What is EQ?
We have to start here on a post about EQ, a quick glance at what it is and what it does, but also the slightly lesser known concept of why this actually works and what it's actually doing to your audio signal. At a basic level, an EQ is a tool that is used to shape the frequencies of your song, or of individual tracks. It can be used to shave off unwanted frequencies and frequencies that clash with the other tracks, or it can be used to add more of certain desirable frequencies.
How does it actually work though? An EQ typically works because of a phenomenon called phase cancellation. Basically, if you invert the phase of an audio signal and then play it back with the original, the audio cancels each other and you're left with silence. By using filters, originally made up of electronics such as transistors and capacitors, but now in the digital world recreated with 1s and 0s, you can control the frequency range that you're playing back into the signal and only the selected frequency range will get phase shifted by an adjustable amount, which allows you to cut away frequencies. To add frequencies, a similar process is used but instead of adding phase shifted material you're just adding more of the unaffected signal.
This is important later because there are different types of eq and different phenomenon that you may encounter related to how the EQ is processing the signal.
There are many practical uses for an EQ, as a producer / engineer this will probably be one of your most used tools. Different types of of EQ bands (or shapes) include but are not limited to, bell, shelf, notch, and cut. The bell shape has a more gradual slope and is used to boost or attenuate (this is an industry term that means to reduce the volume) a range of frequencies anywhere on the spectrum. A notch is similar but with a much sharper slope meant for boosting or attenuating a very tight range. A shelf is on either the low end or the high end of the spectrum, and it boosts or attenuates starting at a specific range and increasing all the way to one end or the other of the spectrum. The cut filter (high cut or low cut) completely removes the high end or low end at a specified slope and starting at a specified frequency.
We use these filter shapes to sculpt the frequencies of each sound that is present in our music so that they fit together better. Some common issues that are solved with EQ include elements of the track having clashing frequencies, causing them to mask each other (meaning that you can't hear the sound very clearly), and the build up of resonance in certain frequencies that can be unpleasant to the ear, (this is when you have very sharp peaks). Often times the most painful area of resonance to look out for is between 3k - 5k.
A good practical tip on EQ is that if you attenuate a frequency and it makes your sound better, that is a good indicator that you're making a good move. On the other hand, you may be more likely to think almost anything you boost will make the sound better, even if it does not. This is because our brain is wired to think louder = better. Therefore, attenuating is often a more practical move. You can always apply make-up gain after you attenuate something, and then it will be as if you're actually boosting everything else except what you took away. If you just boost things left and right, you're more likely to just be making everything louder but not necessarily better. I'm not saying don't boost, just a reminder to be mindful of how our brains work and to boost with intention.
Something that you'll find a lot of advice to do on the internet is to low cut everything that is not a bass so that you don't end up with extra rumble in the low end and have a muddy bass. This is (to some degree) a good idea, however, I would argue that it is better to be mindful of what you're low cutting and only do it if you have a good reason to, (such as there is low rumble that you can see/hear in the track, in which case you will need to cut it) but don't just mindlessly low cut everything even if there's no low frequency present, and try not to stack a bunch of low cut EQ in a chain, because this can actually damage your signal. This goes back to the conversation in the intro about phase cancellation, and especially when you're affecting the low end, you're going to alter your signal perhaps more than you know. Below I will show a picture of a saw wave on an oscilloscope, and then show you what it looks like after applying a low cut filter (note that the low cut filter isn't actually even cutting out any frequencies, it's below the fundamental - which is the lowest frequency peak in the sound).
The first picture is just the saw wave with the EQ not doing anything. Looks how a saw wave should look, right? Well look at what happens in the next image when we turn on a low cut filter (not even cutting out any real frequency information). It's not even a saw wave anymore! If you try this test at home, you will hear a pretty noticeable difference.
This is why it is important to be weary of how much EQ you are applying and if you are putting unnecessary EQ, especially low cut EQ. Now, the Ableton stock EQ is what is known as a Zero Latency EQ, which is the easiest on your CPU processing but has significant phase shifting, which is part of why this phenomenon happens. There are other types of EQ that we will look into in the final section, Types of EQ, but first, let's get into some advanced practical uses in my favorite EQ plug in.
Advanced Practical Uses In ProQ3
Dynamic EQ is an extremely versatile tool available in many more advanced EQ plug ins, my favorite of which is FabFilter ProQ3. Dynamic EQ is essentialling combining a compressor with an eq, and it allows you to make dynamic boosts and cuts, meaning that the eq only boosts/cuts the frequency when the frequency of the audio signal crosses a certain volume threshold. You can adjust these settings within the EQ, and this is a great way to tame harshness that only happens every so often and to smooth out a track that has a lot of inconsistent frequency peaks. An example of this might be something like a vocal where the S's are all very harsh, but you don't want to just cut the frequency on the whole track because then the rest of the vocal will be too dull. In this case, using a dynamic EQ can cut the harshness only when it's getting too harsh without affecting it the rest of the time.
Similar to dynamic EQ, there is also sidechain dynamic eq, which is basically like a sidechain compressor. You use this the same as a dynamic EQ except instead of the threshold responding to the track the EQ is on, you can have it respond to another track, cutting or boosting it in response to what another track is doing. This is great for things such as ducking your guitar in certain frequencies when the vocal comes in, leaving room for the lead vocal to shine, as well as plenty of other similar situations where you want to dynamically create room for another element only when that element comes in.
The final thing I want to talk about with ProQ 3 is the visual referencing. This is an extremely useful tool where you can see the frequency spectrum of the current track as well as the spectrum of another track that you select in real time, which is great for comparing the tonal balance of your song to a reference, or seeing where there may be clashing frequencies between two tracks. To help identify this, the EQ even glows red where the frequencies may be clashing.
Types of EQ
These different types of EQ are mainly different ways that the EQ handles the audio signal, which has an effect on the phase issues we have talked about above. There are 3 main ones we will discuss briefly, and those are Zero Latency, Natural Phase, and Linear Phase.
Zero Latency EQ is the most common that we will see. The stock EQ in your DAW is almost certainly this type, and it is great for most utilities as it does its job and requires the least amount of processing power. There are certain times when this EQ can cause some complications, however, such as in the low cut issue that we saw earlier, and in some cases, depending on the type of audio you're dealing with, you might cause phase cancellation between tracks (some examples I've seen include multiple recordings layered together of the same sound, such as 2 mics recording the same snare drum). When you have very similar signals running together, you might run into this, but as electronic producers, it's very unlikely/uncommon. Just something to keep in mind, if you happen to notice something very unusual occur in the frequency when you apply an EQ. I'll link to the video explaining this phenomenon so you can check it out yourself.
Linear Phase EQ is another type of EQ. This EQ was made for the specific purpose of combating these issues listed above. If you run into something like in the video I linked, this type of EQ is likely your best bet. This is a more expensive EQ typically, although you have this option If you have FabFilter ProQ 3 (which, if you don't, I highly recommend this EQ). There is a caveat here, however. A common misperception is that linear phase EQ is better than a zero latency EQ. This is not the case. It is simply different and has a certain utility. There are downfalls of this EQ type to be aware of. The first you'll likely notice off the bat is that it requires massive processing power. Unless you have an extremely powerful computer, you probably can't handle more than a couple of these in your entire project. The second issue is that it does have an effect on the signal coming through in terms of the transient response. You may notice that on more transient sounds such as drums or plucks, the initial transient can get blurred when using this EQ. I recommend testing it out at home to determine yourself how it sounds and then make an educated decision on how/if you will use this EQ type.
If you have FabFilter ProQ 3, then you have 3 different options for EQ type, and the third of these is called Natural Phase. This is my favorite solution to the low cut problem we saw above. The natural phase has a different kind of algorithm than the linear phase and the zero latency, and kind of lands somewhere in the middle. You don't have such noticeable effects on the sound when you low cut it (although it is still imperfect), but you don't have any transient blur and the processing is more reasonable. It's a sort of best of both worlds, and I don't know exactly the nuts and bolts of what it does but personally I use this for my low cutting and low end work and go ahead and use zero latency for most other EQ jobs. Even with this EQ, I still have to emphasize it's not perfect and still affects your sound to some degree. I recommend doing some tests at home to see this first hand, but the TLDR is the less EQ moves you make, the more you preserve the integrity of the track, especially when dealing with low end.
Hopefully you learned something about EQ that will help improve your future productions, or at least make you more mindful of what you're doing and why!
Until Next Time,