I haven't voted yet, as I'm not sure I can pick one, but I'll think about it as I write. To me the soundstage can vary depending on my absorption level into the music and my mood (I don't do drugs by the way beyond relative occasional alcohol and daily caffeine), and is also heavily dependant on the headphone in question as well as the tracks being played. With my best soundstage headphones which are K702 and HD560s then on the right tracks and right absorption level of me into the music then it can feel 3D - with some effects circling my head front to back & left to right, with the K702 showing a wider soundstage than my HD560s, but HD560s images more precisely in terms of smoother panning and more finegrained ability to pick specific angles of direction - for instance when 3 people are singing on one of my tracks it's a lot easier with the HD560s to place each of the 3 singers at consistent slightly different angles to each other. I also have found that after I've done a session of Virtual 7.1 Surround fps gaming (where I use sound heavily to pinpoint 3D directional positions of enemies) that afterwards I'm more sensitive in detecting changes in the image & soundstage created by headphones when listening to music in headphones - and it seems more expansive & realistic. I think there's a large element of mood/absorption/"training" in how the headphone experience unfolds, combined with the inherent soundstage ability of the headphone in question and of course the track being listened to.......and of course the EQ, to me the best soundstage EQ's are literally the EQ's that sound the most balanced to me, which is always some take on the Harman Headphone Curve - I think it's important to have a balanced frequency response where nothing is pushed too far forward into the mix, so that you can let your mind flip between the different elements/instruments of the track you're listening to - so I think that enhances soundstage ability of the track in question. Right Headphone / Right EQ / Right Mood & Absorption / (Right "Training") / Right Track.
I'll think about which option to pick in the poll.....I voted "Full 3D Image" but that's mainly at it's best (most optimistic) and only with a few specific effects within a track (like electronic effects in a track that might have been designed to sound like they're looping around your head as it pans from left to right and back again), it's not like there are specific instruments or voices located permanently behind. Otherwise I would have chosen "Slightly In Front of my Head" or also added my own new option in the poll of "In my head for centre, out of my head for left, out of my head for right" - and I tend to flip between all of those mentioned votable options depending on any combination of the stuff bolded in the previous paragraph.
EDIT: I wouldn't mind being able to pick more than one option in poll, because it varies.
EDIT #2: There can always be some kind of depth associated with listening to a piece of music, it's easy to imagine particular singers are further away or closer to you within a piece of music, especially when more than one singers are singing, and even more so when it's the same singer but they've got say 3 seperately recorded tracks of themselves singing at the same time. But, that's a bit different to what I was talking about earlier re occasionally having the sensation of some effects coming from behind you as they pan around the soundstage.
EDIT#3: I have to close my eyes to properly picture the music as if I leave my eyes open then that disturbs the process - to me soundstage of a track be it through speakers or headphones is a very visual experience, and having my eyes open disturbs that (less so with speakers though).
