No, we are not talking about that truck driver that recently drove a rig into Lake Ontario. Rather we are outlining the procedure for ensuring that your stage monitors and microphone have their frequency peaks removed and that their resonance is not acoustically coupled to the stage environment. This includes, but is not exclusive to, walls, ceilings, stage and riser resonance. In other words, anything that can set up a sympathetic vibration with frequencies emitted by the stage monitor. Equalizing out these frequencies is the answer. Unfortunately, the more analog equalization that is used, the more phase shifts you create. It is best to strike a balance that will address the worst resonant rings while not varying the EQ curve wildly. The procedure goes like this:
- Zero the EQ on the console rails and the graphic EQs for each monitor mix.
- Have the microphone and monitor placed correctly on the stage.
- Turn that channel’s monitor send until you hear the first resonant ring just before feedback.
- Find that frequency by nudging the graphic EQ bands up and down quickly and cut it as many dB as necessary to improve the feedback threshold.
- Turn up the monitor send further until the next ring is heard – find that frequency. Cut the resonant frequency down accordingly.
Continue in this manner until you have all the monitor volume the band could require. For a maximum setting, keep going until you hear multiple simultaneous rings or when one or more of the graphic EQ sliders that could correct the present feedback is at maximum cut. If all goes well, you will be able to operate the stage monitor at least 6 dB below the resonant ring point and have compliments from the band at the end of the show.
Richard van Steenburgh and Ted Barker are from ShowPro, a sound system rental company in Toronto, ON.