At the Austin city limits festival a couple of years ago they staggered maybe a dozen stages around the perimeter of a park and played shows at the same time only on stages that were across the park from one another and not directly facing each other. Some were big stages and some were very small (the acts were everything from Wilco and Robert Earl Keen down to local talent). They also, as I said, didn't seem to be turning up the volume to brain-melting levels. Facing the stages outward (which sounds like a good idea) wasn't really an option because of the location/shape of the park (amoeba-shaped and surrounded by busy streets) but this seemed to be a reasonable second solution.