Another important reason for horn loading (especially in mid top use) is to control dispersion. The old days (1970's) of 50 horn mid and top boxes shooting in all directions is over. Proper control of dispersion has many benefits. The effects of lobing and comb filtering can be radically brought under control and, the sound can be directed where it is needed, at the audience, not at the walls of a venue where reflections will end up energising the room and making for a less intelligible sound.The fact that only the audience is targeted means you need less power than a system that scatters everywhere. A football field stadium with an audience of up to 70,000 people expecting up to 125 dB in most positions can be had from an all horn loaded system using around 40,000 watts. I have worked and mixed on non horn loaded systems in these same venues with systems of over 150,000 watts and not got as high an SPL at distance, and a far less intelligible sound. The 150 Kw system with all its amps takes three 32-ton trucks, 18 crew and 2 days to assemble. The 40 Kw system will fit in one 32-ton truck, needs only 6 crew and an afternoon to setup. Need I say more.
Best wishes,
Rog.