I'm not sure. It's either as other said, all the side channels playing at same time on sides, and/or matrix'd rears in a 6.1 track. Or, it could be some matrix of fronts spread to sides, but doubt it. I'd have to look into it, and any differences in IMAX vs. standard. My presumption is that the Steuspeed's position is mostly right. However, in the IMAX that I've been to, all the channels where "active" full range channels, with separate LFE, I believe. Could have been crossed over to 80hz from all channels, but not sure. Lol! I guess it could be anything really. I'm just presuming.
Yep, I will look into it, cause I want to know myself.
Perhaps with a few calls and some footwork, someone here can get to the bottom of the matter, and know exactly what's being steered where and processed how in these systems. I'm out of the loop myself, presently.