The “Q” part of an EQ
What does “Q” mean?
The “Q” on an equalizer determines how wide or narrow a bandpass filter will be. The number or dial setting on an EQ is built on an equation that represents the “Quality Factor.” The quality of the band comes from this equation–but here is a simple way to remember:
High Q = Narrow filter
Low Q = Wide filter
Does the Q vary between parametric, graphic, shelving, etc., types of EQ? Yes! Each type of EQ filter (bell, shelf, cut, etc.) modifies the quality factor equation. But it still employs the equation–it just adds onto it. If you look at a shelving filter or a low cut filter, half of it appears “normal” like we would expect.
When to use a broad vs. a narrow Q setting on your equalizer
Narrow Q (<1 on parametric EQs): Use to solve problems with masking or overlapping between tracks. A narrow Q is useful to target specific frequencies, so using it to reduce a frequency zone by 2-3dB will help to get a track out of the way from another. A small boost with a narrow Q can also be useful–it can add resonance to the track, which can help to emphasize the attack on a percussion element.
Broad Q (2-5 on parametric EQs): Use strategically to create a sense of separation between tracks (for example, you could perform a narrow cut on one track and a broad boost on another track). Broad boosts are helpful for emphasis, while a broad cut is useful for de-emphasis.
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The Q is a powerful feature of your EQ processing: it makes EQ a very flexible tool that can be used to reduce a wide band of frequencies, or to narrowly chisel out a specific frequency area. It can also help to highlight a very precise frequency zone or to emphasize a larger part of the sound.
Remember: sometimes cutting or boosting great amounts is not the solution to a problem, so start with a smaller amount of about 3dB. Make sure that the filter is centered on the frequency area that contains the problem. From there you can adjust to six, nine, twelve, and beyond. But just do the amount necessary to solve the problem.
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