Basic Guide to Understanding Audio Equalizers

This guide aims to give you a better understanding of the different types and uses of equalizers used in music production as well as offers some basic EQing tips to maximize your music.

Equalizers

During the course of a project, mixing and equalization are often one of the most important processes that can ultimately make or break your tune. Proper EQing is essential to add clarity and depth to your music, balance elements in a mix, and enhance sounds. Equalization is commonly used in music production to boost or cut specific frequency ranges to create depth and space in a mix, improve or emphasize the sound of particular elements, isolate or remove specific frequencies, and fix sounds with competing frequency ranges to achieve clarity. Equalization is critical for creating a polished track and a professional sound.

Equalizers Explained

There are multiple types of equalizers, but the most common equalizers in music production are parametric, graphic, and shelving equalizers.

Shelving Equalizer

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This type of equalizer is the most basic out of the three types and is commonly found in nearly all sound mixers and amplifiers. Shelving equalizers allow for cutting or boosting of the signal at fixed frequency ranges and often have predetermined filter curves. There are two different varieties: high-pass and low-pass. Low-pass shelving filters attenuate all frequencies above a specified cutoff frequency while retaining all the frequencies below the cutoff frequency. A high-pass filter does the opposite, by allowing all frequencies above the specified cutoff frequency to pass while attenuating everything below. The fixed frequency ranges for the low-shelf filter may begin to roll off around 150 Hz and below, while the high-shelf filter may begin to roll off around 10,000 Hz and above. Typically, shelving equalizers have ‘Low’ and ‘High’ knobs, and sometimes a ‘Mid’ knob for adjusting the midpoint frequencies. Analog shelving equalizers are great for adding color to your sounds in a musical way that enhances a sound. This is sometimes referred to as ‘sweetening.’

Graphic Equalizer

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Graphic equalizers give you the ability to adjust a range of frequencies using a bank of slider controls that are evenly spaced to boost or attenuate the signal through the audio spectrum from around 20 Hz up to 20,000 kHz. Basic graphic equalizers will have two or three bands, while more advanced graphic equalizers can have up to 30 or more bands. Graphic equalizers with narrower bandwidths have greater precision and are generally used to fine-tune the overall mix. They are not as effective when mixing because there is no control over the filter shape, steepness of the filter shape, and bandwidth of each individual band. Yes, more sliders provide more accuracy, but for optimum control, a parametric equalizer is recommended. When working with a graphic equalizer, it’s better to make small, incremental adjustments over a wider spectrum to round out your final mix rather than making drastic adjustments to any particular frequency bands.

Parametric Equalizer

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Parametric Equalizer

Parametric equalizers are the most common and flexible form of equalization. This multiband equalizer has fully configurable and adjustable frequency bands that can be individually enabled or disabled to cut, boost, and filter individual frequency ranges with the highest precision. Parametric equalizers are typically digital and offer the highest possible sound quality. This type of equalizer is often used to shape a sound precisely at each defined frequency and is recommended for doing any surgical work like cutting harsh or unpleasant frequencies.

Common parameters found on a parametric equalizer include:

  • Frequency: Adjusts the frequency range for each selected band.
  • Gain: Sets the level of the selected band. This parameter is often deactivated when the low-pass or high-pass filter shape is selected.
  • Resonance or ‘Q’: Controls the bandwidth by allowing you to widen or narrow the selected frequency band.
  • Filter Slope: Sets the steepness of the filter when either the low-pass or high-pass filter is selected.
  • Filter Type: Allows you to choose the filter shape for the selected frequency band.

Common Filter Types

Understanding the different filter types and knowing how they change the signal is also key knowledge when treating sounds. Below are some common filter types used to shape your sounds.

Low-pass: Removes frequencies above the selected frequency cutoff and passes everything below.

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Low Shelf: Passes all frequencies, but attenuates or boosts frequencies below the shelf frequency band by specified amount.

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Bell Curve: Attenuates or boosts frequencies over a determined range. Bell curves can be wide or narrow.

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Notch: Attenuates frequencies over a determined range allowing low and high frequencies to pass on either side of the cutoff. Also referred to as a band-rejection filter.

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Band-pass: Passes frequencies within a certain range and removes frequencies outside that range.

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High Shelf: Passes all frequencies, but attenuates or boosts frequencies above the shelf frequency band by specified amount.

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High-pass: Removes frequencies below the selected frequency cutoff and passes everything above.

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General EQ Tips and Techniques

To further explain equalization, we will use Ableton Live’s ‘EQ Eight’ device to show some basic EQing techniques and explore some common features found on most EQ plugins. These tips apply to any DAW program or parametric equalizer.

The goal when using an equalizer is to either boost, cut or attenuate certain audio frequencies of sounds to give them depth and space in a mix, emphasize certain characteristics of sounds so they cut through the mix better, isolate or remove specific frequencies, and reduce muddiness with competing frequency ranges to achieve clarity.

Cut Unwanted Frequencies

A great way to begin EQing sounds, so they sit better in the mix is to first remove any unnecessary frequencies using either a low-pass or high-pass filter. For example, high-hats usually sit higher in the frequency spectrum but may produce unnecessary low frequencies that can be removed using a high-pass filter. This approach will clean up the sound and help the high-hats cut through the mix better. Using a similar technique, you could use a low-pass filter to remove any unnecessary high frequencies from your bass, which will open up space and allow a lead sound that has higher frequency content to cut through the mix better.

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Subtractive EQ

Subtractive EQing is an equalization technique where you reduce frequencies instead of boosting them to allow a sound stand out better in the mix. Give subtractive EQing a try and you may find out that less is more. Often, many of us want to boost frequencies to emphasize certain characteristics of sounds so they cut through the mix. This is fine, but sometimes reducing frequencies is better than adding them. For example, say you have a high lead synth and a low lead synth playing together, and at the moment it’s hard to distinguish them apart. One option could be to boost the high frequencies of the high lead synth to make it stand out more. This would work, but there is also another option. Try instead adding a high-shelf filter to the low lead synth to cut away some high frequencies, which will make the high frequencies of the high lead synth seem brighter. The high lead synth will also retain a more natural and realistic sound compared to boosting it.

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In addition, if you tend to boost a lot of frequencies then the end result will leave you with a lot of competing frequencies, which will ultimately muddy up the mix or create a more sharp and thinner sound. Avoid the temptation to boost the same frequencies on every instrument or track as well because those frequencies will collectively overwhelm the mix and once again muddy things up. Using subtractive EQing will help give your mix added clarity and separation, allowing individual sounds to be heard clearly. This technique may be a bit more tedious, but the end result will leave you with a warmer, more natural mix.

Mixing in Context

A common mistake that can be hard to break, and what I still do at times, is to EQ instruments or tracks separately in isolation to make them sound as awesome as possible. Although this might make an instrument sound great while soloed, it may sound like rubbish once the other elements of the mix are brought into play. It’s recommended to make EQ moves in context of a mix because that’s where things need to sound good, right? It’s important to use the solo button sparingly and make your EQ adjustments while all your tracks are playing at the same time to get your sounds sitting in the mix properly.

Up Front or Back Seat

Equalization is also great for achieving depth. For example, boosting high frequencies bring sounds forward in the mix and makes them sound more present. Reducing high frequencies has the opposite effect and makes sounds seem further back in the mix and more distant. Boosting low frequencies has a different effect and can make sounds warmer or more full while reducing too many low frequencies can make a sound thin, shrill or less powerful.

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Sound Separation

When writing a tune, try to remember to give everything it’s own place in the mix. Try EQing every instrument with slightly different frequency ranges to give them separation so that they won’t clash with each other. As a whole, this will help your mix have clarity and sound full across the frequency spectrum.

However, giving instruments their own space in the mix can be accomplished with little or no EQing. Try instead, panning instruments to improve clarity. Having too many instruments in the same panning location can create conflicting frequencies as well. In addition, try using a plugin such as Ableton Live’s Utility device to widen or narrow the stereo width of an instrument to give the sound it’s own place in the mix.

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Fixing Unpleasant Frequencies

At times you may hear a sound with some unpleasant frequencies that you’re not sure how to eliminate. Well, one easy method to fix problem frequencies is to find the parts of a sound that need to be removed by using a parametric EQ. Try boosting the gain way up on one band with a narrow ‘Q’ and then using the frequency knob to ‘sweep’ across the frequency spectrum until the problem sound becomes prominent. The unpleasant elements should really stand out because the gain is so high. When you find the frequency where the problem is at it’s worst, reduce the gain to cut that frequency and adjust the ‘Q’ until you have happily removed the problem.

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Boost Wide and Cut Narrow

When EQing it’s more often better to make subtle moves to avoid diminishing a sound. When cutting frequencies, try to make narrow cuts by increasing the ‘Q’ instead of having wide cuts. Wider cuts will remove too many frequencies and ultimately make a sound dull or weak. When boosting frequencies, try using a wider ‘Q’ while increasing the ‘Gain’ slightly to achieve more natural results. Narrow boosts sound more harsh and unnatural. Also, you could run into problems with high spikes in the overall mix signal.

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It is also ok to use several equalizers in a chain to reach your desired results. In addition, using multiple equalizers will spread out the workload. You could even use different types of equalizers that each color the sound differently to achieve a more enhanced sound.

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Lend an Ear

Lend a helping ear to your buddy. Getting a second opinion on your mixing and EQing from someone that isn’t too close to the project helps tremendously.

Conclusion

Applying this basic knowledge to proper EQing is important for today’s music production process. It can be used to correct problems, improve sounds, allow elements to have their own space in the mix, or in a more creative manner, allow you to shape sounds in a less natural, but in a musically creative way. Use these tips as needed, but whatever you do, try not to get into the habit of thinking that radical amounts of EQing will help fix an imperfect sound during the mixing stage.

EQ Frequency Chart

Future Music has created a useful EQ frequency chart which should give you a rough idea about the frequency ranges for different sounds. Keep in mind that EQ moves will vary depending on the sounds you’re using and most importantly your ears!

Future Music

 


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