I thought 3D sound came only from the tweeters, but it seems that long bass waves have somehow spatial information that contributes with imagin. Incredible!
While we don't hear low bass frequencies as localized sounds within a sound stage the way we do upper bass, midrange and treble, really low bass does contribute to imaging by imparting a sense of space. Really good low bass like you get with the Swarm or other distributed bass array can put you more fully in the recording venue. This reviewer explains it beautifully. http://www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/
There is more to what is going on here than just the perception of what is happening in the music itself. There is also a quite startling spatial effect. We are all accustomed to being able to control room effects in the mid and higher frequencies by acoustical treatment. But this is harder to do in the bass, and in most rooms there is a definite residue of spatial signature carried in the lower frequencies. The bass is one of the main ways you sense the size and shape of the room around you, and typically the signature of the recording venue is overlaid or even swamped by the bass signature of the listening room.
But the Swarm, presumably because of its smoothing out of response, largely suppresses the bass signature of your listening room. And as a result one can hear the original venue in a most unusual way. I played in a performance of the Sibelius Second Symphony recently, so I was particularly attuned to the acoustic effect this piece makes in a concert hall. Listening to Berglund’s recording for EMI with the Swarm in action, I heard a remarkable facsimile of the size and envelopment of the actual symphonic sound emerge. At the end, I felt like standing up and cheering, so close did I feel at some basic level to the real experience.