PA System article
Common Pa System Mistakes to Avoid
Most live sound problems come down to a short list of repeatable errors. This guide covers the six most common PA system mistakes and how to avoid each one before they happen.
Live sound problems are almost always caused by the same errors — and most of them happen before the first song starts. These are the most common mistakes made when operating a PA system, along with how to avoid each one.
Setting Gain Too High or Too Low
Incorrect gain is the root of most PA system problems. Too much gain and channels clip during loud moments; too little and the fader is maxed with no headroom. The correct procedure is to set gain while the performer plays at actual show volume, aiming for the channel meter to peak consistently in the green with occasional touches of yellow. Do this for every channel before the show. Redoing it in the middle of a set while trying to mix is far harder than getting it right during soundcheck.
Placing Speakers Behind the Microphones
Speaker placement is the most controllable factor in feedback prevention. If the main speakers are behind the microphone line — further from the audience and closer to the stage — every channel is working against itself. Main speakers should always be positioned in front of (audience-side of) the microphones. In small venues where this is difficult, angle the speakers outward toward the wings and ensure the monitors are not aimed back at the microphones. This single change prevents the majority of feedback problems.
Not Doing a Proper Soundcheck
A PA system that is set up without a soundcheck is a gamble. Soundcheck is where you identify which frequencies ring, balance the monitors, set gain for each channel, and identify any equipment problems before they become visible to the audience. A compressed soundcheck — fifteen minutes instead of an hour — is better than none, but it requires strict prioritisation: gain first, feedback management second, monitor mix third, house mix last. Never skip the soundcheck entirely, and never assume that because it worked at the last venue it will work the same way here.
Using Too Much Reverb
Reverb on vocals is the most overused effect in live sound. A small amount — one to two seconds of room or hall reverb — adds presence without destroying clarity. More than this, particularly in a reflective venue, makes the vocals unintelligible and the overall mix muddy. In a large reverberant room, use less reverb than in a dry acoustic space. If in doubt, listen to the room itself: a naturally reverberant room is already adding reverb to everything the audience hears.
Scooping the EQ
The "scooped" EQ — heavy bass and treble boost with the mids cut — sounds impressive in isolation but disappears in a mix and contributes to feedback. Mids (around 500Hz to 3kHz) are where vocals and most instruments live in terms of intelligibility. Cutting this frequency range makes the mix sound unnatural and hollow in a room full of people. Keep mids present, use the high-pass filter on every channel that doesn't need bass, and EQ to solve problems rather than to shape a preconceived sound.
Ignoring the Room
Every room is different. A PA system that sounded right at the rehearsal space may sound boomy, harsh, or thin in a different venue. The audience absorbs high frequencies; a full room sounds different from an empty one. Walk around the venue during soundcheck and listen from where the audience will be standing, not from behind the mixing desk. Adjust the main EQ to compensate for the room's specific problems — not to make the mix sound good in the sweet spot at front-of-house.
Where to Go Next
For a full introduction to running live sound, the PA system beginner's guide covers the whole process from setup to pack-down. For equipment decisions, the complete buyer's guide covers every component.
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