I imagine the scale and power of the MCM stack would be impressive (and I don't just mean the footprint), to say the least, but I haven't heard them. But I have studied the available documentation about them, though.

Stacked in a pair, the throat size is correct for the "official" 30Hz in 1/2 space according to the Gillum patent document if I remember correctly. I would expect to be impressed, at any rate.

I have played around with a 2" tractrix midrange horn (DIY), and they have a distinctive "flavor", quite addicting actually. It has to do with the way that the sound propogates, rather than having a particular "sound" in its response. It's rather like when a nice speaker system broadcasts into a large, quiet, non-reflecting space. Except it's in your room. A positive effect, to say the least.

DM