I saw them at a Superbowl of Rock show at Soldiers Field in Chicago about that same time. That was my first experience seeing the legendary (well, here anyway) "Magic Smoke". We were all assembling on the football field in the stadium while they were running pink noise tests. About 15 minutes into the testing a group of about 4 of those bass cabs let it all out. We, at first, thought it was part of the effects of the show, but no.
The show was quite impressive, as we were located pretty much right in the center of the field. The moving sounds were amazing. They had stacks setup in the stands all around the upper seating rows of the stadium.
My question is, how did they keep it all in sync as we were many hundreds of feet away from any of the deployments? I don't recall it ever sounding "off-delay" or echoey.
-Dennis