Oh, do tell, please
"Back in the day" (on that tour) they were using the ServoDrive subs.
Tom Danley was invited out as a guest.
At one point in the show, the band was not playing-the audience was quiet and Bono was talking to the crowd.
Tom said he could barely make out (understand) what was being said.
At that point, he started moving his focus from subs to full range cabinets-saying to himself "There MUST be a better way to make it sound clearer".
So his quest began-first with getting an understanding of what would be causing the problem-then looking for a different way to do it/fix it. And with lots of various previous products and the knowledge gained from them-after a few company and owner changes, he hooked up with Mike (who I already worked for) and here we are