I have a photo of the system (minus the horns on the bottom) in the shop bathroom-along with an airplane shot of the crowd.
The delay towers were 1000' back and the crowd went well beyond the delay towers. I would suspect something in the neighborhood of 3000' back.
I wonder what people actually heard.
I went to a 4th of july concert at the Washington mall back in the early 80s to hear the Beach boys.
I could barely see the stage. My wife and I sat down eat lunch while the "background" music was playing. I could tell it was music of some sort-but could not hear or understand anything. I found out later that while we were sitting there-3 dog nigh and Ringo star had been playing.
Then the beach boys came on. The only way I could tell it was them was that a local radio station was broadcasting it live-and all the drunks around us started singing to the radios they had.
We got up and left-there was no way I was going to sit int he hot sun and listen to drunks sing Beach Boy songs------------------
I never heard them through the PA.