I've got Siege Train Horns on my car.
8 trumpets, 5/8" air lines, 8 gal tank, 200PSI, 148dB.
I don't know which system/compressor you have, but I would recommend changing the power wires from the battery to the relay and the relay to the compressor to at least 8 guage. I went for overkill and mine's 4 guage. The reason I say this is I have already burned out one compressor cause it wasn't getting the Amps nor Voltage it needed. I had a Viair 350C (235Watts) and have since upgraded to a Viair 480C and its 260Watts. Bottom line its not gonna be happy if the battery voltage drops below 13V.
After realizing this, I also put in a kill switch to a relay on the compressor power line so I can completely shut it down if I need to. I have also upgraded my alternator and done a BIG THREE wiring upgrade. I never let my compressor run when the engine is not running and I clean my tank once a month at least.
Tell me more about what horns, what compressor, and your air supply lines you have and I should be better able to assist you.