I haven't had my Sphere apart, so I can't tell you what's inside,....actually I'm not really sure how to get it apart.
Yeah, with regard to incoherent, binaural mics are really meant for the headphone experience. This is because all the reflections from the ears to the bridge of the nose are already recorded in the signal (head related transfer function, or HRTF)...when you play back on speaker you get this HRTF again. Sort of like filtering the signal twice...
Cheers,
Kris
PS: I did a little digging, and if you can find the following references you may get an idea of what's going on inside the sphere:
Theile, G.: On the naturalness of two-channel stereo sound.
J. Audio Eng. Soc.(39), 1991, pp. 761-767.
Horbach, U:: New techniques for the production of multichannel sound.
103rd AES Convention, 1997, Preprint 4624
Basically, Theile is the guy you want to look for...