Re: Compression
It's important to remember that the sound coming off the stage doesn't travel in one narrow, straight line from the snare drum, past one speaker, and toward one listening position.
While delaying the sound system to match the backline does make sense at first glance (and often does, I agree), you can get weird effects. Examples:
In a shallow, wide room with PA either side of the stage, a lot of people may be further away from the speakers than from the backline. Delaying the mains will just make the offset worse.
Another one would be where people in the audience are up close to a stage and hearing monitors and PA at the same time. Since you can't delay the monitors anyway, you might as well leave the mains alone.
Yet another one is where there are center clustered subs. People in the middle would benefit from delayed subs, while people one the sides would benefit from delayed mains...all the while the people on stage probably would not like delayed subs much at all.
