4 Tips for EQ in Mastering

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So, you want to get into mastering, and you’ve found yourself here. Welcome. Soon we will cover topics like compression and limiting—mayhaps, monitoring and room treatment to boot—but first, we’re going to give you a few insights into a process with tons of tonal impact on the final master. I speak, of course, of equalization.

The General Approach

It is often said that EQ adjustments in the realm of mastering are usually subtle. If you watch a tutorial or stand over the shoulder of a mastering engineer, you’ll frequently notice minute changes, such as a 1-dB cut of 350 Hz to notch out a little low-mids, or a slight high-frequency shelf of 0.5 dB at 8 kHz to bring out some sheen. Such seemingly small changes accomplish a great deal, and keeping oneself largely to making these changes leads to discipline, ear training, efficiency, and all-around sonic improvement.

First, a drastic cut or boost can alter the whole quality of the mix, and this is not desirable; with very few exceptions, the mastering engineer’s job is not to fix a sonically inferior mix, but to make the mix gel with other commercially released material of a similar genre—or other mixes on the same single, EP, album, mixtape, playlist, or whatever you might call it in the near future. When you make drastic changes to a frequency range, the whole character of the mix changes, because you are affecting whole swathes of instruments in that frequency band.

Furthermore, subtle adjustments help the mastering engineer fight against initially seductive timbres and, thus, preserve the objective mindset necessary for mastering. Mixing engineers will recognize the following phenomenon: An effect that seems wonderful at the outset can have an ear-fatiguing effect later. The same holds true for mastering, and so mastering engineers must maintain a balanced view of the song in its entirety, avoiding straining their ears.

So, you’re often better off hedging your bets. I often find that over time, my ear comes to recognize that a 1-dB change, rather than a 4- or 5-dB change, accomplishes what I need without introducing what I don’t.

This isn’t to say that bold sweeping moves aren’t taken; it’s all about context, after all. Quite often on a thin mix, for example, I’ll use a boost of four decibels or more with a wide boost, but well below the intended frequency, so that its slope downwards raises the frequency ever so slightly, with a minimal effect on the subsonic low end (and this can be high-pass filtered if need be).

Still, these tend to be the exceptions rather than the rules. Try to keep your moves to under a decibel, or two at most, when you’re just starting, as a freedom-in-limitations exercise. You may love the results.

Linear Phase versus Minimum Phase

The analog EQs of yesteryear introduced a pleasant distorting effect called phase distortion, wherein the selected, manipulated frequency would be delayed ever so slightly from the rest; the cumulative effect of this can lend wonderful character to an instrument. Indeed, the je ne sais quoi that makes each EQ desirable can be traced to this phase shift, to some extent. However, this coloration can also be a detriment when trying to make clean, surgical changes.

With the advent of digital came linear phase EQs, which use time-aligning digital tools to ensure no changing in timing between affected and unaffected frequencies. This results in a cleaner, more colorless sound; it’s often said that linear phase equalization feels almost like raising or lowering a fader on a frequency band, rather than tweaking its drive-inducing gain pot (which would be more like the analog model). Though you’ll get a more natural, and some would say more open, sound, the tradeoff can be artifacts that result from the time-aligning process. Pre-ringing can be a particularly nasty one, and an example of it can be heard below.

In mastering, we slip between both practices—EQ’ing for vibe and EQ’ing with a natural, invisible hand. This means you should get familiarized with the sonic signatures of both processes. As a practice, take a digital EQ that has both minimum and linear phase modes (FabFilter Pro-Q 2 has both, for example), instantiate a large, audible boost in various frequency ranges, and compare the effects of minimum phase with linear phase. Don’t just listen to the frequency in question however; try to focus, also, on the rest of the mix, what the EQ change does to it. Listen for the effect on the mix’s perceived density, level, and clarity.

FabFilter Pro-Q 2 - Linear-Phase Mid/Side EQ Plug-In for Mac and Windows

Mid Side Tricks with EQ

M/S—standing for Mid/side—is a powerful concept when it comes to mastering. Now, the science behind M/S cannot be explained in the space we have, but the effect of M/S can: M/S seems to give us the ability to separately process center-panned information (the M for middle), or conversely, to focus solely on the far left and far right (S for sides). I say “seems” because that definition is simplistic and not strictly true, though it often appears to be true.

So, let’s talk about things we can do with M/S equalization. The most obvious tricks include: Curtailing meddlesome bass information on the sides, which isn’t often necessary to the mix; taking out unflattering resonances or blooms in the bass instruments, which tend to reside in the mid channel; and mitigating harshness in the cymbals, which are often found in the sides.

These are all wonderful techniques when they’re called for, but I’d also like to highlight a more creative mastering application of M/S equalization. Many are the companies who sling their stereo-widening tools like pharmaceuticals in the fight against mix-malaise—but with very few exceptions, these tools are unnecessary. You can achieve widening effects with M/S EQ alone! For instance, if you want the mix to feel a little wider overall, you can go into a plug-in like FabFilter Pro-Q 2, flip it into M/S mode, and change the panning to favor the sides by one decibel.

Conversely, you could instantiate a 0.5 dB tilt-shelf on the sides that boosts everything above 200 Hz and attenuates everything below 200 Hz by a fractional amount; this would achieve a subtle widening effect. You can use widely ranged parametric boosts to widen elements of the mix by frequency, too. Many of the effects offered by so-called stereo width plug-ins are achieved with far greater precision—and thus, far better effect—with an EQ in M/S mode. You won’t get the special analog warmth of spatial widening with a Portico II Master Buss Processor, or the UAD equivalent thereof, but you will be able to achieve widening techniques.

Rupert Neve Designs Portico II Master Buss Processor

EQ’ing in the Ecosystem

In the realm of mastering, all the processes are interactive; how you EQ will influence compression and limiting decisions down the line. Always keep this in mind when you’re equalizing. For instance, if you place the equalizer before the compressor, and you want to boost the lows of a particularly thin mix, this will change the behavior of the compressor, causing it to clamp down when it hears the louder, lower frequencies. Of course, this might be mitigated if the compressor has a sidechain filter to keep it from reacting to low frequencies, but the compressor would still be affected.

EQ’ing in mastering is a yin/yang game, with frequency boosts in one range impacting the perception of a corresponding frequency band in an opposing manner. Thus, boosting the lows will have a dulling effect on the highs. In the context of our ecosystem, such a boost may cause the compressor to react differently, as it might’ve detected the louder high frequencies if left untouched.

If you reverse the equalizer and the compressor positions, then you’re dealing with the compressor as a tonal shaper in and of itself, its flattening effects, or its coloration—if the compressor is, indeed, a color piece. Therefore, whichever way you choose to go, I recommend that you master with all processes inline. We’ll cover how best to set up your processes in later mastering-centered articles, but have your equalizer, compressor, and limiter on from the get-go; this will save you from having to re-tweak a whole bunch of settings once you switched a compressor into the chain halfway through.

Conclusion

These are but a few of the considerations of the equalization mastering process. There’s simply too much to cover in one blog post. However, these concepts are a great place to focus your initial attention when acclimating yourself to the discipline. If you read this article and find yourself hungry for more tips on equalization in the mastering process, don’t hesitate to post your questions in the Comments section and let us know!

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