Mastering 101: EQ Basics

In mastering, a good EQ can do wonders.

This post is the second article in an introductory guide to mastering. If you’ve missed an entry, click on any topic below to catch up:

  1. What is mastering?
  2. Signal flow & metering
  3. EQ
  4. Compression
  5. Limiting
  6. Preparation

In this entry, we look at the basics of EQ.

1. Getting started with EQ

EQs are used to balance out the frequency spectrum of a mix, fix harsh tones, and make things sound clearer and more detailed. That being said, it’s preferable to use a mastering-grade EQ to work on your masters if possible. In my opinion, FabFilter’s Pro Q2 and DMG Audio’s Equilibrium are two EQs that are great for mastering. The latter in particular is my usual weapon of choice.

Before we dig deeper into EQs, here are two power-user tips for you to keep in mind:

1.1 Do not cut or boost over 3dB
If you have to cut or boost a frequency band over 3 dB, it means there’s most likely a problem with the mix. The best way around that is to speak to the mix engineer (if you have access to them) and talk about the frequency spectrum in question and see if they could fix it in the mix.

Another pro tip is to set the range of your EQ to show no more than 9 dB. What we see on our EQ curves inevitably affects the way we hear.
From the images above, you can see how the range affects the way the EQ curves look, despite both of them having the same amount of boost and cut. Although we should definitely be using our ears and not our eyes, having a graphic representation that keeps you within certain limits is always a good idea. And since you should not cut or boost more than 3 dB while mastering, setting an EQ range that is lower will definitely be helpful

1.2 Use Wide Qs
EQWider Qs (synonymous to bandwidths) sound more musical than narrow or surgical bandwidths. Thus, I recommended that while mastering, you should use try using a wider Q and working on broad strokes rather than notching out resonant frequencies.

2. The different types of EQ

Before we can start EQ-ing, it’ll be good to know the different types of EQ and their pros and cons. This will allow us to use the right type of EQ at the right time.

Minimum phase EQ (IIR)
Minimum phase EQs are your typical analog-type modeled EQ.

  • The pros:
    • It’s generally a low latency EQ, meaning it doesn’t hog up CPU resources.
    • It has a familiar sound, modeling analog EQs built from resistors and capacitors. You hear these all the time in your amps, analog mixing desks, outboard gear, etc.
    • It does a fantastically job at handling low end frequencies. Boosting or cutting low end with minimum phase EQs doesn’t muddy the low end very much at all.
  • The cons:
    • A small phase shift occurs whenever a frequency is cut or boosted. Thus, extreme cuts or boosts, especially in the higher frequencies, can pull apart the time alignment of the frequencies and result in a smearing effect. Clarity will be affected and distortion may occur.
    • That said, the resulting distortion may create a brighter sound that can at times be used as a creative effect.

Linear phase EQ (FIR)
Linear phase EQs were developed by programmers to combat the smearing effect of minimum phase EQs.

  • The pros:
    • The latency and phase shift for all frequencies are the same. Therefore, you can perform extreme cuts and boosts without pulling the waveform apart.
    • They allow for extremely smooth highs and great clarity at the upper extremes of the frequency spectrum.
  • The cons:
    • They tend to be high latency and CPU-intensive.
    • You can often hear an audible delay with linear phase EQs. That said, most DAWs should have delay compensation to help counter this.
    • They’re not as natural-sounding as minimum phase EQs for the low end.

3. Putting our knowledge into practice

Now that we have some general guidelines for using EQs, here are some practical steps to get you going.

3.1 Work in 0.25 dB increments
Remember, mastering is all about subtle moves. In addition to using wide Qs, try to also work in 0.25 dB increments and listen carefully to the changes. Sometimes, the changes are felt and not heard.

3.2 Know your frequencies

eq-cheat-sheetKnowing what frequency ranges to cut or boost is critical to mastering. If a mix is muddy, try cutting the upper-bass band around 250 Hz or taking out a little of the low mids. Sometimes adding highs frequencies (I often use high shelves over bell shaped EQs in the highs) will help brighten up a mix without the need the cut any low mids. Remember, one move (a cut or boost) is relative and affects the other.

3.3 Combine linear and minimum phase EQs
We now know the advantages of both linear and minimum phase EQs. I often find using a minimum phase EQ to work on the lows and low mids, and then slapping on a linear phase EQ to tweak the mids, upper mids, and highs – combining their respective strengths often delivers pretty desirable results.

3.4 Use mid / side processing
Mid / side processing (MS) can be a powerful EQ tool when used properly. Both FabFilter and DMG Audio EQs offer MS capabilities within their plugins.

Use mid processing to EQ a vocal in a mix – if you find that a vocal needs clarity, use a linear phase EQ to bring up the brightness around 2-4 kHz. Use side processing to EQ reverbs and add detail in the side channels. I often find myself adding a touch of high shelf (8 kHz and above) to bring up some detail in the sides of a mix so that the mix appears wider.

3.5 Don’t over-process
I can’t stress the importance of avoiding over-processing enough. We all have the tendency to EQ way too much and go overboard. Take breaks when mastering. If you’re unsure of what you’re doing, move on to another song first.

In my opinion, you should refrain from spending longer than 25 minutes when mastering a song. If you’re spending significantly more time than that, you’re most likely over-processing.

Lastly, always check your master against the mix. A/B it thoroughly and make sure your master is complimenting the mix and not destroying it.

That’s all for EQ – in the next entry, we’ll focus on compression.

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February 15, 2016

Reuben Raman Product Marketing Manager at Splice