I don't claim to be able to give that but there could lie the answer why some agree there's stereo and some don't. If it's a perfectly planar wave front (if you can make them) we won't hear any stereo effect at all. The conventional systems make spherical wave fronts and linear arrays such as BCs make nearly cylindrical wave fronts. Though relatively slowly, volume does drop even with Bose sticks (nearly cylindrical wave front, energy density drops roughly 1/r compared to 1/r^2 in spherical). Volume won't drop if it were a planar wave front (something like a laser beam but the sonic form).

So, we are somewhere in the middle (stereo as we have used to perceive with spherical wave fronts and planar where we won't have any stereo). Some tend to project it to one end and the others to the other end.

Theoretically, with Bose sticks, I find it hard to imagine there's no stereo at all or there's stereo as we've used to hear; we are somewhere in the middle with an expanded or blurred stereo effect. I wish I could afford two of them to try this, but I'm not one of those lucky people.

Shiral