Not seeing the sound

Check the phase - out of phase speakers have sound coming out of nowhere.  Put on a cd with a well-centered vocal like Nora Jones and make sure she's coming from dead center.  If not, your speakers are out of phase or you moved them to such a wacky position that there's no imaging.  Soundstage denotes the illusion of the musicians spread between, behind and in front of the speakers, but everything should be identifiable in terms of location, IMO.  If you can't tell where the performers are, something is probably screwed up.  

In addition to chayro's description of a phase issue, you most likely will experience a loss of bass impact. If all the instruments/musicians are positioned in the right place and your imaging has width and depth with good dynamics, then you have found your soundstage.

Yes, the musicians are positioned in the correct places, and vocals come out dead center. So, I don't think the speakers are out of phase. I believe I may have found an audiophile unicorn.

I call this "not hearing the speakers"

Meaning, when you can no longer hear that you have distinct boxes making sound but instead perceive the illusion of sound events coming from a number of places.

Good speaker placement and acoustics matter a lot to make this happen.

When you see the phrase "disappearing act" or "the speakers disappeared", this is what they mean. You hear the music, however, if you close your eyes you don't hear the music coming directly out of the speakers. This is a key audiophile attribute IMHO. If your speakers sound good tonally, have frequency response that is high and low enough for your taste and they also disappear, you've officially got yourself an audiophile system!

Enjoy it........