Practical Home Mixing Tips #3: Subtractive EQ

I often get asked about using EQ, and people are most interested in ways you can use EQ to solve problems and make your mix clearer. Proper use of EQ is truly one of the best tools to take your home recording from a demo to a pro sounding mix. So let’s dive in!

In my mind there are two main kinds of EQ:

1) EQ’ing for colour/vibe/character. This is your standard turn up the treble knob to make things brighter etc…

For this I recommend a plugin that emulates some kind of analogue EQ, as this tends to add more character. If you use Logic X like me, the Vintage EQ collection is amazing at this. Below is the Neve console emulation which works magic to add chunky-ness and energy.

Console EQ

2) The second kind I would call technical EQ. This solve problems, clears away unwanted and wild frequencies and makes space for each instrument in the sonic landscape. The most common tool here is subtractive EQ, and the main topic for today’s blog post. For this you want to grab a graphic EQ that allows finite control over multiple frequency bands.

Subtractive EQ simply means lowering frequencies, and in many cases removing instead of adding can sound clearer. For example if you want a sound to be brighter, why not remove some low end, and just boost the volume? Adding a bunch of high end can sometimes sound artificial and harsh.

A common application of subtractive EQ is using a high pass filter set to somewhere between 60-100hz on everything that isn’t a low sound. (i.e. everything that is not a bass part or kick drum), this is a quick way to get a clearer low end on the overall mix as it removes the unwanted noise that exists in that range. Ever listen to a guitar part with with everything above 60-100hz rolled off? Yeah, just noise down there. This of course doesn’t work perfectly in all applications and like anything with mixing, it’s just a starting place. In certain mixes having some untamed low frequencies can add an essence you may not want to lose.

A high pass filter looks like this:

Here are some examples of using subtractive EQ to solve more specific problems.

Example 1: The Obnoxious Telecaster

Here we have a very rude telecaster. Take a listen and you’ll hear some high frequencies that aren’t really part of the chord being played, it almost sounds like feedback behind the main sound.

Now, if this was the only guitar part, I might leave it because all those harmonics add energy and excitement. But for a multi track pop song this beast must be tamed! Sitting in a track with other guitar parts around it, the errant high frequencies will cause frequency build up and a harsh sounding top end in the overall mix.

The image below shows the EQ fix for this. Firstly, we’ve applied the high pass filter mentioned above to get rid of low end noise. Most importantly though, we have isolated the frequencies causing the errant harmonic sounds. Each of the EQ bands below has 3 parameters, frequency, volume and Q. The “Q” is the width of the band, represented by the little mountain or valley shape. Start by grabbing one of the high frequency bands, making a very focused Q (between 50-100) and turning the volume up to over 15dB for that band. This will sound horrible, and if the songwriter/artist is in the room, tell them to plug their ears. You can now sweep back and forth using the frequency control until you hear the offending frequency (this will be obvious, as it will jump out like crazy). Now that you’ve isolated the problem, turn it down until it’s just low enough to disappear in the mix. Here we’ve subtracted 595, 1140 and 1830hz. We also ducked the top end using a high shelf. This example shows frequency dips of -20db or more, which would be considered too much by some, but I’ve made them big for illustration purposes.

Telecaster EQ

Here’s the same Telecaster with the EQ applied. Doesn’t that sound more pleasant?

Example #2: Basketball kick drum

Here we have two stereo room mics on the drum kit. They are summed down to one channel using aux routing (see Blog post #2 for more on this). There is kind of a swampy low end, which we can fix with the good old high pass filter, but also the kick drum has a mid-range ring to it that sounds like someone bouncing a basketball in the recording studio. This is not great, and is adding mid-range noise to the overall mix.

For the fix, we’ve used the same technique of sweeping around with a very focused Q and made a little valley where the offending sound lived. This was mostly at 690hz (ultimately using a slightly wider Q of 2.6) and a small cut at 426hz.

Here is the same sound with the EQ applied. You can hear a tighter overall drum kit and that high mid, basketball bouncing sound is gone.

As a final note, I should point out that overdoing it with subtractive EQ and removing every frequency that bothers you can end up with an unnatural and lifeless sound. Very useful energy and emotion sometimes exists in those wild frequencies. In the end whatever sounds best to you is the ticket!