In the sound reinforcement industry, flown subs is a relatively new trend. In the early days of large scale sound reinforcement even the main PA was typically stacked on the ground, stage or located on scaffolding to raise it up.
What is the benefit of flying subs?
For one when they’re on the ground those closest to them are getting a lot of low end. For instance, those standing right up against the barricade. If you’re 3 feet away from a sub array, it’s going to be really loud in comparison to those who are 30 feet away or 300 feet away. By flying your subs you equalize the distance at which the audience can be in proximity to your subs. Another benefit is that when your subs are flown with your mains you have the opportunity to time align the subs for a larger portion of the audience. When you fly your main speakers and put your subs on the ground, you’ve got a limited amount of time alignment choices and none of them are going to work for the entire audience.