EQ, or equalisation, to give it its full name, is the tool we use most in music production. It’s a frequency modifying processor that changes the tone of whatever you’re processing, and if you’ve ever used bass and treble controls before, these are a simple form of EQ. The other similar and related concept you’ll encounter is a filter, and this also influences the frequencies you hear. For convenience, we generally say that an EQ can both cut and boost the selected frequencies, whereas a filter only removes selected frequencies. That said, you will encounter some EQs that only cut or boost, and you will also find that resonance within filter designs actually results in frequency boosts, so things aren’t quite that simple.
The EQ you have in your DAW is a powerful tool and will typically include a number of bands, each with a boost/cut control, frequency control and sometimes a width (Q) control. If it has all three options it’s called parametric. Even so, not all EQs are the same and this is to do with various shapes or filter types they employ. The most common shapes are low shelving, high shelving and peak. For the shelving design the frequencies above (high shelving) and below (low shelving) your designated frequency are affected when you cut or boost. Meanwhile for the peak shape, the boost or cut is centred around the designated frequency. The Q setting, if included, will influence how steep a shelving design is and how wide or narrow (bandwidth) a peaking design is. In addition to these three shapes, you’ll also find high-cut (low pass) and low-cut (high-pass) filters. These filters remove the frequencies above or below, respectively, a set cutoff frequency and that frequency is usually adjustable. They often have an adjustable slope, which affects how aggressively they remove said frequencies. They may also have aQ setting and this controls resonance at the frequency cutoff. As mentioned, higher resonance settings can create a boost at this point.
“You can change the tone of your sounds with both EQ and its related filter”
That’s the basics, but EQ plugins come in many different designs. Some are analogue emulations, which may mean more limited controls or specific filter shapes and behaviours. Additionally, many EQ plugins are now display-based graphical EQs that are highly flexible. Other designs you might encounter include graphic EQ and this has many fixed frequency bands spread across the frequency spectrum, each with cut and boost. You might also encounter linear phase designs, and these maintain phase coherency, avoiding the often desirable phase shifts that a typical analogue design introduces.
Filters, meanwhile, can be equally varied, and you’ll find certain shapes can impart quite distinctive tones and textures including voicelike tones to sound. It’s this particular aspect that we investigate with our third walkthrough.
The instruments
Our three EQ plugins are OverTone DSP AF2-10 CM, DDMF IIEQ CM and AudioThing The Orb CM.
OverTone DSP AF2-10 CM is a slimmed down version of Overtone DSP’s AF2-10/M plugin. It’s a display-based EQ that models the shape of analogue filters, so it not only sounds great but is immensely easy to use. With up to four bands, +/-18dB of gain and a flexible choice of filter shapes and behaviours, this is also a pretty powerful EQ.
IIEQ Pro CM from DDMF is also a compact graphical EQ. With up to six bands, +/-20dB of gain and series or parallel band configurations, it’s more powerful than its simple interface would imply. What we really love though are the 19 filter shapes, including the handy notch shape and less commonplace band/shelf design.