The EQ, short for equaliser, is the most important tool in any mixing engineer’s kit (aside from the level fader, of course). If you’re new to DAWs or mixers, you might be wondering what an EQ even is and how it’s used. And what’s the difference between a parametric and a graphic equaliser? In this blog, I’ll explain everything and even include explanations of important terms like curve and low cut/high pass.
- Equalisers in a Nutshell
- What’s an equaliser?
- Why It’s Important to Use an EQ
- Graphic EQs
- Parametric EQs
- Equalisers: An In-Depth Look
- Common Issues
- Vocals and Instruments
- Sound Synthesis
- Frequency Corrections
- Price Tags
- See Also
Equalisers in a Nutshell
What’s an Equaliser?
Have you ever used the bass or treble control on a sound system? It’s the same as a simple EQ, which is essentially the volume control for specific parts of the frequency range. The bass control is used for the lows, while the treble control sets the highs. Most people have probably used an equaliser before without even realising it, but what does equalising entail in practice?
Why Use Equalisers?
If you start working with multi-instrument recordings, you’ll notice that some instruments get pushed to the back of the mix and are barely audible. This phenomenon is called the masking effect, which generally happens when multiple instruments are playing in the same frequency range at the same time. Using an equaliser, instruments can be ‘separated’ by, for instance, removing any useless lower frequencies from vocals or guitar parts. By cleaning up some of this sonic clutter with a high-pass filter (more on this later), you create more room for the bass guitar or kick drum. Conversely, it’s also possible to boost specific frequencies to enhance vocal intelligibility or emphasize certain characteristics of an instrument. Equalisers come in all shapes and sizes and can be divided into two categories in terms of how they’re controlled: graphic and parametric equalisers.
Graphic EQs split the entire audible frequency spectrum into a number of bands. Each band is limited to fixed frequency range and has a slider that’s used to turn up or down its volume and that of any directly neighbouring bands. You might find more modest graphic EQs with seven or so bands in guitar and bass amplifiers and pedals. In concert rooms, the master output of the mixer is usually hooked up to a graphic EQ so the mix can be adjusted to the acoustics of the room. These professional models generally feature 31 bands, sometimes even separate sections for the left and right channel. The nice thing about graphic equalisers is that they offer a clear overview of the entire frequency range.
Parametric EQs usually have anywhere from three to seven bands. That may not look like much, but unlike with their graphic counterparts, the individual frequency bands are not fixed but can be user-customised via a ‘frequency’ control. In some cases, this means access to the entire spectrum, while in others, the bands partly overlap and leave you a little more limited. Using the Gain control, any selected frequency can be turned up or down, and the Q-factor determines to what extent the band affects its direct neighbours. Often used for live and studio mixing, parametric EQs can often be found in DAW software and on the individual channels of mixing desks.
Equalisers, mainly the parametric ones, offer various kinds of curves. In a graphic EQ, these are always ‘bell’-curves, used to cut or boost specific frequencies (see image 1 below). Low-cut filters, also referred to as high-pass filters, are then used to remove everything below the set frequency. The exact opposite is done using a high-cut (or low-pass) filter, which’ll take out anything above the set frequency threshold. Both types of filter can be seen in the second image below. Also, the treble and bass controls I brought up earlier are referred to here as the high and low shelves (see image 3). A low shelf allows you to gradually enhance or attenuate anything below the set frequency, while the high shelf lets you boost or cut anything above it.
Image 1 – Left: Bell Boost with Low Q-Factor / Right: Bell Cut with High Q-Factor:
Image 2 – Left: High-Pass/Low-Cut filter / Right: Low-Pass/High-Cut Filter:
Image 3: Left: Low Shelf Cut and Boost / Right: High Shelf Cut and Boost:
Equalisers – The Full Break-Down
So, equalisers allow you to adjust the colour of audio signals by cutting or boosting specific frequencies; a creative and above all personal process that every producer completes as they see fit. On one hand, you’re free to make tracks sound the way you think they should sound, but on the other hand, there’s something called experience. In movie-quote words: “I want to see a negative before I provide you with a positive.” (Blade Runner). What I’m trying to say is that it’s important to learn how not to do things before you learn how things should be done. After all, decision making is crucial when you’re equalising audio.
Sound-inflation is one of the pitfalls that comes with equalisation. After a while, especially if you’ve done a lot of tweaking, you’ll start struggling to hear more nuanced changes.
The only solution is frequent A/B’ing: listening to existing tracks that belong to the same genre as your mix while you’re slaving away at it. This way, your hearing is reset since your ears are suddenly exposed to something that sounds ‘fresh’. Also, listening to tunes in a completely different genre certainly won’t do any harm either.
Another pitfall is the risk of high-end frequencies getting increasingly louder across the board. Unsuspectingly, you boost one instrument using your EQ before the next, and the next, and the next, until finally you’ve given so many instruments a little extra presence you can no longer hear that first, second and third instrument that you boosted. Again, the golden rule includes A/B’ing and checking out what other producers have done to counter this issue. In any case, mixing means making choices, and sometimes you’ve simply no choice but to push the most beautiful-sounding instruments a little more towards the background to make way for others in the foreground. In the famous words of William Faulkner: you’ve got to “kill your darlings.”
Vocals and Instruments
When working with vocals, you can boost the high frequencies (trebles) to improve word articulation. At the same time, this adds a little extra sparkle to the vocals, resulting in the kind of lush sound that’s often dropped in pop music.
Someone who’s turned ‘playing with’ the higher frequencies into an art form, at least when it comes to her pop-style vocals (chest voice), is soprano Sarah Brightman. Since Brightman sings in a soft voice that already gives her vocals an airy sound, injecting a serious amount of trebles above the 12,000Hz mark while curbing the lows and mids results in a sound that’s almost like melodic whispering.
Needless to say, tenor, baritone and bass singers benefit from a high-end boost for the same reasons that sopranos like Brightman do: clear sound and improved articulation. However, since our ‘normal,’ every-day voices aren’t exactly put through an EQ before use, you might be wondering why it’s important to ‘refine’ vocals in the first place. The answer is the mix. So they can be clearly heard, vocals need to almost literally sit on top of any instruments. These days, instruments and even complete orchestras are often recorded close-miked and, just like vocals, they’re polished up with an equaliser to flesh out the sound. The time of simply pushing vocals to the foreground while hushing up the orchestra in the back is long gone, meaning that in today’s full-range mixes vocals demand and deserve some touching up.
Back in the day of Wagner’s theatrical operas, none of the above applied. Electronic amplifiers weren’t a thing yet, never mind electronic equalisers. Since the chest-voice isn’t powerful enough to rise out above a large instrumental backing ensemble, soprano and tenor vocalists sang falsetto, which is louder as well as clearer. With that in mind, it’s safe to say that Sarah Brightman’s airy, chest-voice pop vocals are typically used for studio acts, simply because it’s virtually impossible to achieve a similar sound when playing unplugged. It can be pulled off on stage, but only if you’ve got amplification (and an EQ), plus an engineer who knows what they’re doing.
Getting vocals to stand out while maintaining the right sound for every part of the mix is what mixing is about nowadays. Just remember that you’re free to push back one instrument by scraping away a bit of high-end while giving more sonic prominence to another. This is where your style and personal preferences come in.
Check out a musical film and you’ll notice that the conversational speech of each performer has a different sound than their vocals. Since the songs are separate studio recordings that have been mixed in with the sound of the film, the vocals in the music obviously sound brighter and clearer than the spoken dialogue. Technically, this discrepancy makes for incorrect sound, and it’d be more authentic to brush up the studio version with an equaliser to match the sung sections with the spoken sections.
In a lot of films, things are even more extreme thanks to the frequent use of overdubs (pre-recorded monologue/dialogue), which sound more crisp and don’t include any ambient noise. Next time you’re watching a movie that includes a speaking character riding a horse into the distance, remember that the film crew is far away from them and that there can’t possibly be a boom arm suspended above the horse. In other words, whatever the character is saying is an overdub. That said, wouldn’t it be great if post-editing included equalisation so overdubs start sounding a little more like normal dialogue?
Since it’s the stretch that includes the bass, there’s countless ways you can butcher the mid-low frequency range. Too much reverb or delay can be devastating, so you have to maintain full focus when mixing any mid-lows. It normally doesn’t hurt to reign these frequencies in just a little. What’s more, this will give you more breathing room in the mix, but that doesn’t mean you’re not supposed to have any mid-lows in there at all. For some calm and composure, just give the bass some space without overpowering any of the other instruments.
Take Thriller by Michael Jackson. The iconic bass lines sound fairly dry and isolated, and even the kick drum hasn’t been given any extreme prominence across the low-end. At the same time, the kick does boast serious high-end presence, meaning there’s definitely a notion of a bass drum here and the low frequencies still have plenty of room to shine in the mid-low range – masterclass EQ’ing courtesy of Bruce Swedien.
Equalisers can also be used to alter the foundation sound of instruments such as electric guitars. Guitars in particular can benefit greatly from a few EQ-based touch-ups, since equalised tone running through, say, an overdrive stompbox gives you a different wet signal than what you’d get without the EQ. By removing a few highs, overdrive effects are reigned in and will eat up less space in the main mix – something that usually makes a big difference. Basically, since the wide stereo image of more frequency-hogging instruments takes up so much of the main mix, mixing in these kinds of situations is all about the art of omission.
That said, clean guitar signals are also fun to experiment with, and permanently deleting some of the highs produced by pianos can easily lend their sound more mix-cutting potential.
When it comes to synthesizers, equalizers have a special role. Technically, due to the way synthesis algorithms work, they’re fairly comparable to the filters loaded into synths. A filter marks a frequency above and/or below which all frequencies are bluntly removed. However, an equalizer marks a frequency range that can be made louder or softer, so the influence is mainly more subtle than that of a filter. Contemporary synthesizers in both hardware and software form (larger workstations especially), are often equipped with an equalizer as part of the effects section. The equaliser section of the FM8 (part of Komplete) is so readily available that the equalizer plays a core role in generating/colouring sounds. And indeed; you could spend hours shaping the perfect sound with oscillators and filters, but you can easily and quickly set the right tone with an equaliser.
All in all, if your hardware synthesizer doesn’t have an equaliser on board and if you can live with the fact that any EQ settings can’t be saved to your synthesizer, a stand-alone EQ can be a very interesting addition to a synthesizer from a sound-engineering point of view.
Click here for a complete overview of our Equaliser and Tone pedals
The best studio monitors and microphones have a flat frequency response, but do such monitors actually even exist? While the answer’s yes, the chances of you bumping into one are slim. Some professional recording studios use large PMC speakers, which are not only extremely flat in terms of frequency response but extremely expensive – we’re talking amounts that could buy you a house!
With a somewhat cheaper speaker, which won’t be as flat, you can still ‘fake’ a flatter frequency response. To do so, you’ll need an EQ and the right knowledge to correct, as it were, the somewhat wobbly frequency that’s characteristic of your speakers. Basically, this correction process is the main reason equalizers are made. Anyway, the best solution is of course always to use a speaker with a flatter frequency response, but these are simply more expensive and most likely not a feasible solution for everyone. The same can be said of microphones. Most decent microphone preamps are equipped with tone controls via which the sound character of a microphone can be tweaked.
Equalisers do not have to be particularly expensive, but of course there are also equalizers with the same price as a used mid-size car. The SPL Passeq is a good example. ‘Why so expensive’ you wonder. It is a bit of a complex story, and that story will certainly not appear in its completeness in this blog. But in a nutshell: the secret of expensive equalizers lies in the phase of the signal. This remains more accurate compared to the cheaper models where phase shifts are involved. It doesn’t seem very important, but large studios can afford it, and therefore employ engineers who do find the difference important.
If you know your EQ like the back of your hand, please share your best tips with us in the comments below!