Generally speaking if they are tucked inside your ear canal, such that the natural reflections from you ear lobe come into play, that's a binaural recording, and it's been said many times that recordings like that sound great with headphones but not great on a big stereo. I've never actually tried it, I'm just spouting urban legend. I would say that is the extreme example of no open space.
I have some DSM-6 omni mics which hang off my glasses. I've run them back by my ears, and I've run them forward a bit more, about even with my eyes. I think they sound better when I move them forward near my eyes. It sounds a little more open, and a little less muffled. I suppose that would be the example of "a little open space".