I don't know if you will read this Jim, but Zanash is referring to the classic wave propagation/reflection experiment that involves making ripples on water and looking at how they are reflected.

Planar speakers are not entirely free of a baffle though, as you suggest. At best they have a vestigial baffle - very few speakers have no support frame to hold the drive units in place (MBL perhaps and a couple of others). Planar speakers still produce horizontal dispersion and any edge will cause secondary diffraction to occur (dipole operation doesn't stop this).