Soundstage and image height, does it exist?

Image height is a function of the reproduction chain, loudspeakers in particular. If it was simply a matter of saying that there is no vertical information encoded in stereo recordings then the resultant sound stage would be non existent in the vertical plane.

This first time I heard height reproduced through a hi-fi system was when I played Boult's recording of Holst's The Planets (EMI ASD 2301) on a Thorens TD-125 Mk.2/SME 3009/Decca Blue pickup turntable, feeding pair of Magneplanar Tympani T-I's bi-amped with ARC tube amps. Way, way at the rear of the hall (which itself could be heard) I could "see" the percussion instruments (particularly the triangle), raised on a podium above the instruments in front of them. I didn't yet know symphony orchestras were so situated, and had no expectation to hear that sound. Yet I did. 

@roxy54 --

With speakers I guess it’s all about the way the drivers disperse the sound.

+1

I like that the actual, total radiated field of sound extends somewhat beyond the listening height (with a line source ideally terminated at both the floor and ceiling) dictated by ear level above the ground. My own speakers are just above 6 ft. tall, but the acoustic center at the LP is situated between the upper edge of the bass bin and the lower edge of the horn above (i.e.: at 100-105 cm’s). This way there’s a sensation of what’s presented to the ears as being less restricted and more immersive (or fuller), and so there’s a larger "canvas" for the sound to emit itself from. Physical properties of sound that to my ears more closely emulates the signature trait of an acoustic live symphony orchestra concert, or even a live amplified one.

Whenever imaging or soundstage are mentioned, I like to remind people about these resources: The following provide tests, with which one may determine whether their system actually images, or reproduces a soundstage, as recorded. ie: On the Chesky sampler/test CD; David explains in detail, his position on the stage and distance from the mics, as he strikes a tambourine(Depth Test). The LEDR test tells what to expect, if your system performs well, before each segment. The Chesky CD contains a number of tests, in addition to the LEDR. (https://www.audiocheck.net/audiotests_ledr.php) and (https://www.amazon.com/Chesky-Records-Sampler-Audiophile-Compact/dp/B000003GF3) The shape of your ears’ pinnae is also a variable, regarding your ability to perceive images/locate sounds. A Stereophile article, that explains the LEDR test: http://www.stereophile.com/features/772/  

To quote Bobby Owsinksi from The Mastering Engineer's Handbook:

The LEDR test is a substitute for about $30,000 to $40,000 worth of test equipment.

Stereophile also has an article about it, written in 1989 (!) by Bob Katz:

"My system has great imaging!" "I can hear sound coming from beyond my speakers." "The depth image in my system goes back at least 20 feet." Yes, we audiophiles are proud of our imaging (footnote 1), and we've worked hard to get it. My back is still aching from the last time I tweaked my speakers until the image was just right. Wouldn't it be nice if we had a test to set up and check a stereo system for correct imaging? Yes, Virginia, there is an imaging test—your LEDR is here (footnote 2). LEDR, which stands for "Listening Environment Diagnostic Recording," is available on a test CD from Prosonus, the Studio Reference Disc (footnote 3). The CD is rather expensive (about $50), but there is no other official test for imaging. [Since this article was published, an LEDR track was included on the first Chesky Records Jazz Sampler & Audiophile Test CD (JD37).—Ed.]

Luckily it's 2022 and we don't have to buy expensive CDs anymore, as there is an online version of this test here: http://www.audiocheck.net/audiotests_ledr.php

The Stereophile article has a rather lengthy explanation about what you should hear - the short version again quoted from the Mastering Engineer's Handbook is:

If the sound for the up image doesn’t go straight up from your loudspeaker, six feet in the air as you sit there in your position, then you’ve got a problem with your crossover or with reflections above the loudspeaker.

If the sound doesn’t travel from left to right evenly and smoothly with the left-to-right test, then you’ve got problems with objects between your loudspeakers.

And the same with the beyond signal, which is supposed to go from about one foot to the left of the left speaker, gradually over to one foot to the right of the right speaker, which detects reflections from the side wall.