Outdoor public address has no room to help it. There are no useful reflections, level falls away with distance, and wind and temperature bend the coverage you designed.
Distribute rather than concentrate
That argues for distributed systems: more loudspeakers, closer to listeners, each doing less work. A single high-powered cluster attempting to cover a whole ground will be too loud at the front and unintelligible at the back, and will carry furthest exactly where it is least wanted.
Weather protection is a specification
Weather protection is specification, not accessory. Enclosures, mounting hardware and cable entries all need to survive the site's worst season, and horn designs intended for permanent exposure behave differently to indoor cabinets pressed into service.
Plan for the neighbours
Finally, plan for the neighbours. Directivity that keeps energy on the audience and off the boundary is the difference between a system that stays commissioned and one that gets turned down permanently.
