Sound is not as simple as plugging it together and turning it up. If it were anybody could do it. We have all heard bands with bad sound. almost all of the complaints about a band with crappy sound is that it's too loud.
Let's face it even if it's the best band in the world. if the band has crappy sound. The band sounds crappy.
You can achieve the 'Too Loud' problem even with a 100w PA and two little speakers. Loud has little to do with power and size. It has to do with frequencies and how the ear is sensitive to them.
Fletcher Munson have done some considerable research on this and have published an equal loudness countour that can help you to see average hearing sensitivity. This doesn't mean you need to set your EQ's to this curve, that's not what they're for. (more on that later). But as a sound guy you need to understand it and be aware of it constantly.
If the audience is complaining it's Too loud, and you just turn it down and then find the vocals are hard to hear or notice the stage is now driving the house, then you know it's not the overall volume that's too loud, it's just certain frequencies that are piercing or annoying everyone.
The louder you turn up the volume, the more you need to adjust your curves or balances to compensate. the 2k and 4k don't need the same power adjustments as the 200hz or the 630hz does. just because your running at 120db doesn't mean it has to sound loud. with the right care and well chosen boosts and cuts, 125db can sound great. it'll sound big, rich clear, warm, but not LOUD.
I'll come back to this later.
Girdwood Forest Fair @ midnight