In many smaller club settings your main sound system can face competition from the signals generated by the backline – the drums and amplifiers onstage. These project into the audience and can cause timing-related problems that are perceived as “smeared” audio. There’s a relatively simple way to combat this and produce a cleaner, more pleasing FOH sound.
First, we’ll note that pro sound contractors use sophisticated room analysis software to calculate the correct alignment times necessary for their FOH systems to sound their best. This function is built into the dbx DriveRack 260 and DriveRack PA, for example. Here’s a much less scientific – and more approximate – method.
Since the idea is to counter the sound coming off the stage, start by selecting the loudest acoustic source onstage. This is usually the snare drum. Have your drummer play single strokes on the drum, about one per second. Make sure he or she plays at “gig” level!
Start with the approximate formula that 1 foot equals 1 millisecond (rounding the speed of sound down to 1000 feet per second). Measure the distance from the snare to the drivers of your sound system and set the delay that’s connected to your FOH system accordingly. BE SURE your sound system volume is as close to equal the acoustic snare’s volume as possible. This won’t be your gig level; it’s just for purposes of setting the delay.
Now use your ears and add or subtract delay amounts until you hear the closest possible attack consonance between the stage sound and the speaker sound. You’ll get better at this with practice.