First best option is to set your
console up in the theater. Preferably a digital
console with
stage boxes in the booth to
pick up your analog inputs and a data cable punched through a cable pass-thru in your wall to drag the necessary data,
power, and intercom cables out to your mix position in the theater where you would probably have to remove 3-4 seats to make room for a small table and the
console.
It's not ideal to mix from a booth but it can be done if you have a pair of
monitor speakers.
Trick is you don't want to EQ them
flat. When you output L/R to them from your mix
console, you want the output EQ's driving your monitors to reflect how the main
system in your theater sounds. If your room has a 2K notch to avoid some awful
feedback, you want to reflect that in the EQ on your booth monitors.
To be
clear, I'm not saying you should EQ your booth speakers with the same EQ settings as your mains. That 800Hz boost on your
system EQ may serve a very specific purpose to your main speakers that doesn't apply to your booth monitors. What I'm saying is if you listen to a music
track on your mains, then walk into the booth,
mute your mains and listen only through your booth monitors, it should sound approximately the same as when you were in the
house but maybe a little quieter.
You also want to delay your booth monitors to time align them to your mains. Not a big deal when you have the window closed, but when you have the window open you definitely want the booth monitors to behave as an extension of your main
system, time aligned to your mains, and with a proportional
level to your main speakers.
For your less-experience techs, I would also put a chart near your
console in the booth that gives a sense of purpose to your output
LED meters. This way if your booth monitors are turned down and the window is closed, someone can look over at the output meters and get a sense of just how loud it is in the theater.
An example, with numbers I've pulled out of thin air:
-12dB Uncomfortably loud
-15dB Good
level for music, or speech on top of music
-18dB Good
level for speech by itself
-21dB Really quiet
As for a pair of decent booth monitors, I'm a fan of the Klipsch R-15PM's, which will run you about $350 new for a pair. They sound great out of the box, but that doesn't matter. You're going to chop their EQ up in your
console to make them sound just as great or as terrible as your mains.
Desperate times, desperate measures, you can repeat this same process by putting a pair of quality
headphones on your sound op. However, what you hear from a pair of
headphones is unusually clean -- you don't hear any of the left signal in your right ear and vise versa. This gives a false sense of pure stereo that no main PA
system in the world can offer and should not be used for trying to craft some kind of stereo mix nobody in your theater can discern from your effectively
mono PA
system.