“You know, I’ve been doing sound here at my church for about two years now, and there are a couple of things that aren’t quite clear to me. First, where’s the bass and treble control?
And, what are these knobs for - the ones on the console labeled high, mid and low?”
Believe it or not, I’ve heard questions like this posed more than once by people who do sound at their churches. It’s these folks, and others afraid to ask about things like the EQ section on the console, to whom this article is devoted.
First let’s take a look at the audio console EQ section. The picture below (click to enlarge) is an example of a rather basic EQ section on a Mackie 3204 console, a common board in many churches.
As you can see there are four separate knobs, one each for high frequencies, mid-range frequencies, and low frequencies, and one to select the center frequency for the mid control.
To equate that to the stereo at home the High frequencies would be those controlled by your treble control, which also overlaps into the mid-range frequencies.
The bass control at home would be similar to the low frequency control on the console.
That fourth knob, the one for determining the frequency for the mid-range filter is what confuses many people. Let me take a shot at clearing up the confusion.
First let’s review just what happens when we turn any of the control knobs. If we turn the high, mid, or low knob to the left we will begin to turn down those frequencies.
Most high frequency controls such as this one are centered around 12,000 hertz (or “12 kHz”). That frequency is, for you musicians, about F# in the ninth octave on the piano. Or in layman’s terms, really high.
What we control up at those frequencies would be mostly to add crispness to an instrument or to take the “S” sounds out of the speaking or singing voice. The control though centered at 12 kHz will effect on most consoles, about two octaves of frequencies.
The same is true of the low frequency control.
It is usually centered around 80 Hz and is used to enhance bass vocals, and low frequency instruments.
Also, because low frequencies tend to go everywhere and often cause feedback, we can use this control to cut that frequency back in some inputs.