Fine Tuning Your EQ – Joe Bigham
We often see many musicians who have eagerly entered the world of acoustic amplification. They have purchased a guitar with a pickup built in, new preamp, or new amplifier and are ready to crank out the decibels. Yet, they can often be confused by the new set of controls they must contend with to get a good sound. In this article, we shall examine the different types of EQ options, and how to easily find the sound you are looking for.
Shelving EQ and Sweepable Mids
First, we need to discuss three different styles of EQ controls. Most Bass and Treble controls fall under the heading of shelving EQ, meaning that they cut or boost from X frequency and everything above it (for treble controls) or everything below it (for bass controls). Therefor , if you find your tone a little muddy, a reduction of bass will clean up the tone but may also reduce some of the low end punch. Conversely, if you find the trebles too dark, a boost of the treble will brighten up the tone but will also bring up the volume of hiss.
So how do we adjust just one frequency? We use the sweepable mids control to find the frequency we need. Many times, this control actually comprises of two knobs, one for cutting or boosting and the other for choosing the frequency. On guitars with onboard preamps, these two controls may also be labeled mids and contour. A boost in the lower mids will fatten up a sound, while a cut will eliminate any muddiness. A boost in the upper trebles will allow the instrument to cut through the mix better, while a reduction will reduce any harshness in the tone.
The last style of EQ which is not nearly as common is the standard graphic EQ, in which each slider adjusts one particular frequency. Graphics can be very useful where multiple points of adjustment are required. Still one must beware not to cut or boost too much as each slider affects not only its designated frequency but many of the surrounding frequencies. Each slider produces a bell shaped curve in the EQ with the peak of the bell at the designated frequency. As an example, if you are boosting 500 Hz on your graphic EQ, some of the frequencies up to kHz will be affected as well.
So how can you begin to find the sound you want. First, set all of the controls flat, typically being in the center position (unlike electric guitar amps in which all controls are typically cut only) and turn the volume up to roughly your expected stage volume. Second, boost the mids control until you can hear the frequency knob taking effect. Sweep through the frequencies and you will hear which add to your sound and which frequencies sound bad. If you have only one mids control, it is better to reduce the offensive frequencies rather than extremely boost any others that may just sweeten the tone. You may also find some frequencies that easily feedback; use the mids control to cut these frequencies. Adjust the trebles and the bass to taste, again being careful not to boost what you may have already cut, or vice versa. Remember that most of the knobs allow for 12-18db of change, which is quite extreme. You will probably only need to boost or cut 3 dbs in general. Any more than that will begin to sound unnatural and may cause feedback issues.
One final consideration is to consider the context of the instrument. In a band situation, many other instruments compete for the same sonic space. By using the EQ, you can find your own space unobstructed by other instruments. A tone with no mids will be hard to hear in a group setting, while one with too much mids will make the mix to crowded. By slowly listening to the effects of each EQ adjustment, you will get a much better idea of attaining the tone you desire.