no substitute for Signal to Noise ratio. All of these suggestions improve SNR - including for the signal in the room. I am not going to address information fields or mind-matter interactions, which are also important factors, as they’re beyond scope.

Here is my short list of how to obtain deeper wider higher and more resolved soundstage. This list is not meant to be all inclusive.

Isolate all components
Suspend or elevate all cables and power cords
Position speakers precisely using XLO test CD or similar Test CD
Address room echo and room corner SPL peaks - I.e., comb filter effects
Cryogenics and/or home freezer for anything that you can fit in there
Address static electric fields
Check electrical continuity/polarity
Clean all electrical contacts, including all wall outlets in the house
Address RFI/EMI
Address vibration of the CD itself, or cassette for that matter if you’re into the whole cassette thing.

Duke,
w.r.t. your sensation of height with that speaker set, been thinking about it more. I still feel there was the potential for frequency filtering (and possibly reflection/sheltering) due to the microphone pattern and position, and this could have simulated a human torso / ear / pinna. Being line source, there would be limited ceiling and floor reflections, so what got to your ears would have limited room interaction from a height standpoint preserving what was in the recording. Again, interesting. Been checking the local classifieds for a tolerable line source speaker to do some experiments.