by Nathan Smith
It’s Sunday morning, you’re in the middle of your worship set. Everything is going so well, and then…a loud squeal shoots through your speakers. Everyone has a deer in headlights look on there faces and they all turn to stare at one person. Who is that person you ask? Yes, the under valued and usually under trained sound tech.
The thing about sound, is no one pays any attention to the sound teams when everything is going well. It’s only when something goes wrong that the sound tech is noticed. While there is much to say about including you sound techs in your normal worship team fellowships, pre-service prayer times, and such, this will focus more on preventing problems before they emerge.
ON THE EDGE OF FEEDBACK
There are many ways to troubleshoot a mic that is about to feedback (BEFORE it’s too late). Simple put, you need to find the frequency that is causing the problem. The easiest way to find and destroy unwanted frequencies is by using a parametric EQ. Most boards have them, at least one anyway. A basic board will have a low, high, and a parametric mid EQ. The parametric mid EQ allows you to “sweep” through a range of frequencies (like 250hz to 1000hz) and then has a second knob to control the decibels of that frequency.
For example: Say you have an acoustic guitar that has a mic inside of it. You are sending the signal into your board and back to the stage through a monitor. If the guitar is turned up too loud in the monitor the sound coming from the monitor will bleed into the mic inside of the guitar. The will start to create a feedback loop. Usually starts with a low hum, and steadily grows until the guitar and the whole stage is vibrating with this loud mid range hum. If you could locate that specific frequency (like 300hz for example) and turn ONLY that frequency down you would eliminate the problem. You would have to turn the whole guitar down to prevent the feedback, you would only need to turn down that one frequency.
Use this technique on all mics that are causing issues. Especially lavaliere mics for your pastors and speakers. Use the parametric EQ to sweep through the frequency spectrum until the frequency on the edge of feeding back is located and turned down (using the decibel know paired with the EQ knob).
February 25, 2014