I was mastering an EP recently and I really thought I'd done a decent job on the mix. I set up the tracks in order and found the correct levels for all of them, making sure they all sound equally loud and such. Then I got to work and set up my mastering processors, which are basically just EQ and compression. After a few EQ tweaks here and there, a little bit in the lows, a small boost in the highs, a subtle dip in the mids, you know the drill. Well, after a while I started A/B'ing the before and after.
And I was floored.
It was incredible how much of a difference a few cuts and boosts here and there could just clean up my mix. A mix I thought was actually pretty good to begin with.
And I'm not talking about massive boosts or serious EQ tweaks. I'm talking simple, broad Q boosts of a few dBs.
2 dB tops. But that made all the difference. Now my mix was more open, had less muddiness and just cleaner in every aspect.
That's the power of EQ for you.
In the following tutorial I'm going to go over a few quick tips for EQ'ing during mastering. Remember that mastering is a subtle art. Broad EQ changes are more important than surgical EQ changes. They certainly have their place, but err on the side of wider to be safe.
Filtering - One of my go to starting points is a high-pass filter. I set it and forget it at 32 Hz. It doesn't do much, but it's more of a preventive measure if there is a lot of sub-bass going on in the mix. Sometimes it does actually tend to clean up the low-end a little bit, even thought you shouldn't really be able to hear those frequencies. I guess it's because it frees up the higher bass when it's not bogged down by the subsonics. Or something like that.
Tonic Note – If the bass seems “fluffy” or badly defined it can be a good idea to find the tonic, or root note, of the song and boost that in the bass. That way you bring up the bass line but you're not just boosting a random low frequency. You're doing it musically and it might fit gel better with the rest of the mix than if you'd just boost the first low frequency you find.
Point of the Kick Drum – Even if you think the mix has a lot of bass, you might not be well off if you just cut the low end in its entirety. Doing a low-shelving cut is fine if everything needs to be lowered in the bass frequencies. But the fact is, sometimes you lose the kick drum this way. You might even only hear the click from the beater, and it's lacking thickness because you cut it too much.
This screenshot is a little exaggerated, but I think you can get what I'm talking about. You might need to lower the bass because it muddies up the entire mix, but by adding a slight bell curve boost for the kick drum you can surgically remove the bass while cosmetically enhance the kick. How's that for a metaphor?
Boominess – If you're having thickness problems that can't be fixed in the low end, maybe your low-mids are to blame. A mild, low Q cut in the 200–250 Hz is a very good way to open up a mix that you feel is too cluttered or lacks definition. By its very nature, a cut in the low-mids gives more room and accents the high-mids. That's the subjective nature of subtractive EQ. Cutting a certain frequency subjectively increases (or boosts) another frequency.
Guitars and Snare – More definition from the snare and guitars is found smack dab in the middle of the mids, or around 500 Hz. Beware that you will have a hard time having one or the other. You usually have to settle for both. Whether you think that your snare needs more definition or the guitars need more thickness, they sometimes go in hand in hand. Since it's a mastering project and you should only have a two-track master, boosting those frequencies will bring out all the characteristics of each instrument that resides there. In this case, a heavy dose of the guitars and snare. It can also make the whole mix sound a little cardboard boxy so be careful.
High Mids and Air
Presence – Be aware of adding too much presence in the 3–5 kHz. Sure it can sounds great and brings up the vocal a lot but it can have the adverse effects of doing too much. Once I had to go back and lower my boosts because they were disproportional to the rest of the mix, and the vocals were way louder than anything else.
Highs – Nice air EQ can spice up the dullest of mixes. Be aware that you're boosting all the highs, and if you have a particularly loud drum mix you might be boosting the cymbals too much in proportion to the rest.
Brightness – Sometimes your mix is just too bright but you don't want to compromise the instruments. If that's the case, try a high-shelving EQ with a Q of 1 and start it at 20 kHz. Cut a few dBs and move it down until you feel you've tamed the brightness.
Above is a hypothetical example of an mastering EQ curve if we followed a track that had all these problems. Of course, every song is different and every mix needs a different mastering approach. Trying out these few frequency areas is a good starting point, and I wouldn't be surprised if your mix would start sounding a lot better after applying some of these boosts or cuts.
There's just something about the general, across the board mastering EQ that can make a mix sound so much cleaner.