Is soundstage DEPTH a myth?

I listen to Classical.  I define depth as when I can clearly tell the percussion are located to the back and stage left, the brass to the back and stage right, and if the conductor divides the violins I can easily discern that.  Also if one gets the feelings of the spaciousness of a concert hall, as many orchestral recordings are now live

+1 @mahler123

On the cut, ’My Name is Robert Neville’ from the original movie soundtrack, "I am Legend", the opening trumpet sounds like it’s coming from my neighbor’s house across the street - to the right of center.*   With lesser quality cabling and/or removing the power conditioner, I can make the sound stage flat as a pancake - without changing anything else.

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Similar but not as deep with: 'Fanfare for the Common Man' - Minnesota Orchestra - Copland.

I have "depth" throughout the soundstage - up to the left edge of the left speaker and the right edge of the right speaker.  I have width beyond the speakers but there doesn't appear to be much depth beyond the edge of the speakers.

The depth of the soundstage is determined by your equipment, venue, and recording. Assuming a good recording that can have depth… many. I don’t want to get off onto the details of this subject.

My system images well (see mine under my UserID). When I finished up positioning the speakers the soundstage would extend two or three feet beyond the speakers to the side and back about 4.5’ to the wall. Then I hung a very heavy tightly woven wool carpet on the wall… now the soundstage goes back into the wall two to four feet more depending on the recording.

In previous systems, initially the soundstage only extended to the wall. Then, upon careful tweaking the wall ceases to truncate the soundstage depth.

Many years ago, I was fortunate to run across a local audio store owner who was much more of a hobbyist than a businessman.  I had many discussions and spent may happy hours of listening and more importantly, learning in his store with him and his customers. Over the years, I learned a lot about different music and systems and especially how to listen with the moving in and out of components and the varying differences that resulted and were perceived.  

You can't learn by only talking about it.  Listening to multiple systems and components (plus discussions about same) do help.  That's why the Chesky Ultimate Demonstration Disc is a good one to own.  Because each track is prefaced with a description of what should be listened for and then what should be heard.  Even then, the results are obviously system dependent.  Just because you think you heard it, you may not have heard it, like it really could be heard and experienced!

For example, many years ago, I used the Superman track on a Telarc disc as one of my auditioning pieces.  I had occasion to go to an audio store to listen to some used Apogee Stage speakers that I was considering purchasing.  The speakers were good, but what struck me was the finale of Superman and its crescendo.  It wasn’t the speakers that blew me away (they were great too) but the amplification.  The drive separation and coherence of that crescendo was what I had been seeking, but didn’t know it until I heard it.  In fact, when it finished, the salesman saw the look on my face and asked what was the matter?  That and a test drive later of an Audio Research VT100 Mk2 tube amp taught me how important great amplification was.  Before then, I didn’t want to believe, because my wallet didn’t want to believe that my Aragon  4004 MKII amp was not capable of the performance that the Audio Research was.  I found that not only was the Superman ending crescendo more powerful with the instruments more delineated and overall, more open, and less congested; but instrument like woodwinds and brass sounded more like live ones, the sound I was seeking but didn’t know it, until I heard it! 

My point in saying all of this is to suggest again that you don’t know it, until you hear it and you generally can’t hear it by sticking to a this or that component.  You must try as much as you can and as high of quality as you can.  Otherwise, learning can’t take place.