well, if you want it to sound good, then you probably need all the frequencies...

if you want a monitor mix that will help with feedback, you'll need to do each monitor separately.

in shitty rooms, i generally start with my seagull shaped EQ. cut a lot of the super-low (below 100) and super-high (above 10k) frequencies.

also dip some of the midrange feedback-proned frequencies ... 630-2k or so.

then the listener gets the lower fundamentals and the higher overtones. it's basically the bare minimum necessary. good luck

I must be lucky. Except for pulling down the low end "garbage" (below 80Hz), I leave my monitor EQs alone. How you EQ the system depends totally on the mics, the monitors, how they're placed in relationship to each other, and the acoustic environment the system is in.
With stage monitors, I seldom worry about the "body" of the sound. That range (200-400 Hz) is going to "howl" if you emphasize it. And it's going to "muddy up" the sound on stage with resonances and standing waves you really don't want. Many times pulling that range down a bit will help the vocals come across better onstage without increasing their gain. Try not to listen to the musicians onstage that tell you they want more "body" or "balls" on their voice during the soundcheck. Trying to satisfy them that way will simply make matters worse when they start playing. A little bit of "thinness" (I don't mean "tinny") will go a long way when they start crankin' up and need to hear themselves.
The "presence" range (3K+) will give you more "cutting power" but boosting that can induce shrieking, especially if the mics are designed to emphasize that range to begin with. So I usually choose mics (Shure SM57/58, Sennheiser 935s) that tend to gradually boost the highs in that range so that I don't have to EQ it in. The less you have to do at the equalizer, the better, mainly to maintain system headroom and to minimize phase shifting artifacts.

*light bulb* ahhh.. thank you all for your input :)

question, if the environment is open air, what adjustments are there or any extra considerations I should be looking out for.

Rain. :D

Never done an open air concert, always been small(ish) halls and once, a real high church.
However, you won't need to worry about room echoes if it's open air.

lytes wrote: *light bulb* ahhh.. thank you all for your input :)

question, if the environment is open air, what adjustments are there or any extra considerations I should be looking out for.

There are no set frequencies that anyone of us can tell you to boost or cut or reproduce. That is silly.

It is all dependent upon what gear you have, your band/artists, whether they wear hats or not, whether there is high humidty or low, hot or cold temperatures, etc, etc. It can even be as simple as one microphone cable or an excessively long snake run failing to reproduce high frequencies. Too many variables.

You should read the Yamaha Sound Reinforcement Handbook. It has some good basics. The best way to use monitors is to fill in the difference between the band mixing themselves on stage, and the mains. People tend to mix monitors first, want full bandwidth audio (which is insane) without trying to play with the mains only first. The mains are going to have 360 degress of mids and bass, especially mids if they are line arrays, and most people in the entry level don't think of that. So monitors do not have to be very big, or beefy sounding. Most generally, you only need 100Hz to 15kHz, where the human vocal range is. Anything else is cake.

lytes wrote: question, if the environment is open air, what adjustments are there or any extra considerations I should be looking out for.

these are the best!!

outdoor / open air stages are my favorite because there's no sound bouncing around from ceilings and walls!

it makes mic gaining and monitor mixing way easy. however it usually requires more powerful amps/speakers because a lot of sound gets "lost" to the open air.

but i always get the best sound in a predictable environment like the outdoors!