I'm afraid earspeakers doesn't know what soundstage is. He thinks headphones that are open or closed have different soundstage. He doesn't understand that soundstage deals with precision of sound location, both in physical and simulated space, not the general "openness" or "width" of the sound. If he made an attempt to understand what people say to him instead of ranting and throwing insults, he might learn something.
The problem is that audiophools grabbed onto a real technical term, "soundstage", and gave it a vague, woo-woo definition of their own. They use it as a flowery term, like "veil" or "blackness" or "speed" to describe the way they feel about sound without fully understanding what is causing it. Then people took that definition and tried to think of a reason it might be so... open/closed, ear pads being hard or soft creating reflections, ear cups as tiny rooms... All of that is hooey. Headphones are open or closed sounding. Varying the angle the sound shoots into your ear can make a difference. But none of that has anything at all to do with soundstage.
Soundstage is a flat plane of sound ten feet or more in front of you where sound objects in the mix can be placed anywhere between the speakers from left to right. To the listener, it sounds like sitting in an audience and having the musicians sitting on a stage in front of the listener performing. You can point to the vocalist in the middle, the piano slightly to the left and the guitarist on the far right. The guitarist can walk across the soundstage to the left of the piano and you can hear him move from right to left. Soundstage is part and parcel of stereophonic sound, and it is designed in the mix.
Poor soundstage has dropouts in the middle because speakers are too far apart. Things feel like they are just left and right with no meshing between them because the speakers are positioned incorrectly in the room. When I was a kid, I had a few friends who were audio nuts. One of them saved money for years and assembled a McIntosh system. He bought massive Altec Lansing speakers and put one on each side of his bed facing towards the middle. He said he was trying to make it "like giant headphones". Even lying on his bed, the sound still had no definition in the middle because the speakers were opposite each ear, and the bed was acting as a huge sound damper right in the center of the soundstage. Over a three day weekend, I finally convinced him to move his room around to put the speakers parallel with a single wall, and his bed along the opposite wall. I told him if he didn't like it, I would help him move it back to the way it was. "Fun experiment. We've got the day off from school, why not?" He skeptically agreed. It took a lot of work with moving dollies because those speakers were the size of big freezers or washing machines. When we had everything in place, he skeptically flicked on the sound and sat on the bed. It was like night and day. Now there was a clear aural image in front. His room was still way too small for those speakers, but at least he had created the proper triangulation between speakers and listening position. I didn't have to help him move the speakers back.
If you are used to having the sound enter your ears straight on, you don't realize what you aren't hearing. Putting the speakers at the recommended distance and angle creates an aural image with specific sound location. And the secondary distance cues (reflection, reverb) are designed in the mix to work with that image to create an illusion of depth too. With headphones, it's a straight line through the center of your head and you have no idea what people are talking about. Some people listen and learn something new. Some people argue from ignorance and just get mad. (Dunning-Krueger). I try to not get frustrated and patiently explain things. Maybe someone else will get value out of what I'm saying. I appreciate it when people teach me things with patience.
I dunno maybe soundtage is the wrong term? Maybe "perception of width" would be better suited. That's just semantics though. It's all the same thing.
The terms I use are:
Headstage: That is the straight line extending through the center of your head that you hear with headphones. It can be more open or more closed, giving the illusion of sound seeming wider or narrower.
Soundstage: As I just described
Soundfield: A three dimensional soundstage that extends from the front of the room to the back (or with Atmos, from the floor to the ceiling too). This is what you get with multichannel speaker setups. The precision of the placement of sound objects within the field becomes more defined as you add more speakers in an array. Soundfields can alter the perceived size of the listening room and simulate everything from cramped, boxy sound to wide open sound like standing in the open air. Listening position, balances and room treatment can be critical to the effectiveness of soundfields.
Soundfield > Soundstage > Headstage > single sound source (mono)