The illusion of soundstage.

Sidewalls were (and still are) about 6 feet on one side and the 1st reflection point on the other side doesn’t exist since there’s only 3 feet of the side wall extending out from the front wall before it gives way to being open to the rest of the house. I have only owned monopole speakers, but I really noticed that a portion of that uber-wide effect wound up being curtailed just a bit once I switched from that DAC to a (overall better) CDP. That DAC was good at scrunching up the soundstage toward the zone in front of the speakers...something I was not really shooting for, despite its own advantages. (If you’re into the very forward presentation thing, that DAC probly would’ve sounded great with a Grover Huffman loom!...DAC is an EVS-modified Behringer DEQ2496).

If you put your drivers out of phase with each other you will get sound all over the place. Q-Sound is software that manipulates phase to put sound beyond your speakers , even behind you
Alan

Or, in my case and situation, I'm running Walsh drivers which are omnis.  I've a 'soundstage' that 'extends' not only to the sides but also in front and behind the drivers.  Placement within the given space and the surrounding objects (or lack of same) will certainly effect 'the effect'.  I've also noted that from selection to selection, artist to artist, album to album there's distinct differences in what is perceived where.
Adding a second pair, either in 2 channel or 4 channel arrangements, and playing with delay or no, you can be sitting 'on stage' or row 5....
But 'immersion' isn't to everyone's taste.  To each...

I think a wider soundstage is a result of proper setup for I have yet to hear a pair of speakers that do not pass beyond the drivers. Ex: with Dyn's I found very little to no toe in extends the soundstage way beyond the speakers and still retain great imaging but somewhat close to each other. Toe them in and the imaging gets a hair better but looses the wide soundstage. Raidho/Scansonic on the other hand require a farther distance apart but with a fairly severe toe in. No toe in creates an even wider soundstage but then severely looses the imaging.

Pan pots used to any degree by any recording engineer are the secret…pan left, pan right, or no pan at all.