Is soundstage DEPTH a myth?

ARC Hardware + Magneplaner speakers.  Good source recordings.  Try Sheffield direct-to-disc for an example

YOUR ROOM has to be conducive to music reproduction accuracy.

Cheers!

It has to be a live recording to have true soundstaging.  Studio recordings may have soundstaging, but it is something manufactured or mastered into the recording, as studios are usually inert.

Much of what sense of depth you perceive has to do with how a recording was made. 

We hear with two ears that are for all practical purposes are the same distance from the front of the stage.  They are also the same distance from the rear of the stage.  The space between our ears accounts for the difference in arrival time as well as the difference in intensity of sound reaching each ear.  This works very well in helping us locate (left to right) the source of sound.  What helps us differentiate what sounds are coming from the front of the stage vs. the rear, is the proportion of direct to reflected sound as well as the loudness.  In a concert hall, the closer we sit to the front of the stage, the greater the difference  we will perceive between strings and woodwinds as an example.  When we sit more toward the back of the concert hall, the greater the amount of reflected sound vs. direct sound reaches us and so the depth of the orchestra gets flattened out. 

So back to how a recording was made:  If many microphones are placed throughout the orchestra, not only will the sounds of say, the horns reach their mics at the same time as the sounds of the strings reach their mics, the pickup of each of those sections will contain roughly the same proportion of direct vs. reflected sound.  While it is possible to delay signal coming from mics toward the rear of the orchestra, there is not much that can be done to alter the proportion of direct to reflected sound in any sort of a natural way.  This is why these kinds of recordings sound so flat from a depth perspective.  It's kind of like a cardboard cutout of an orchestra.  Everything sounds intimate, but not anything like it sounds in a concert hall.  If you listen to very early stereo recordings made by Lewis Layton or Bob Fine for RCA and Mercury respectively, you will hear all the natural depth of the orchestra from the best seat in the house.  Why?  They used only two or three mics and placed them very carefully.  Many of the Telarc and Chandos recordings were made using similar techniques.

Recordings of rock and jazz and pop music are typically (not always) made using close mic techniques.  Seven mics on a drum set is not unusual.  Very intimate sound, but nothing approaching natural sounding.

@dinov Spot on. After a bit of upgrading (more than a bit) I could have sworn all of a sudden music was playing behind as well as in front of my listing chair. That's the very definition of holographic soundstage. 

Soundstage depth mostly depends on recording and mixing quality rather than your equipment.