There seems to be an unexplained fear, or at least a hesitance, on the part of many musicians when it comes to getting their hands dirty on the middle part of a mixer. I’m talking about the EQ or Equalization (or what many just call “I need more highs”) section. While it does take a good ear and some commons sense knowledge, it is far from being rocket science.

Before we go any further and get into what does what lets get one thing straight: the most important skill you can develop when it comes to running sound at any level—from a small rehearsal room to a club to an arena—is learning how to listen. With all of the new high-tech toys now available, I frequently come across sound guys (and gals) who spend more time looking at laptops, touch screens and processor menus than they do actually listening to the band. They are, in effect, trying to mix with their eyes. This doesn’t work real well. When it comes to the smaller, transportable sound systems most musicians (as well as DJs) use its important that you not get too tied up in where the knobs are pointing. Listening is by far more valuable than making sure some frequency band is knocked up or down by 6 dB because some article you read said it should be. very system is different and you have to listen to get the most out of it.

A typical, quality, audio mixer will have anywhere from two to four bands of EQ on each input channel. Two is easy—one is high and the other is low. Kind of like the bass and treble controls on your home stereo. As we add bands, we get into the midrange and that is where things can start to get confusing.

Let’s talk about the various types of EQ. First, you need to now if you are looking at a true cut and boost filter or a simple roll off. With a roll off, all of the frequency content of a band is present when the control is dialed all the way on. Dialing it back “rolls off” the content of that frequency band. A true cut and boost is at zero or “flat” when the knob is at 12 o’clock (there is often a notch in the knob’s rotation at that point called a “détente”). Dialing the knob up or down either boosts or cuts the content of that frequency band.

Both of these types of EQs are centered at a specific frequency and have a “width” (which is how many adjacent frequencies they also affect) that, (for whatever reason) is called the “Q.” These frequency centers and filter widths are a huge part of what makes one mixer sound different from another.

The other type of EQ or filter is called a parametric or semi-parametric. These are also referred to as “sweepable” and are usually found in the midrange. A good mixer (IMHO will have four bands of EQ including two sweepable mids. A parametric EQ consists of three adjustments: first is the center frequency, next is the amount of boost and/or cut applied to the band and finally, the Q control which adjusts how wide the band actually is. An EQ that includes all three of these controls is referred to as true or full parametric. Most of the sweepable controls you will find on MI mixers will leave out the Q control (the width of the filter is fixed) and are properly referred to as “semi-parametric.)
The first thing I do with any mixing board when setting up is to “zero it out.” That means returning all of the channel faders, auxes and EQ controls to their zero setting. Remember, on a true cut and boost EQ, that “zero” setting is usually at the 12 o’clock position. As you gain experience and get a feel for your system, mics and players, you will find yourself making the same cuts pretty much all of the time (Like cutting at 120 Hz to take the mud out of a kick drum or cutting 1.25 kHz from a vocal mic.) When you get to that point, it is tempting to just make those adjustments automatically before really listening to the system—which is a bad habit to get into. Start flat and listen before you start adjusting.

When it comes to EQ it is ALWAYS better to cut than it is to boost. To use an anology from plumbing, assuming your main pipe is pretty full of water to start with (as it should be if your channel trim is set correctly) then adding EQ is like forcing more water into that pipe—which could overload it. In the audio world that means distortion and maybe feedback. When in doubt: cut, don’t boost.

So how do you get more bass, for example? Try cutting everything except the lows and then boosting the overall signal a little bit to get the same effect as just boosting the bass.

Originally posted 2008-11-17 02:16:28.