EQ – What’s the Point?

I don’t have enough fingers and toes to count the number of articles, chapters in books and blog entries I’ve read about “How to EQ Like the Pros”, “5 EQ Mistakes Not to Make”, “Crucial EQ Bands to Help with Your Mix”. Whilst I’ve definitely picked up some good tips that I apply when mixing, some of the pieces I’ve read over the years neglect a key point relating to this versatile tone sculpting tool – why apply EQ to a track or mix in the first place?

First Principles

Taking a step back for a moment, let’s think about what equalisation (yeah that’s what EQ stands for) is all about. As we’ve talked about before on the blog, sound is a vibration through a medium that can be detected by some kind of receptor. For humans there is a range of vibrations that our ears can detect and decode – roughly 20 Hz to 20,000 Hz. Equalisation is one of the tools available to us to manipulate how much of a certain frequency or specifically which frequencies in this audible range we hear, or equally, don’t hear.

If you take a look at the front of your Neve 1081 that Santa gave you for Christmas last year you’ll see three types of EQ filter parameters – pass (or cut), shelf, peak.

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Pass / Cut – The two terms are often used interchangeably and mean the opposite of one another. A low pass is a high cut. A high pass is a low cut. For the rest of this article I will refer to them as pass filters.

These filters are effectively eliminating frequencies (i.e. cut them out) below / above the cut off level you dial in. Put another way, they allow any frequency above / below the cut off frequency to pass through.

Some equalisers allow you to choose how steep the cut off is by selecting the number of decibels of attenuation per octave. A low number (e.g. 6 dB / octave) has a gentler roll off and is more similar to how the human ear works. A high number (e.g. 48 dB / octave) means a more extreme cut and is good for removing unwanted low frequency rumbles when you definitely don’t want them interfering with your sound, like the tractor that decided to drive past the studio during your vocal take.

Shelf – We now move into the world of frequency boosting and attenuation. A shelf filter allows you to do this for all frequencies below / above the cut off frequency for low / high shelves respectively.

On some EQs you can select by how much you boost or attenuate the frequencies. On others you only have the option to select the frequency of the cut off and whether it boosts or cuts.

Peak – The most tightly focused of the filters, peaks allow you to select a single frequency and boost or attenuate it to taste. These also capture frequencies either side of the selected frequency centre and apply the amplitude lift or cut to them as well, although to a decreasing amount as you move further away from the centre.

You can sometimes select how wide the range of frequencies captured by a peak filter is by adjusting the Q. Wider peak filters have a low Q value (e.g. 1), more narrow peaks have a high Q value (e.g. 8).

Now that we know what we’re working with, what the heck are we going to do with our EQ and more importantly – why? I’ll now go through some key things to have in mind when unleashing an equaliser on your instrument or mix.

Tone Shaping

You may simply want to focus your sound in between certain key frequencies. The trademark Robbie Shakespeare bass sound is pretty much limited to frequencies in the lower end of the audible spectrum. This can be achieved directly from your instrument on some basses, or on the amp by rolling off (i.e. attenuating) the mid and high frequencies on the relevant tone dials. If you’re doing it “in-the-box” or on playback from your tape reel you can add an EQ plug in or send your signal through an outboard EQ unit.

Try fiddling around with the different tone knobs you have available and notice how it changes the feel of your sound. You might find something you like ready for your next gig or recording session.

Masking

In audio terms, masking is when one sound gets in the way (or blocks from our perception) another sound. This can be quite common between kick drums and certain notes in a bass line where their fundamental frequencies are close to each another. We refer to this as frequency masking. If you want all elements of your mix to sound clear, this kind of masking is something you want to either avoid or effectively manage. One possible way of doing that is through the application of EQ adjustments to tracks coupled with some side-chain compression.

Here’s a neat approach we picked up from Dave Pensado and Jaycen Joshua about making copies of a bass line and splitting this into three frequency bands (more on that below) using high and low pass filters. By then applying side-chained compression to the low frequency copy so that every time the kick plays, the low frequency element is compressed, this effectively reduces masking of the kick by the low frequencies.

Give it a try and see if it can make a difference to your mixes.

EQ bands

Having spent some time as a youngster mucking around with mixing in a DJ context, I had become a little fixated on lows, mids and highs (well actually lows and mids – my first mixer only had two EQ bands). When I progressed into the “other” type of mixing, I brought that mentality with me and tried to apply some pretty arbitrary rules about EQ bands. My thinking went along the lines of:

  • Everything below 200 Hz is low;
  • 200 Hz to 2 kHZ are low-mids;
  • 2 kHz to 6 kHz are high-mids; and
  • Everything above 6 kHz is high

It’s easy to find yourself stuffing sounds into these boxes without giving it much more thought. Now don’t get me wrong, I am absolutely not knocking this approach, in fact this kind of mentality is very useful as it helps to focus your attention into areas where you can make the biggest difference to your mix quickly. Let’s face it, there’s just so much you could be doing, you’ve got to narrow it down a bit. However, again this kind of thinking was not answering that key question – what’s the point of apply an EQ adjustment in the first place.

Of course, using fixed numbers like the above example doesn’t take into account the key of the song you are playing in, the instrumental arrangement and feel you are trying to achieve with your mix. All of these factors will have an impact on where the boundaries between the EQ bands lie. By all means think in terms of a limited set of EQ bands but allow yourself to flex the borders between them based on what you’re trying to achieve with your mix.

Simultaneous Sounds

There’s a lot of discussion around the school of thought that the human ear can only really distinguish three distinct sounds simultaneously. Anything more than that and it all starts to get a bit messy and confusing for our poor little brains. Now this doesn’t mean it’s time to sack the keyboard player because the drums, guitar and bass are all you need. By that logic you’d be telling the lead singer to pipe down too! What this means in practice is that there should only be three “feature” sound elements at any one point in a track.

Going back to our earlier thinking about EQ bands consider what the three key elements of your song are for each part of the song. Do they sit in the same EQ band as one another or are they spread across the audible spectrum? If you find they’re sitting close together then you may way to consider using some form of EQ manipulation to give each of the sounds their own space in the mix. Sure, you could achieve this through panning, placing the sounds on opposite sides of the stereo field, however that could all be in vein if your mix is played back in mono (uh-oh masking!). Whilst trying not to totally change the sound of your parts, try out carefully chosen EQ cuts give the simultaneously playing parts their own breathing space.

Where feature elements of a track sit in different parts of the frequency spectrum don’t think you’re off the hook as far as EQ adjustments go to get greater clarity in your mix. It’s good practice to apply high pass filters (i.e. cut out the lower frequency elements) of any tracks that don’t have a low frequency element that plays an important part in the musical arrangement. Try this on your vocal and guitar tracks for example to clear space for your bass and kick to shine through that bit more. You would be surprised about how extreme you can get with your high pass filters when applying them to cymbals and high hats.

Apply EQ With Intention

I mulled over this for a while, what’s the one big takeaway from this post on EQ. I started by posing the question EQ – What’s the Point? The answer to that is, there are many points as to why you might apply EQ. The important thing is that you understand what that point is. I would encourage you to think about what you intend to achieve when applying EQ adjustments and let this guide your decision about what specific adjustments you then apply. In short, apply EQ with a specific intention in mind.

Now get out there any make some music!

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