Subtractive equalization is a technique used by most professional engineers to create clearer, more defined mixes. In order to have a clear mix where all instruments are heard, space will need to be made. Two sounds cannot occupy the same tone or frequency range and maintain clarity. If two sounds do occupy the same frequency range, the louder sound may mask, or hide, the quieter sound. Ultimately, mixing is about “crowd control.” Space must be created for a sound to be heard.
Many inexperienced engineers tend to add what they want to hear first. For instance, if the goal is a bigger, bassier kick drum, a novice may add more bass to the mix. A better solution is to take away from one of the other frequency areas that are dominating the sound, for example, reducing the amplitude around 600 Hz. The result will be more bass on the kick without adding destructive low-end. When mids or highs in the kick drum are cut, more bass will be present.
Also, the area that has just been cut opens up more space in the mix for other instruments to be heard. This is the subtraction in subtractive equalization. This doesn’t mean that frequencies should never be boosted. Start by subtracting first, and then add frequencies only as needed.
General EQ Areas
Frequency recognition is crucial to being successful in audio production. One of the easiest ways to become familiar with the different frequency ranges and the number that goes with them is to initially divide them up in the following manner: 100 Hz – makes things bigger, fatter (kick drum). 1 kHz – adds attack, makes the sound more “In Your Face” (snare drum). 10 kHz – makes a sound airy, breathy, or brighter (hi-hat or cymbals).
These are great EQ starting points. After you have taken out any unwanted frequencies (applied subtractive EQ’ing techniques), ask yourself, “Do I want the sound to be fatter, more up front, or brighter?” If the answer is “fatter,” start at 100 Hz and adjust from there. If the answer is “more up front” or “more aggressive,” boost 1 kHz. It may turn out that the correct equalization is another frequency like 2 kHz or 900 Hz. Whatever the adjustment, the key is in getting to the general area.
If the answer is brighter, breathier, or airy, try boosting 10 kHz. Ultimately, a different frequency may be boosted, but adding 10 kHz should get you started.With some generalization and through communication with the client, it will be much easier to recognize the frequency that needs to be adjusted. Locating and equalizing something quickly will hopefully keep a client happy and coming back for more!The following are seven common EQ points of interest: subs, big/fat, muddy, boxy/hollow, in your face!, presence/clarity, and airy. Becoming familiar with these seven areas can help you locate a specific EQ point quickly.
Following this section are even more terms to help you describe and communicate audio frequencies and sounds.