A: One commonly accepted method for EQing monitors is to “ring them out.” Here’s the procedure: Set the gains on all of the mics to be open in the monitors to the same relative level, and then turn the monitor system up until feedback occurs. At that point, pull down the offending frequency on your graphic equalizer. When the feedback at that frequency stops, turn the monitor system volume up again, repeating the procedure. If you do this five to seven times, or until multiple frequencies (more than three) are feeding back at the same time (whichever comes first) then you have EQed your system for maximum gain before feedback. It may not sound great, but it will get loud!
Once you’ve accomplished this, you can turn the monitor volume down to a more reasonable level, and begin to tweak the EQ for better sound and to address other specific concerns — ringing the monitors out just establishes a good starting point. You’ll be surprised at how expert you can get at this procedure. Many experienced sound engineers immediately recognize the frequency of feedback, and can very quickly locate the correct slider on their EQ. As with most skills, practice makes perfect!
Disclaimer: Be careful when working with a monitor system in this way! feedback can fry components (including ears) if you’re not careful — keep your hand on the volume control! Ringing out monitors is not for the faint of heart, but it works.