i don't want to start a flame war or something...
but: i love how everybody is talking like he would be a live sound engineer....
seriously, live and studio are two very different things... often bad sound is caused by people who think they could do better as they are a good in the studio and convince other people (a band or management) that they could do better then the last (and maybe very experienced) live sound guy they've had.
in live sound you have to deal with some things that you'll never have in the studio, home studio or where ever where you have total control over everything going on in the mix.
1. The actual room, room size and shape. live rooms sometimes have reverbs of about 3 seconds!!! imagin sound checking a snare drum in an empty room with 3 sec reverb on it... as well as comb filter effects while sound checking and room resonant frequencies due to size & shape. the key to handle that kind of room is volume. but in a scene where "loud=better" it is a kind of hard to make people (band people & management) understand.
2. The PA. Studio monitors are mostly phase correct even when working with a sub speaker (phase not polarity, yes: phase is not polarity). Understanding how big speakers work and why they do as they do is helpful.
3. Stage volume & phase issues due to time differences, interference caused by stage volume. if you have 8 different sources streaming the same signal at 120 db/flat it is supposed to be muddy. guitar amps for instance. the guitar player is super loud out of his cab on stage which points directly at the foh guy. he wants to have his guitar in his wedge, drummers wedge, second guitar players wedge, PA and, as he has a big ego going on, in the side fills too. that makes it 8 sources (cab, mon1, mon3, drfill, sideL&R, PA L&R). pointing in different directions & hitting the audience with different times. this actually is like putting 8 different mics in different spots of a room and hoping for a nice direct and transparent sound... not working at all...
4. phase and time alignment in a PA it self. sometimes bad measured or bad placed pa systems (yes 5 centimeters can make a big difference in this case) can cancel out crossover frequencies. this could mean no signal at 120hz, 1k, 5k at all. i guess most of you would not even know how to get those back even if an analyzer is clearly showing that those frequencies are missing. boosting the frequencies is not working btw...
5. feedback and phasing issues due to stage monitor volume and/or multiple mics and bleed from different instruments (in maybe lead vocal mic).
6. last but not least the so often mentioned sub-thing. most PAs are configured to have a low shelf with something around +10 db starting at 80hz having full power at 63hz down to 30, sometimes even lower. i guess most of you will end up in having trouble with to much sub in the mix
these are just a couple of things you have to deal with, sometimes even the "different gear every night" can cause trouble. yes i have made bad mixes too. but i think i can say: i did my home work and these days my mix quality is very good and steady in a tour.
but when it comes to live sound, all i can really say is, the more control i have, the better i can work, the better the mix will be. if a band has around 104 db/a at foh in a club just with backline and monitors, they give me around 1 db/a to put vocals in and bassdrum, because that is the only thing you can not hear without the system
on big systems usually the band can be pretty loud on stage without causing problems but as the sound guy you might have to deal with different stuff that is maybe very challenging. like silent sound check with a change over of 20 min with 40 inputs to check and 15000 ppl waiting for your band.
and last thing, yes there are a lot crappy sound guys out there, i just wanted to let you know that live sound is different
