Those Quads are probably dipolar, which could explain the difference. I know that with omnipolars you can get some sounds walking on the ceiling above you. Front-firings are pretty consistent in the effect (when properly placed). I didn't experience any 3D effect when listening with headphones. Which made me draw the conclusion that it works through room reflections.
Here's another recording from my audition tool-set. Very well engineered, absolutely clean sound, pretty perfect. The first track, apart from being an auditive delight, will also let you know how deep in the low frequencies your system is going. Just make sure you don't play it very loud in a boomy room, if you get stationary waves it could be nauseating.
