EQ before Compression or Compression before EQ?

EQ before Compression or Compression before EQ?

Mixing can often be an arduous process. With such a vast array of resources available these days, aspiring mix engineers are often trying to find what the best practises are in order to get “that sound”. One of the more frequent questions I get asked is when to use EQ and when to use compression in a chain. You may have heard the saying: “Always EQ before you compress” - but that’s not always necessarily the case! The truth is, every mix should be treated uniquely. There is no right or wrong, however, certain scenario’s might often require certain practises. Let’s explore this further: EQ first then compression, compression first then EQ and even EQ then compression then EQ, how do we go about identifying when to use what?

EQ Before Compressor

Now then, when you record a track, there is going to be bottom end that you don’t want, a good starting point is frequencies below 100Hz. Adding compression before you EQ that out will most likely just amplify this, resulting in the dreaded “muddy sounding” track. Now imagine applying said affect to the total number of tracks in your project - 50, 60 tracks? Exactly. Use a high pass filter (EQ) before compression to free up a bunch of space for the low end to sit nice and pretty in the mix. (Remember, not every track needs a high pass filter!)

Keep in mind, placing EQ before compression will often have the effect of exaggerating the applied EQ, due to a phenomenon known as “frequency masking”. Ok, don’t be frightened, all we mean by this is that louder sounds (or louder frequency ranges within a sound) tend to draw the listener’s attention away from the less audible sounds. This can make the track "sound EQ'ed" without actually producing the specific frequency level changes intended.

Compressor Before EQ

So, the rationale here is that if you were to first apply EQ, let’s say in the 2KHz range, that boost could push the compressor in an unwanted way, and actually negate the change. For example, if claps are lacking clarity and presence, first apply compression to tame the transient, and then use EQ, (around 2KHz in this example), to help make them more apparent.

This technique will often result in more audible results, (and therefore fewer EQ artefacts). Essentially, EQ post compression will get the most change with the least EQ. Now let’s think of a compressor and EQ as one in-line unit. Placing the EQ before the compressor is like having a compressor with a frequency dependent Threshold. An EQ boost will send more signal at that frequency to the compressor, which in turn will react to this increase in level and try to control the output level by compressing more.

EQ Then Compress Then EQ Again

I use this approach a lot when mixing vocals. I’ll use a high-pass filter if there are any rumbly, muddy, boxy (pick your adjective) frequencies, to make sure that the compressor isn’t getting overloaded — then I’ll apply compression to taste, with another EQ boosting around 10-15k for the “air”. (See Plugin Alliance’s Maag EQ)

In conclusion

The combination of an EQ before compressor should be regarded as an entirely different animal than a compressor before EQ. The advantages and disadvantages of each are entirely dependent on the effect that your mix needs. The most important thing here is to make a decision based on the source material and move on, rather than fatigue yourself by worrying about “the correct way” to mix. In fact most compressors today, including digital ones, have an inherent tone which in itself can be used as an EQ. All things considered, this question is essentially unanswerable, like most things musical, results are subject to taste!

Homework!?

  1. Apply an EQ boost of 50 or 60Hz across an entire drum track to boost the level of the bass drum.
  2. Feed the output of the EQ into a compressor set on a moderate ratio of 4:1, threshold of around -10dB, and with a fast attack and release. The effect that this boost has on the compressor that follows the EQ, means the compressor will reduce the level of the entire drum track every time the bass drum hits.
  3. Now try swapping the order of the EQ and the compressor so that the compressor is placed before the EQ and listen to the low end!

Have fun & happy mixing!


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