Tuning a PA system may appear to be a daunting task, but it does not have to be.
There are complex scientific methods for doing this that involve unpleasant-sounding “pink noise” and expensive computer software, but you can do the same thing with just some recorded music, a graphic equaliser, and your ears.
If you are unfamiliar with the setup of a PA system in general, you may want to read How to Set Up A Sound Board before reading this article.
Note: The terms “Equalizer” and “EQ” are used interchangeably in this article.
1. Set up and test your public address system. This includes your graphic equaliser (s). Make sure your EQ’s inputs are connected to your mixing desk’s left and right outputs, and that the equalizer’s outputs are connected to your main left and right power amps.
2. Make sure that both the graphic EQ and the EQ on the mixing board are set ‘flat’. That is neither boosting or attenuating any frequencies.
3. Play some music by connecting your playback device. It is best to play a song that is A. familiar to you because you need to know how the track should sound, and B. similar in style and instrumentation to the music you will be mixing with the PA system.
4. Listen. Take a walk around the room while the music is playing and notice how it differs from how it sounds when you listen to it through headphones or on your home stereo (this is why you need a familiar piece of music). Your goal is to eliminate or reduce these differences as much as possible so that what is coming from your CD player is reproduced as accurately as possible by the PA system.
5. Make changes to your graphic equaliser. Begin at the low end of the equaliser and gradually increase each frequency, one at a time, while your music is playing.
As you increase the frequency range, listen to how the sound changes. If increasing the amount of a particular frequency makes the music sound worse, reduce the amount of that frequency until the music sounds deficient in that frequency range. If increasing the amount of a specific frequency improves the sound of the music, leave it flat (neither boosted nor attenuated) for the time being.
When boosting high-midrange and high-end frequencies, use caution because they can be piercing if boosted too loudly (it is not necessary to boost any frequency all the way up, just up enough that you can hear the difference).
6. Rewind and listen again. After you’ve gone through each band on the graphic equaliser, go around the room again (with the music still playing). Again, you’re paying attention to how the music differs from what it sounds like through headphones or another familiar playback system.
7. Compare without the EQ. On your graphic equaliser, press the “Bypass” button (or toggle switch). Consider the difference between the EQed and bypassed sounds. This will show you exactly what you have changed with the graphic EQ and whether some of your attenuation is too extreme or insufficient.
You might want to take a walk around the room while someone else uses the Bypass control.
8. Make any necessary adjustments until the sound is satisfactory. Essentially, this article could be summarised as “play with the graphic equaliser until it sounds good.” It appears to be very simple, and it is. It may take some time to get the hang of it, but the more you practise, the better you will become.
The fancy computer software for PA tuning does nothing more than send noise through the system, the frequencies and proportions of which are already known, and then analyse the sound that comes back and measures the difference between the sound it sends out and the sound that comes back. This is basically what we’re doing here, except a little less precise and with a little more leeway for personal preference.
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