Mastering 101: EQ Basics

Every Monday, we will be looking at one of these mastering topics. If you’ve missed one, click on the topic below to catch up:

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

This week, we look at EQ Basics.

In mastering, a really good EQ can do wonders. 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 is preferred that one uses a mastering grade EQ to do work on your masters. In my opinion, Fabfilter’s Pro Q2 and DMG Audio’s Equilibrium are the two EQs that I think are great for mastering. The latter, is my usual weapon of choice.

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

  1. Do not cut or boost over 3dB

    The general rule here is that if you have to cut or boost a frequency band over 3dB, 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 him or her) and talk about the frequency spectrum in question and see if he could fix it in the mix.

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

  2. Use Wide Qs

    It is a fact that wider Qs (wider bandwidths) sound more musical than narrow / surgical EQ 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.

Before we can start EQ-ing, it’ll be good to know the different types on EQ and its pro’s and con’s. This will educate us to use the right type of EQ at the right time.

  1. Minimum Phase EQ (IIR)

    • Minimum phase EQ’s are your typical analog-type modeled EQ.
    • The Pros:
      • It is generally a low latency EQ. This means, it does not hog up CPU resources.
      • It has a familiar sound – models analog EQs built from resistors and capacitors. You hear them all the time in your amps, analog mixing desks, outboard EQs, etc.
      • It does fantastically well with low-end frequencies. Boosting or cutting low end with minimum phase EQs does not muddy the low end at all.
    • The Cons:
      • There’s a small phase shift that varies with frequency whenever it is cut or boosted. Thus, extreme cut or boosts, especially in the higher frequencies, can pull apart the time alignment of the frequencies and as a result cause a “smearing” effect. Clarity will be affected and probable distortion would occur.
      • Do note, the resulting distortion may sound like its brighter and can be used as a creative effect.
  2. Linear Phase EQ (FIR)

    • The Pros:
      • The latency and phase shift for all frequencies are the same. Therefore, one can perform extreme cuts/boosts without pulling the waveform apart.
      • Extremely smooth highs! Offer’s great clarity at the top.
    • The Cons:
      • High latency and CPU resource intensive. You often can hear an audible delay with a linear phase EQ. However, most DAWs should have delay compensation to help counter this.
      • Not as natural sounding as minimum phase EQ for the low end.

Putting our Knowledge into Practice

Now that we know what our general guidelines for using EQs are, here’s some practical steps to get you going

  1. Work in 0.25dB increments

    • Remember, mastering is all about subtle moves. While remembering to use wide Q’s, try to also work in 0.25dB increments and listen carefully to the changes. Sometimes, the changes are felt and not heard.
  2. Know your Frequencies


    • Knowing what frequency ranges to cut or boost is critical to mastering. If a mix is muddy, try cutting the upper-bass band around 250Hz or take out a little of the low-mids. Sometimes adding highs frequencies (I often use high shelves, hardly any bell shaped EQs in the highs), will often help brighten up a mix without the need the cut low-mids. Remember, one move (cut or boost) is relative and affects another.
  3. Combine Linear and Minimum Phase together

    • We know the advantages of both linear and minimum phase EQs. What I often find myself doing is that I would use a minimum phase EQ to work on the low end and low-mids of a mix and then slap on a linear phase to tweak the mid, upper midrange and high end of the mix. Combining the both often gives pretty desirable results!
  4. Use Mid / Side Processing

    • Mid / Side processing (MS) can be a powerful EQ tool. Both Fabfilter and DMG Audio EQs offer MS capabilities within the EQ itself.
    • Use MID processing to EQ a vocal in a mix. If you find a vocal needs clarity, use a linear phase EQ to bring up the brightness and clarity around 2-4Khz.
    • Use SIDE processing to EQ reverbs and detail in the side channels. I often find myself adding a touch of high shelf (8Khz and above) to bring up some detail in the sides of a mix so that the mix would appear wider.
  5. Do not Over-Process

    • I cannot stress the importance of not over-processing. We all have the tendency to EQ way too much and go over board. Take breaks when mastering. If you think that you are unsure of what you are doing, move on to another song first.
    • Remember, do not spend longer than 25 minutes to master a song. Anymore than that, you are 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 this week. Feel free to leave comments / questions and we’ll do our best at answering them.

Next week, we discuss mastering compression.

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February 15, 2016

Reuben Raman Product Marketing Manager at Splice