Is soundstage just a distortion?

Csontos, could you say the same thing about the difference between tubed and solid state stuff? Think, coupling digital and ss could be a perfect combination for 'definition', 'resolution', etc. Or not. :-)

Note that when you listen to your system 'out of phaase' that while the sound may extend beyond the sides of your speakers that it also looses center image specificity. This is not a 'distortion' as such coming from your system or the recording. Some folks refer to the sound as 'phasy' and in the old days some audio stores (when you had them) intentionally set up some speakers 'out of phase' knowing that it creates the impression of big soundstage which could impress a beginner who would buy, take the speakers home and set them up 'in phase' and then wonder what happened to the big sound he heard at the store.

When your system is 'in phase' you will maximize its ability to produce a holographic soundstage, only limited by its design and set-up.

Unless your recording has some out of phase sounds in it, and many do (often intentionally put there I think for its effect - you get good specificity and the out of phase information makes it appear huge), you should have no sounds appearing outside the space between your speakers (on the plane of the speakers).

FWIW, multichannel sound effects -artificial though they might be, can be had on the cheap by putting 2 small speakers on the rear side walls of your listening room powered by a seperate amp and attenuator out of phase with the main system. I believe they called the a Hafler system. Not all that good really, but a very interesting thing which can be addictive if you are not really all that fussy. The whole room seems more energizied and the sound stage collapses when you turn off the small rear speakers. There have been many, and some very expensive, audio components developed expanding on that simple Hafler thingie.

Hope that helps you understand this subject a bit more. BTW,

FWIW, I like Almarg's observations regarding ceiling (room) reflections of the very high frequencies as being a possible issue contributing to the illusion of height. I would add though that I think the volume (SPL's) might be as great a contribution as well.

At least this was my experience with QUAD 63'S a number of years ago, not so much today with my present stuff. I think this is because of the vertical dispersion differences between the speakers. (My present tweets are Dynaudio Esotar's).

FWIW.

Al's comments are on point. Goeff's reference to the Opus 3 recordings, especially 'Depth of Image' makes me wonder though what would have happened if I had never heard that record over a system which had its soundstage capabilities optimized. I used this disc for years as a goal/reference when trying to establish my own system. But, if you had never heard its capabilities in the first place it wouldn't mean so much - it still sounds great and you might not know what opportunities for improvement exist.