EQ Explained: All Things Are Not Equal

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Thanks to the development of low-cost, high-quality digital recording gear, the world is now populated by people who record their own music, yet have never touched a soundboard. While we applaud this healthy trend, there’s still plenty of old-school know-how that can enhance the recording experience. Not the least of which is an understanding of equalization. It can be your best friend or worst enemy while tracking and mixing music, and there are countless opinions about EQ. We’re going to touch on some fundamental truths about the topic to help you optimize your studio drum sounds.

Preparation

The best way to use EQ is sparingly, or even not at all. And to do so, you need to make sure your drums sound so damn good that you won’t have to touch a knob on the equalizer. Sure you can use equalization to hide an offending sound, but whenever you decide to “fix it in the mix,” you run the risk of diminishing the overall integrity of the recording. It’s best to solve your sound problems early in the process.

Always ask for suggestions. Before you start turning knobs, try new tunings, experiment with heads and change miking configurations. Also, if it’s not broken, don’t try to fix it. People who wouldn’t dare touch an equalizer if their lives depended on it have recorded some of the best drum sounds that I’ve ever heard.

Acoustical Principles

With that said, let’s talk about how equalizers affect the way our ears perceive sound waves that come from a pair of speakers. Let’s start at the beginning. When a stick hits a drumhead, the head is pushed down and in reaction pulls back up, like a spring. This fluctuation causes the air molecules immediately around the head to compress, then return to their normal pressure. The energy from these molecules is then passed on to the molecules around them causing a chain reaction.

The fluctuation of air pressure makes the drum shell and bottom head vibrate sympathetically, causing even more complex fluctuations of air pressure. This expanding of high and low pressure is called a sound wave, and the number of times that the pressure fluctuates from its maximum to minimum in one second is called the frequency.

Sound wave frequency is measured in Hertz (Hz) in honor of Heinrich Hertz, who made many contributions to the study of sound. One cycle per second = 1Hz. The vibrations of the drum cause many different sound waves, with a large variety of frequencies. For instance, the stick hitting the head creates the highest frequencies. And the resonation of the shell and bottom head creates the lower frequencies. An equalizer will allow you to raise or lower the amplitude (volume) at different frequency bands. So if you wanted to increase the attack of the drum, which would be the stick hitting the head, then you would use the equalizer to raise the amplitude of the higher frequencies.

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Fig. 1

Types of Equalizers

The three most common types of equalizers are parametric, graphic and shelving equalizers. Graphic equalizers have anywhere from three to 31 fixed frequencies that allow you to raise or lower the amplitude. They commonly span from around 20 Hz to 20 kHz (20,000 Hz), which represent the range that humans can hear sound with distinction. Drums often create frequencies above and below these limits, but our ears simply cannot detect them.

When you raise the volume on a graphic EQ at 1 kHz, you will also raise the frequencies around it at a fixed bandwidth set by the manufacturer. This affects the amplitude at frequencies from 300 Hz to 5 kHz (see Fig. 1). With a graphic equalizer you can apply many more cuts and boosts to a wide range of frequencies than you can with other equalizers. But the disadvantage is that you have to apply these at frequencies set by the manufacturer – you cannot adjust the bandwidth of the boost or cut.

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Fig. 2

Parametric equalizers allow you to choose both the exact frequency of the boost or cut and the bandwidth, which on most parametric EQs is called the “Q.” This means that you can sweep through all of the frequencies that the EQ allows, pinpointing exactly where you want to adjust the signal. The “Q” will then allow you to widen or narrow how far the boost or cut affects the other frequencies above and below it (see Fig. 2). Parametric equalizers allow you to be very picky about your adjustments, but only allow you to boost or cut at one or two points.

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Fig. 3

Shelving equalizers are the most simple, yet sometimes most flattering types of EQ. These equalizers allow you to raise or lower all frequencies above or below a certain point. Sometimes that point is fixed, like you find in most consoles where there is only a “high” or “low” control. And sometimes you can sweep up and down where the shelf starts (see Fig. 3). These equalizers sound very natural, and with one adjustment you can affect a much broader range of frequencies. But you have less control and the adjustment can be very drastic.

Drum Profiles

Now let’s talk about the acoustical characteristics of each part of the drum kit. The kick drum is responsible for the very low end of your drum sound. Therefore, it can require a good deal of attention. The very bottom end of the kick sits around 40-200 Hz. By boosting a few decibels in this area you feel the sound more than actually hear it, and it will give the drum a boomier characteristic. A good solid sounding low end is very important in most drum sounds, but be very careful when boosting too much in this area. Doing so will take up too much energy in your mix and consequently mask everything else. A lot of muddiness hangs out in the area from 200-900 Hz. You can clean and round out the kick by finding and cutting the muddiest frequency. But be careful – cut too much and you can suck the life out of the sound. The impact of the kick is heard in the 2-8 kHz range. Boosting this area will provide some top end and air to the sound, with more beater attack and click.

The snare tends to be the most characteristic sound of each drum kit and can require a good deal of attention to bring out its best qualities. The body and muddiness of most snares sit very close together, around 100-400 Hz. Finding and accentuating the body of the snare will provide a fatter sound. But too much low end can allow the kick drum to bleed into the snare sound, and you want to be careful not to bring out too much muddiness along with it. Some of the papery and honky characteristics of the snare sit around 200-800 Hz and can be cut or boosted to taste. The attack of the stick and the vibrations of the snares themselves range from 5-10 kHz. Boosting here can add clarity and presence to help the snare stand out in the mix.

Of course, toms vary in size, so each one will likely need a slightly different treatment. But for the most part the lows vary from 40-300 Hz. Many times toms vibrate with a low rumble while you hit the kick and snare, so boosting this area can fatten up the toms, but can also add rumbling while they aren’t being played. One way to help avoid this is to apply tissue or gel to the drum, but be careful not to choke it too much. Areas around 4000 Hz to 1 kHz tend to be boxy and can be cut to round the toms out. Much like the kick, areas around 3-8 kHz are the clicky and airy qualities and can help add attack and definition to the toms.

The cymbals provide the very high-end and clarity to the sound of your kit. Since the hi-hat and ride often keep the tempo, they can benefit by bringing out qualities with more presence. The cymbals usually don’t produce frequencies below 200-400 Hz, but bleed from the rest of the kit can occupy this area in the track. So by rolling off everything below that point, you can help the cymbals stand out a little more. But you can also take the life out of them, so be careful. Cymbals put out a lot of energy around 1-4 kHz that can be irritating or harsh and can be cut. The crisp qualities and clarity occupy areas around 6-9 kHz, while the sizzle and air hang out around 10-16 kHz. These areas can sometimes help the cymbals sound clear and present if boosted. But it is very important not to boost these areas too much, because they can cause “listener fatigue” and become annoying.

So on a broader spectrum, full or rumbly frequencies are around 40-200 Hz. Warm or muddy frequencies are around 200-800 Hz. Boxy or phone-like frequencies are around 800 Hz-3 kHz. Frequencies with attack and clicky qualities are around 3-8 kHz. And frequencies that are airy and sizzle are from 8-16 kHz.

Final Thoughts

The most important thing to remember is that there is no right or wrong way to equalize your drum tracks. There are only common rules that can help you understand how different frequencies produce different types of sounds. I always listen to all types of productions on the speakers that I mix on in order to hear how other people treat sound.

Another way to help you understand different frequencies is to use a parametric equalizer. Put the equalizer on a sound and raise the amplitude as high as you can with a narrow bandwidth. Then sweep up and down the spectrum to hear what the qualities of each frequency area are and how they affect the sound.

Whether you record and mix yourself, or work with another engineer, it is important to try new and different things and learn along the way. It will help you explore your tastes to find out what you like and dislike. These tastes will also most likely change as you progress in your understanding of equalization. So use your ears as your guide and continue to experiment with different ways to achieve the sounds that you love.