Having stood in front of him last new years... they're all hooked up. It's not that its really loud, just that its really... there. He moves a lot of air with those speakers and it creates some great bass tone. I have to say that the tone he hears from those cabs is a little bit meatier than the tone that we hear on a board tape. Just a product of mixing I suppose. My guess is that there is so much bass rumbling around the room from his actual rig that they don't need all those sub frequencies in the main mix... but I digress. They're all on and they're all loud and proud sounding.
Viola Lee Blues "chord of doom" ? BUHM!!!!!!! It makes your innards rattle.