EQ Basics: How, When, & Why to Use an Equalizer (BGAE Ep.3)
The Equalizer, otherwise known as the EQ, is probably the most used tool in audio. Originally created to enhance the tonal quality of telecommunications and radio transmission. The Equalizer began to show up in almost every audio appliance from home radios, to car stereos, to HiFi systems, to Ipods and cellphones. Now, in today's world our wireless headphones have apps to change the EQ levels,,, wild stuff.
If I were to say the ‘telephone’ effect, I'm sure you already have the sound in your head. The lack of bass in the voice, almost like a megaphone sound. Early day radio and telecommunications had bandwidth limits that prevented the full auditory spectrum from being transmitted. In fact, the full transmittable spectrum was 300Hz to 3.4KHz. This chopped all of the low end off, as well as the high end. Simply because the technology couldn’t yet transmit the full bandwidth of 20Hz to 20KHz.
The EQ was created to allow the broadcasting engineers to try and compensate for the lack of frequency bandwidth pre-transmission. Attempting to compensate for the lack of everything below 300Hz and everything above 3.4KHz, they would ‘smiley face’ the EQ, or add a lot of bass and a lot of highs.
Pre-Transmission full bandwidth Smiley Face EQ
Post-Transmission / What the listener hears out of their radio.
Now mind you, the first EQ ever made for broadcast and telecom was the Western Electric 7A Equalizer, made in the 1920’s. They didn't have the digital EQ’s used in the pictures above. Nonetheless the images of the spectrum remain accurate depiction of what was going on with the audio
1921 - Western Electric 7A Equalizer
The Graphic EQ -
Jumping to 1969 we get our first Graphic equalizer. The UREI 529, I’m breaking a historic timeline for the sake of linear learning here, so for the history buffs, there are a few EQ’s that came before this one that I'm passing over.
As you can see in the image above the UREI 529 provided set frequency bands. You could either turn those bands up, or down. You don't have the ability to move between the frequencies. This is the primary characteristic of a graphic equalizer, fixed frequency bands. If your graphic EQ has a 200hz band and a 300hz band, there is no way for you to move to 250hz due to the graphic EQ having fixed bands. The width of the bands is set as well. Each band also has a set Q-factor or quality factor.
Where a High Q factor means the band will have a narrow bandwidth.
A low Q factor means the band will have a wider bandwidth.
Graphic EQs have both Fixed bands and Fixed Q-factors! Each Graphic EQ is different too making each one unique in its own right.
The Semi-Parametric EQ -
A few years later in 1971, the API 550-A was released. The API 550-A is considered the first semi-parametric EQ. It's not quite a graphic EQ because each band, Low, Mid, and High. Have selectable frequencies. Meaning you’re not stuck with a single frequency for each band
-
The Blue lettering marks the frequency
-
The White lettering marks the gain adjustment in dB both + and -.
This makes the EQ fairly ‘tunable’ having limited movement within the between frequencies. Even though you’re still only given a few frequencies per band, you still have the ability to move left or right unlike the strict designation of the graphical EQ.
The API 550A has a proportional Q design, also called variable Q. This means the more you boost or cut, the more narrow the Q-factor gets.
Low gain Boost = low/ wide Q-factor
High gain Boost = High/ narrow Q-factor
The Parametric EQ -
In 1982 one of the most infamis fully parametric EQ’s arrived on the scene. The GML 8200, named after its creator, George Massenburg Labs.
A fully parametric EQ provides an infinite amount of control. Each band has a ‘sweepable’ frequency selection meaning the low band can sweep any frequency from 20Hz to 800Hz, your mid band can sweep from 400Hz to 6Khz, and your high band can sweep from 2Khz to 20Khz. If you want to adjust your EQ to precisely 120.5Hz, you can do that with a fully parametric EQ. Even more so with today's digital EQ’s and plugins and being able to simply type in a number.
Parametric EQs have fully adjustable Q-factors, fully adjustable frequencies, and fully adjustable boost/cut abilities. Your low band can overlap with your mid range band, and your mid band can overlap with your high range band.
Parametric EQs have the most control over your audio’s tonality.
(Image for illustrative purposes only, EQs that look like this are normally destructive)
So now that we know some history on why the EQ came about, and what the different types are and the different terminologies that go with them. Let’s get into How, When, and Why to use them in a musical way.
Removing unwanted frequencies -
One of the big reasons why the EQ comes out is because there is a frequency that sounds pretty bad. Either bad or more apparent than one desires. The EQ is like a volume knob for specific frequencies.
For example: Below we can see a very large spike around 365Hz, where the rest of the sound’s frequencies are pretty evenly spread out. This would make that 365Hz bump very apparent to our ears.
We can utilize an EQ to equalize the frequency to make it sound more even. Using a parametric EQ, We’ll reduce the gain at 365Hz until the frequency is smoothed out or less abrasive. We also want to make sure that we don't use too low/ wide of a Q-factor in order to target the specific frequency we are after. Otherwise if we use too wide of a Q-factor we could drag some of the surrounding frequencies down with it. So in this case, we use a parametric EQ with a high/ narrow Q-factor to target specifically 365Hz to reduce the gain of the frequency spike.
Use your ears for this not your eyes, using your eyes to mix is auditorily dangerous, you hear with your ears not with your eyes.
In the same boat but in the opposite direction, let's say your sound is lacking some low end.
You could use an EQ to boost the bass, or really any other frequency you feel you need more of. You may also notice that this EQ curve looks a little different than the others we’ve used so far. Don’t worry we’ll get into the different curve types in a few.
Adjusting tonality -
When we use an EQ, it changes the overall frequency content of the sound we’ve applied it to. This is also referred to as tonal balance. More often than not this is speaking within the context of your mix. Mixing is about blending different sounds together to make them all sound cohesive. The lack of cohesion could be caused by many things, but one thing that can help is using an EQ to help smooth out or shape the sounds to fit well with each other in a tonal sense.
Here are a few images that can help you reference different areas of tonality with their ‘technical’ names. I say ‘technical’ in quotes because though they may sound goofy, you’ll come across a wide variety of descriptive terms to describe how a sound sounds.
Woofy
Boxy
Nasally
Sharp
Brittle / Shrilly
If you come across a sound that fits any of these odd sounding terms, you can immediately use an eq to address the rough area to try and mitigate the issue. While some frequencies might stick out like a sore thumb, changing the tonal balance may include a low/ wider Q-factor to cover larger areas of the sound to be adjusted together as opposed to a single frequency with a high/ narrow Q-factor.
Creating Sonic Space
Think of the frequency spectrum as a sonic palette. In our Spectrum analyzer lesson we discussed decades and how low mid and high are separated into 3 different areas (this can be broken down more but we’ll keep it simple for now)
We have sounds like kick drum, bass guitars, subs, and floor toms that take up the lower decade around 100Hz and down. We have rhythm guitars, synths, pianos, vocals, and many other instruments that take up the middle decade from 100Hz to 1KHz. We also have cymbals, hi-hats, whistling, guitar solos, and other higher frequency sounds that take up the top decade from 1KHz to 10Khz with up to 20Khz being included in the higher decade.
This is not a dead set. In fact, a kick drums can take up 20Hz-10KHz, vocals can take up 100Hz-15KHz, a piano can be 40-20KHz taking up the entire sonic palette. This is another prime example of where the EQ comes into play.
Examples -
Kick Drum
This kick drum takes up 20Hz-20KHz
Purple Dot = Removing woof while adding punch
Red Dot = Removing Boxy sound
Green Dot = Removing sharpness and creating a smooth tone that leaves room for the other sounds
Blue Dot = turning down everything over 1KHz to make sonic space for the instruments that live up there.
Bass Guitar
As you can see below, this Bass Guitar takes up 20-20Khz, but we only need the low stuff so we can actually just get rid of all the high end information that's just taking up sonic space.
Blue Dot = Getting rid of what the speakers cant even reproduce
Green Dot = getting rid of everything over 200Hz because we just dont need it in our mix
Rhodes Piano
This Rhodes piano has too much low information. We need to get rid of some of it because it overlaps with our kick drum and our bass guitar and makes them both sound really bad when they all play together. So to allow the kick drum and bass guitar to have their own sonic space within the palette, we can strip the Rhodes of its low end information to free up some space. While we’re at it, the Rhodes sound is kind of dark even after the removal of the lows, so let's add some high end information to give it a brighter tone.
Green Dot = Cutting the bass out to give space to the Kick and Bass guitar
Blue Dot = boosting the high end information to make the Rhodes sound a little brighter
Snare Drum
Our snare drum also has more low end than we’d expected, it also sounds kind of weak and not very punchy. Let's take out the low end and add some punch to it. We can use the ‘Boxy” area to create a more punch snare sound around 100-200Hz. The snare also has a harsh high end that sounds kind of sharp. Let's ease into the harshness without taking away too much of the pop/ snap.
Green Dot = removal of unnecessary bass and addition of some punch around 150Hz
Blue Dot = removal of harshness without taking away too much of the brightness and pop
Shakers and hi-hats
Even though we cant hear the low frequency information, our spectrum analyzer shows us that there is in fact low frequency information happening in our shaker recording.
Since the shakers and hi-hats are high frequency instruments we can get rid of almost all the low and low mid information. This prevents sounds we really cant hear from interfering with our kick, bass guitar, our snare, AND our Rhodes piano. Just because we can't hear it doesn't mean it's not affecting the audio somehow.
Green Dot = Removal of the low frequency info to make sonic space for the rest of our instruments
A big point I want you to take away from these examples, is the fact that I had a reason behind each adjustment. I didn't just add an EQ because I think I should. I added the EQ to either enhance a quality I wanted more of, or mitigate an issue with overlapping sounds. Watching the video below will also really help you understand the audible conflicts that promote the use of an EQ.
The primary goal is to select sounds/ record sounds that are so good, and fit so well together, you don't actually need to use EQs. Though that's almost a perfect world, you can get really close to it. Had I selected shakers and hats that didn't have low end information I could have gotten away with not even EQing them.
Less is more in every aspect.
Before we end this lesson i want to cover the different EQ shapes / styles
The Bell -
The most common style of EQ shape is the bell. I think its obvious how it gets its name, it looks like a bell! These are good for adding or removing frequencies as well as shaping tone.
On the left hand side (Green Dot) we have a wide/ low-Q bell boost
On the right hand side (Blue Dot) we have a narrow/ high-Q bell cut
The Shelf -
The Shelf is used more to boost or cut the lows or highs as more of a group or region. On the left we have a low shelf that is boosting and on the right we have a high shelf that is cutting.
If we adjust the Q-factor of the shelf we can get some pretty interesting results
On the left we have a low shelf with a low-Q, and on the right we have high shelf with a high-Q. Having a high-Q on a shelf adds a frequency boost right before you cut OR it adds a cut right before you boost
On the left we have a low shelf high-Q boost and on the right we have a high shelf low-Q cut
Low Cut / High Cut - High Pass / Low Pass
A low cut is the same thing as a high pass
A low pass is the same this as a high cut
It’s simply a matter of perspective / whichever you prefer to think about it.
On the left we have a low cut, cutting out all the lows. In other words it's allowing all the highs to pass through
On the right we have a high cut, cutting out all the highs. In other words it’s allowing all the lows to pass through
Almost identically to the shelf, A low-Q will be a more gentle slope. While a high-Q will create a resonant peak right before it cuts everything out. The difference between a Shelf and a low cut/ high cut. Is that a shelf simply lowers the gain of the signal. A low cut / high cut actually gets rid of all the information instead of just turning it up or down.
The Notch filter -
The notch is like taking a chunk of the signal out. If you come across a sound that you like but it has a simply unbearable frequency in it. You can notch it out. I personally haven't used the notch very much because t does create a tonal absence in a sound, but i still recommend you mess around with it to understand the unique sound it has.
On the left we have a notch with a high-Q on the right we have a notch with a low-Q. It's also important to mention that a notch is only the removal of frequency content.
The Band Pass -
The band pass is fairly similar to having a low cut and a high cut, but instead, it's centered around a single point. It's also similar to a reversed notch filter, instead of removing a specific frequency, it's more focused on a specific area. Also if you remember from the beginning of this lesson it also looks like the telephone effect.
Band pass with a low-Q
Band pass with a high-Q
The Tilt Shelf -
The Tilt Shelf if kind of like having 2 shelfs of opposite directions connected to each other. If you boost the gain you’ll get more highs and cut the lows. Vice a versa if you cut the gain you'll lower the highs and boost the lows
Tilt Shelf with a low-Q with positive gain
Tilt Shelf with High-Q and negative gain
The Flat Tilt -
Lastly we have the Flat Tilt, just like the Shift tilt but without the ability to adjust the Q-factor. If we add positive gain/ boost, we get more highs. If we attenuate or cut, we get more lows.
Positive gain / Boosted
Negative gain/ attenuation / cut
As you can now understand, the EQ is a very powerful tool. It allows us to create space in our mix, it allows us to shape the tonality of our selected/ recorded sounds. While originally designed for radio broadcasting, it revolutionized the recording industry allowing us to bled sonics like never before.
A EQ can be used in an impractical creative way, or in a practical logical way. The choices are endless. The EQ can both help us create a more cohesive mix, or absolutely destroy our sound if not used with intention and care.
Remember, only use it if you have a justifiable reason to. The goal is to not have to use it. Always make adjustments with your ears and not your eyes and don't forget to gain stage after you make your adjustments.
If your audio was at -6dB before you added an EQ, make sure its still at -6dB when you're done using the EQ by adjusting the output gain knob.
I’ll catch you next week where we’ll get into compressors !