What are all the different types of EQs, and when do you use them? Do you go with broad or surgical? Graphic or parametric? Dynamic or static? Read our beginners guide to navigate the right choice for any situation.
By Charles Hoffman
Equalization is the process of adjusting the balance of frequency components within an electrical signal, and the device used to apply equalization is called an equalizer, (EQ) which works by boosting or cutting the energy of frequency ranges known as bands.
An EQ that you’re likely familiar with is the one in your car that allows you to boost/cut bass and treble frequencies, though these EQs have relatively limited capabilities. The primary function of an EQ is to adjust the frequency response of audio captured by microphones and instrument pickups, as well as any electronic sounds.
EQs are generally simple to operate and can have a profound effect on the quality of a mix. They allow you to balance different elements of your song together and generate clarity within your mix. Think of it like puzzle pieces you’re trying to fit together; setting levels and EQing are crucial in achieving this. EQs also play a significant role in live sound, allowing engineers to compensate for the acoustics of the room their equipment is set up in, and “tune” the frequency response of the speakers.
There are various types of EQs, and choosing the right one for the situation is quite straightforward once you know what options are available, and how each functions.
A graphic equalizer sends incoming audio to a bank of filters that pass audio based on their assigned band, and a slide control is used to boost/cut the energy passed by each band. This type of EQ gets its name due to the way the slide controls resemble a graph representing the EQ’s response (Y) over frequency (X).
The number of filters used will dictate the type of graphic EQ you’re using. For example, an EQ that has the center frequency of its filters spaced one-third of an octave apart, with three filters to an octave is called a 1/3 octave equalizer. Following the same naming convention, an EQ with half as many filters per octave is called a 2/3 octave equalizer. The more filters there are per octave, the more control you’ll have over the response of the EQ.
The Waves GEQ Graphic Equalizer is a prime example of a graphic EQ intended for live sound. The design of this EQ is inspired by the DN series 1/3 octave equalizers that narrow filter width as a band’s gain increases. It also uses flat-top filters that remove artifacts that would otherwise result from band interaction.
Graphic EQs are particularly well suited to live sound situations, where the engineer can make rapid decisions with clearly marked sliders, without having to worry about fine-tuning each frequency band. This approach can also be taken in a mix where broader tonal strokes are desired. The API 560 is another great graphic EQ which can be used for this purpose.
A parametric EQ is a multi-band variable equalizer that allows you to control each band’s amplitude, center frequency and bandwidth. You’re able to boost/cut amplitude, shift center frequency up and down the frequency spectrum, and widen/narrow each band’s bandwidth. For the most part, parametric EQs find themselves at home in recording/mixing studios due to the precise adjustments they allow for.
The Waves H-EQ Hybrid Equalizer is a parametric EQ that features vintage and modern EQ curves, inspired by various British and American consoles. It allows you to choose between 7 different filter types for each band and enables a mid/side mode. Also included is a keyboard graphic that lets you match a band’s center frequency to a note on a keyboard. This EQ features a real-time frequency spectrum analyzer, a unique asymmetrical bell filter, a solo function for each band, and H-EQ Lite for live sound applications and CPU-taxing DAW sessions. This EQ allows you to fine-tune tonal decisions, and surgically remove problematic areas.
A static EQ boosts/cuts the energy of a band by a set amount, regardless of the level of the incoming audio signal. It doesn’t rely on a threshold level to boost/attenuate the gain of a band in the way that a dynamic EQ does. Most basic EQs are static by nature, and the primary stock EQ that’s part of your DAW is likely static as well.
An example of a situation in which you may use a static EQ is when setting up the sound system at a club. Let’s say the position of the venue’s speakers and the shape of the room have created a situation in which the bass response on the dance floor drops an outrageous 9dB; this can occur due to room modes. Acoustically treating the club by yourself likely isn’t an option, so your next best bet is to compensate for this issue using a static EQ to boost the low end of your sound system 9dB. This may cause problems in other parts of the club, but the primary listening environment (the dance floor) will now be taken care of.
You may choose to use a static EQ like the RS56 Passive EQ when fitting various elements together in a mix. Even if all the parts of your mix sound great on their own, you may experience frequency overlap that causes exaggerated transients, or masking of particular elements.
An example of when you may choose to use a static EQ to clear up your mix is when mixing your kick and snare together. It’s not uncommon for the top end of a kick to mask a snare in the 1-3kHz range, but using a dynamic solution like sidechain compression is not always the answer. By attenuating your kick to make room for the snare using sidechain compression, the kick will sound different each time the snare hits; this may not be the desired effect. By applying a static EQ, you can carve out space from your kick for the snare to live in, the effect of which persists between snare hits.
A dynamic EQ responds to an incoming audio signal using a threshold-based design. This sounds pretty similar to a compressor, right? At a glance, they are quite similar to one another, but the difference lies in how they process incoming audio.
A typical multiband compressor’s crossovers cause a phase shift. This means that if you use a multiband compressor for parallel compression, you could end up with certain crossovers that are out of phase with the dry track. Even if you aren’t performing parallel compression, this phase shift will create a change in your audio signal, even without compressing the incoming signal.
On the other hand, a dynamic EQ like the F6 Floating-Band Dynamic EQ doesn’t cause a phase shift until the input signal triggers the device. This means that they’re generally much more transparent than multiband compressors.
Dynamic EQs are often more attuned for surgical processing than multiband compressors, which are suited to processing broad frequency bands. For example, notching resonant frequencies out of a vocal is something that you may want to use a dynamic EQ for, because of the EQ’s particular ability with narrow frequency bands.
Multiband compressors like C6 still have their place and are quite desirable when performing buss compression. They tend to color the sound much more than dynamic EQs, and the lack of surgical precision they offer is what makes them sound musical.
Although dynamic EQs are capable of causing a phase shift, they’re often used in such a way that the phase shift is inaudible. Referring back the previous example in which a dynamic EQ is used to attenuate a resonant vocal, the notch that you would apply to do this would be so narrow, and react so quickly, that the phase shift caused would likely be inaudible. Keep in mind that your audio will be left relatively unaffected when the resonant frequencies aren’t present if you use a dynamic EQ.
A surgical EQ allows you to apply boosts/cuts to very narrow bands.
The ability to control the center frequency of each band in a parametric EQ makes them ideal for frequency fishing. The Q10 Equalizer contains 10 bands that you can apply surgical EQ boosts and cuts with. I haven’t come across a surgical graphic EQ before, and for good reason; being unable to change the center frequency of a band would make for quite a poor surgical EQ.
A technique known as frequency fishing exists that allows you to pinpoint resonant frequencies and then make the decision to attenuate them. To do this, narrow the bandwidth of one of your parametric EQ’s bands. Heavily boost the frequency of the band, and then slowly sweep it throughout the frequency range in which you’re trying to target a resonant frequency. As soon as the signal coming out of your speakers becomes extremely harsh, attenuate the level of the band until you’ve successfully dealt with the problematic frequency. This is how you could deal with an overly-resonant vocal like the one mentioned in the previous section. Additionally, this would be a good time to implement a dynamic EQ.
A mid-side EQ like the Scheps 73 allows you to affect the frequencies in the middle of your stereo image independent of frequencies on the sides of your stereo image, and vice versa. A device like this is particularly useful for carving space into a busy stereo mix.
In particular, mid-side EQs are great for mixing your busses together. Let’s assume you’re trying to mix a drum bus with a guitar bus that both have elements spread across your stereo field. Perhaps your hi-hats are getting lost behind two rhythm guitars panned out to the sides of your stereo image. By applying an EQ in “side mode” to your guitar buss and cutting away some of the frequency content that’s masking your hi-hats, it could be just enough to let your hi-hats through. The upside of using a mid-side EQ in this situation is that the middle of your stereo image is left unaffected, leaving your center-panned lead guitar untouched.
Minimum Phase EQs
Minimum phase EQs tend to cause a phase shift at their crossover points, similar to how multiband compressors produce a phase shift. This phase shift is a result of latency created by a band’s change in amplitude when it’s boosted/cut. In the analog world, companies that produce minimum phase EQs do what they can to minimize the effects of phase shifting, hence the name. In some situations, the phase shift that an EQ causes may be desirable.
In the digital world, analog emulations are ever prevalent, meaning nuances such as latency caused by adjusting band amplitudes are baked into plugins. There is a way around this since you can program the EQ from the ground up, but then it wouldn’t be true to its analog counterpart. To simplify things, minimum phase EQs are more likely to impart some type of color on your sound than linear phase EQs.
Linear Phase EQs
Linear phase EQs like Waves Linear Phase EQ are purely digital and are able to achieve zero phase shift when boosting/cutting bands. They’re able to manipulate the harmonic structure of an input signal without substantially affecting the overall output level of your audio signal. Due to this phenomenon, linear EQs are very desirable for mastering purposes and tend to color your sound less than minimum phase EQs.
This isn’t to say that you have to use a linear phase EQ for mastering purposes. If you like what a minimum phase EQ does to your mix, then use it. It’s good to have a basic understanding of the differences between minimum phase EQs and linear phase EQs because it may help you to make more well-informed decisions when processing your audio. At the end of the day, if your song sounds subjectively good and is formatted appropriately for distribution, anything is fair game.
There are many different types of EQs, each with their strengths and weaknesses. Choosing the right EQ is a matter of identifying your needs, selecting the EQ that makes the most sense for the task at hand, and then trying it out. If the EQ you’ve chosen at first is incapable of accomplishing what you had in mind, try another one. This process of trial and error could lead you down a path of discovery that spawns even more desirable results than you had initially anticipated.
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