I used to work in a 2500 seat theater that had 3 clusters almost identical to this. Left, Center, and Right. Originally they would have powered the horns with a 50 watt Altec mono amp and probably used autoformers to attenuate the horns for coverage. The bass bin would have been powered by a 200 watt mono amp. Altec 1593B and 1590C respectively. The 1593B had a switchable 800hz highpass filter right in the amp.
That same theater had a Technics 1200 turntable hooked up to the console when I started there (early 2000) and I would put on some Steely Dan or Pink Floyd on and listen. It was quite the time machine....
I think they have all been replaced now, but as late as 2008 they were still using the Altecs as mains, although the whole front end was rebuilt. We used Crown K1's to run everything, with BSS processing. It still sounded quite good, but you could tell the magnets were worn out. Each cluster sounded quite different from each other.
