What is EQ? Simple Explanation with Audio Examples

If you want to be a musician or even just someone who understands music and the language, there are certain terms that I feel no one really explains. For example, when someone says that something sounds wet or crunchy or they say the mix is off, what does that even mean? I'm going to explain all of this to you in the simplest way I know how, and each of these elements deserves its own video, so make sure you subscribe if you want all the answers. We're going to start with a big one. It's called EQ, but before we begin, I need to specify that in this video, I won't be demonstrating how to use EQ, rather simply what EQ is. But first, welcome to Music Theories. This is a channel dedicated to all things music, music theory, and music history. I want to bridge the gap of understanding between non-musicians and amateur musicians, and professional musicians, and so on. Make sure to subscribe for more content and hit the notification bell to know when the next video is out. Also, thank you so much for 10,000 subscribers. This is a huge milestone and I'm thrilled and flattered to have made it to this point. I am so appreciative to all who have watched, shared, liked, and subscribed. Thank you so much. Let's start with the basics. EQ is short for equalization. In music, this is the process of adjusting specific frequencies to highlight or reduce certain qualities in the sound. To understand this concept deeper, I recommend watching my video on pitch, tone, and note, as well as the episode on consonance and dissonance. These videos are not required to understand the content in this video, but will definitely help you internalize the idea. To recap, music itself is sound, obviously, and sound is vibration in the air that creates different types of sound waves. Within our systems of music, we as humans have decided which frequencies are pleasing to our ears and which ones are not. This also changes based on context. In western music, it's been widely accepted that the sound wave with a frequency of 440 Hz is the note that we call A, or more specifically, A4. So our music is made up of frequencies that are relative to 440 Hz. You may have seen on your car radio or even some of your music apps that there are settings where you can adjust the overall EQ of your playback. Usually, these are categorized by genre, so if you listen to mostly classical, you might select the classical setting in the EQ, and in theory, this should give you the optimal listening experience. These adjustments are usually very simple, something like a boost in the mids or the bass, or a reduction of the treble, and so on. But I guess today some car radios are a little more customizable. But when it comes to creating music, EQ is way more in-depth. In fact, it's not unusual for an engineer to use EQ on every instrument in the song. But why and how? Since sound isn't necessarily something we can see, we use a useful tool called a visualizer. These charts specifically represent the frequencies that can be heard by the human ear. The horizontal axis represents the frequency of the pitch, the lowest being roughly 20 Hz, and the highest being roughly 20,000 Hz. And the vertical axis represents the increase in the signal level of the pitch. This is measured in a unit called the decibel, often depicted as dB. In this case, the term is being used to represent the increase in the output signal when compared to the input signal. Many people use decibel to describe the volume of the pitch, though that's not technically correct. The decibel unit in music can be a little confusing and sort of changes based on context. The unit, dB, in general, depends on a reference point, and its function changes based on that reference point. I'll eventually make a separate supplemental video explaining the different functions of the decibel in music. But let me get back on track here. So the horizontal line refers to the frequency, and the vertical to the decibel level, which is zero decibels when flat. When it comes to EQ, specifically digital EQ like I'm using, the decibel is used to measure the boost or the cut made to specific frequencies. More on this in a bit. The spectrum of frequencies on the horizontal axis of this graph can be grouped into different bandwidths. These are the more opaque lines on the visualizer. There's an inconsistency on the internet with the ranges of each bandwidth. But here are the numbers according to The Mixing Engineer's Handbook by Bobby Ozynski. Sub-bass is 20 to 60 hertz. Bass is 60 to 250 hertz. Lower mid-range 250 to 2000 hertz. Higher mid-range 2000 to 4000 hertz. Presence range 4000 to 6000 hertz. And high-end or brilliance from 6000 to 20000 hertz. He also provides a chart with more specific categorization that looks like this. All of these frequencies are present on this graph. You may notice that they're not grouped particularly evenly, which is something I myself was curious about. As it turns out, these visualizers are designed to represent and accommodate human hearing, which is logarithmic rather than linear. So this is a rather complex topic, albeit a very interesting one. But if that's something you'd like me to cover in a separate video, let me know. Now each instrument has a range of frequencies within this spectrum that it's able to play. There is a fundamental frequency range for every instrument, including the human voice. And then there's the upper harmonics of those frequencies, which has to do with the overtone series. These are what make music sound more complex than just a basic sine wave. These upper harmonics affect the tone of the sound, or the timbre. I know, it doesn't look like it should be pronounced that way. This can sometimes be described as the tonal quality, or the color, or sometimes the texture. The timbre of an instrument is part of what makes A4 on the piano so different than A4 on the guitar. So all of that said, you can think of EQ as a tool to help you accentuate certain frequencies over others. This differs from instrument to instrument, and that itself is something that professionals study for years and years. Osinski says the four primary goals of equalization are as follows. One, to make a mix element sound clearer and more defined. Two, to create an aural depth of field by bringing mix elements in and out of focus. Three, to make the mix element, or mix, bigger and larger than life. And four, to make all of the elements of a mix fit together better by putting each one in its own predominant frequency range. Knowing how to use a tool like EQ is what can separate an amateur mixing engineer from a professional one. For comparison's sake, a piece of natural wood can be really beautiful on its own, but a carpenter will know exactly how to cut and sculpt that wood to make it functional and make its natural grain stand out. That's what sound engineers are doing with EQ. But in a more practical sense, EQ can also be used to compensate for imperfections in a room's acoustics, or in a live setting, to help prevent feedback through a microphone. There are different kinds of EQ, different methods of EQ, and different filters used in EQ. Now, I'm not a sound engineer, so I can't give you any tips on how to make acoustic guitar pop in your mix, but I will show you how EQ itself works. First, I'm going to explain the most basic EQ terminology, and I've even made some audio demonstrations to help you better understand. We'll start with the different types of EQ. A graphic EQ is a connected series of peaking EQs that are centered around industry standard frequencies. Parametric EQ is the one I'll be using to demonstrate today. It's more versatile in the sense that you can create your own parameters using cues, and manipulate the boosts or cuts to be wide or narrow. You can do this using these notches on your equalizer, called notch filters. These can be moved primarily up and down, or left and right on some equalizers. The curve created when you pull these notches is known as a Q, as in the letter Q. This is short for the quality of the frequency. Cues can be wide or narrow. As I'm sure you can imagine, the possibilities are endless on parametric EQ. Dynamic EQs are used to control more specific frequencies. This type of EQ is commonly used to DS vocals, or to control bleed on a drum track, or keep the kick drum and the bass from canceling each other out, or to reduce a particular problem frequency. Now, while these different types cater to different functions and workflows, they do all operate on the same idea, additive EQ and subtractive EQ. These, believe it or not, are quite literal. Additive EQ is the process of increasing or boosting certain frequencies. Subtractive is the process of decreasing or cutting certain frequencies. It's beneficial to play around with an equalizer at some point in your studies, even if you don't plan to do any mixing yourself. It really helps you understand the way musical sound functions. Additive and subtractive EQ will sound completely different with each instrument and even each audio file you record. This is a graphic equalizer. Notice the designated frequency bands at the top. Let's see what happens when I play around with Now, additive and subtractive EQ each have their place, but it's common for novice mixers to use additive EQ to highlight certain desirable frequencies. This isn't incorrect, but many will advise to use subtractive EQ to remove certain undesirable frequencies instead, in order to leave space for the sounds you actually want in your mix. Again, I'm not a mix engineer, so I'm not trying to give any advice in any capacity. This is just one of those ideas that's commonly known and debated in the world of recorded music. Of course, a proper mix is likely a combination of the two. But mixing is a lot like cooking in music. People mix to taste rather than based on any type of formula. Formulae don't work because of things like space, variations of the same instrument, mics and mic techniques, and more. So one can understand where an acoustic guitar sits sonically, but they're also mostly, if not completely, using their ear to determine what sounds good. Anyway, additive and subtractive EQ work vertically. There are a few common EQ curves that utilize additive and subtractive EQ in specific ways. Without getting too much into how to use them, I'll briefly explain what each of them is intended to do. There's shelving EQ, which boosts or cuts specific frequencies by the same amount. Tilt EQ is similar, but creates the opposite effect on the opposite end. It looks something like this. Peaking or bell EQ boosts or cuts around a central frequency. This one is shaped like a bell. And then there are four types of EQ filters that are commonly used in music. A filter is a more limited form of equalization that only cuts or rolls off the frequencies below an assigned frequency point. Filters are commonly used not only to clean up a mix, for example by removing unwanted background noise, but they're also used to create specific effects on the audio. You may recognize one or all of them. The first type of filter is a high-pass filter. This is a technique that removes low frequencies from the audio signal, allowing only the high frequencies to pass through. This is also commonly referred to as a low-cut filter. Then there's the low-pass filter, which, as you may have guessed, removes high frequencies from the audio signal, allowing only the low frequencies to pass through. This is also sometimes referred to as a high-cut filter. The third type is called a band-pass filter. This type of EQ allows for specific frequencies to pass through while cutting everything else. You could also sort of think of it as a low-cut and a high-cut filter used at the same time. A fun effect that can be applied using filters is called a filter sweep. I think many of you will recognize this in many different genres of music, even if you didn't know what it was called. There are different kinds of filter sweeps, but the basic idea is that the EQ is set to modulate between different frequencies. This means that the filter sweeps across a range of frequencies to create different tonal qualities throughout your piece, for example, from low to high. Possibly the most recognizable use of a filter sweep is what you hear when someone uses a wah pedal. But here are some other well-known songs that utilize filter sweeps. The quickest way to gain a fundamental understanding of EQ is to hear it for yourself, so let's do that together. I'll demonstrate how EQ can change the tonal quality of different instruments in a track. The way I do this will be very extreme compared to the way someone would actually use EQ in a mix. Keep in mind that everyone who's a mix engineer or a composer or a producer started somewhere. It's my hope that you understand and appreciate equalization a little more than you did when you clicked this video. If you feel overwhelmed by these concepts, take them slow. Watch part of this video, play around with your equalizer in GarageBand or something, and then just come back and watch this again. Things will start to make sense. I've also linked some online sources for people without access to a DAW, so check them out. There's even a Chrome extension for sound equalization. Thank you so much for watching. 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