EQ – cutting vs boosting

Never boost, always cut. Or not…

EQ is one of the most important tools available to an engineer (second only the the volume fader). It can be quite a complicated tool to use, and it’s not always easy to know how to apply it. Sometimes advice is given that ‘cutting’ (reducing the level of a frequency band) is inherently better than ‘boosting’ (increasing the level of a frequency band). Inevitably, the converse view is the cowboy “if it sounds good, it is good”. Both camps rarely explain their reasoning, so how do you decide for yourself which approach to take?

The fundamental role of EQ is to change the tone of a sound. Whenever gain is applied to an EQ band, part of the sound is being changed. For the most part, this change only occurs at the area around the EQ band – the rest of the frequency spectrum remains unchanged.

  • When reducing the gain of band (‘cutting’), the changed part becomes quieter.
  • When increasing the gain of a band (‘boosting’), the changed part becomes louder.

Generally, reducing gain sounds cleaner because the changed part is de-emphasised in comparison to the unchanged parts. As a result, the natural character of the sound remains more intact, and the processing sounds more neutral and transparent. This is a useful approach to take when you want to maintain the general character of the sound, and the EQ is mainly being used to fit the sound in the mix. This works best when the original sound is well-recorded and already has an appropriate character for the mix.

On the other hand, increasing gain makes audio sound modified because the changed part is being emphasised over the unchanged parts. As a result, the changed part stands out and draws attention to itself. This approach works best when you want to change the character of a sound.

Of course there are exceptions to the rule. Often it’s possible to boost the top end of a sound in a way that sounds natural – only brighter. Similarly, it’s common to use dramatic low pass and high pass filters to make a sound radically different.

Personally, I almost always find that ‘boosting’ sounds wrong. The only exception is the top boost mentioned above – adding more high-frequency energy often doesn’t affect the general character of a sound. Still, I probably apply ‘cuts’ about 80% of the time I use EQ. 

Ultimately though, the question of how to apply EQ should be proceded by the question of what you want to achieve.

-Kim.

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