Content provided by: Bobby Owsinski
The following excerpt from "The Mixing Engineer's Handbook" by engineer Bobby Owsinski discusses how EQ can affect different frequencies in an audio mix. A Tips and Tricks section at the the end features various professional engineers offering their perspective on EQ techniques.
Before we examine some methods of equalizing, it’s important to note the areas of the audio band and what effect they have on what we hear. The audio band can effectively be broken down into seven distinct ranges, each one having enormous impact on the total sound.
• Sub-Bass — The first usable octave for most recording is the 40 - 80 Hz range, with equalization settings centered around 50 Hz. This range of frequencies is often referred to as "Low Bass" There is sound between 20 Hz and 40 Hz but little or no sound from instruments. The lowest pipes of a pipe organ will get into this range but more "ordinary" instruments like Bass Guitar, Upright Bass and Foot Drums do not. The lowest pitch on a bass guitar or string bass is at 41 Hz. Thunder, earthquakes and rumble from the building shaking extend below 40 Hz. While mixing, watch out for objectionable sounds below 40 Hz caused by building shifts and mic stands moving with heavy footsteps. If there are objectionable sounds in this range, the range can usually be taken entirely out with a filter. The first octave that we deal with (40 - 80Hz) gives more of a "feeling" and sense of "power" to the sound. This range is way down or non-existent in smaller stereo systems. This range is difficult to hear at all at medium and low volume levels because of the Fletcher-Munson Effect. To properly set the amount of low bass in your mix or in your instrument sound, you must listen both loud and soft. You also may want to listen to the mix or instrument on large and small speaker systems. Too much energy in this range will make the mix sound muddy on large speakers played loud and still sound good on small speakers played at a medium volume. You want the mix or instrument to sound larger and more powerful over large speakers without sounding muddy. Rap, Hip Hop and "Dance" music (under various names) often have extra energy in the low-bass range. This is what causes cars equipped with sub-woofers to shake. Usually, however, it is not the entire mix that is boosted below 80 Hz, but just, for example, the foot drum. By boosting the energy on only one or two instruments, "clarity" can be achieved without "mud."
• Bass — Covering about 1.5 octaves, from 80 Hz to 250 Hz, this range of frequencies determines the "fatness" and "fullness" of the instrument's sound. Equalization is usually applied centered around two frequencies, 100 Hz and 200 Hz. For guitars and bass, the 100 Hz range tends to add body and fullness. Excessive energy in this range tends to make these instruments sound "boomy." This range of frequencies is still greatly affected by the Fletcher-Muson Effect; this means you will need to listen to the mix and instrument both loud and soft. Similar to how the 50 Hz range affects the bass and foot, the guitars should sound fatter when played loud, not boomy. Reducing the 100 Hz energy on the guitar will usually cause distinction between the bass and guitar parts. The lowest fundamental frequency on a guitar is around 80 Hz. For vocals the 200 Hz range determines the fullness of the vocal. This range can often be reduced to increase distinction on the vocal. If, however, boosting higher frequencies on the vocals makes the sound "thin" or "small" a boost of 200 Hz will restore fullness. When 100 Hz is reduced on a guitar or bass to reduce "boom," at small boost at 200 Hz can be helpful to keep the instrument from sounding "lumpy" (certain notes hard to hear and others standing out). The guitar and bass have almost equal energy at their fundamental and 2nd harmonic frequencies. Thus if a range of notes becomes hard to hear because of a at lot of 100 Hz, reducing energy at 100Hz and adding energy at 200 Hz will help the notes be heard again.
• Bass Presence/Low Mids — Covering about one octave from 250 Hz to 500 Hz, this range accents ambience of studio and adds clarity to the bass and lower-string instruments (Cello and Upright Bass). Equalization in this range is applied at many frequencies but most often between 300 Hz and 400 Hz.
The lower part of this range (250 Hz to 350 Hz) is sometimes referred to as "Upper Bass" and is used to increase distinction and fullness on the vocal, especially on female singers. The Lower Mid Range in general can be viewed as the "Bass Presence Range" Increasing this range gives clarity to the bass line.
• Mid Range - The Mid Range band of frequencies covers two octaves from 500 Hz to 2 kHz. This range can give a horn-like quality to instruments (500 Hz to 1 kHz) and a "tinny" sound (1 kHz to 2 kHz) or a telephone-like quality (all of the range). Equalization usually centers around 800 Hz and 1.5 kHz. The mid-range also tends to accent the presence (800 Hz) and attack (1.5 kHz). For Reducing 800 Hz on a vocal makes it sound less nasal and have more body and presence.
• High Mids — The upper midrange between 2 kHz and 4 kHz can mask the important speech recognition sounds if boosted, introducing a lisping quality into a voice and making sounds formed with the lips such as “m,” “b” and “v” indistinguishable. A small boost (1-3 dB) in the 3 kHz range for vocals will increase projection. Adding too much energy, in this range, makes it hard to distinguish the syllables of the vocal and can cause listening fatigue. This range of frequencies is often reduced on background vocal to give them a more "airy" and "transparent" sound.
• Presence — The presence range between 4 kHz and 6 kHz is responsible for the clarity and definition of voices and instruments. Boosting this range can make the music seem closer to the listener. Reducing the 5 kHz content of a mix makes the sound more distant and transparent.
• Brilliance — Covering approximately that last two octaves of sound (6 kHz to 20 kHz), this band of frequencies is responsible for the brilliance and clarity. Equalization centers around 7 kHz, 10 kHz and 15 kHz. The vocal "S" sounds are at about 7 kHz, making this a frequency that is avoided for vocals. Too much emphasis in this range, however, can produce sibilance on the vocals. Care must be exercised in reducing 7 kHz on vocals, however, because the vocal will sound dull very fast. The breath sound of the vocal is at 15 kHz and above, giving a breath quality without much accent on the "S" sound of the vocal.
Vocal EQing Techniques:
Roughly speaking, the speech spectrum may be divided into three main frequency bands corresponding to the speech components known as fundamentals, vowels, and consonants.
Speech fundamentals occur over a fairly limited range between about 125 Hz and 250 Hz. The fundamental region is important in that it allows us to tell who is speaking, and its clear transmission is therefore essential as far as voice quality is concerned.
Vowels essentially contain the maximum energy and power of the voice; occurring over the range of 350Hz to 2000 Hz. Consonants occurring over the range of 1500 Hz to 4000 Hz contain little energy but are essential to intelligibility.
For example, the frequency range from 63 to 500 Hz carries 60% of the power of the voice and yet contributes only 5% to the intelligibility. The 500Hz to 1 kHz region produces 35% of the intelligibility, while the range from 1 to 8 kHz produces just 5% of the power but 60% of the intelligibility.
By rolling off the low frequencies and accentuating the range from 1 to 5 kHz, the intelligibility and clarity can be improved.
Here are some of the effects EQ can have in regards to intelligibility.
- Boosting the low frequencies from 100 to 250 Hz makes a vocal boomy or chesty.
- A cut in the 150 to 500 Hz area will make it boxy, hollow, or tube like.
- Cuts around 500 to 1 kHz produce hardness, while peaks about 1 and 3 kHz produce a hard metallic nasal quality.
- Cuts around 2 to 5 kHz reduce intelligibility and make vocals woolly and lifeless.
- Peaks in the 4 to 10 kHz produce sibilance and a gritty quality.
|80 - 125||Sense of power in some outstanding bass voices|
|160 - 250||Voice fundamentals|
|315 - 500||Important to voice quality|
|630 - 1000||Important for a natural sound. Too much boost in the 315 to 1K range produces a honky, telephone-like quality.|
|1250 - 4000||Accentuation of vocals|
|5000 - 8000||Sibilance (the "S" sound - sizzling bacon sound)|
Effects of Equalization on Vocals
Easy-To-Remember 5 Golden Rules Of EQing
- If it sounds muddy, cut some at 250Hz.
- If it sounds honky, cut some at 500Hz.
- Cut if you’re trying to make things sound better.
- Boost if you’re trying to make things sound different.
- You can’t boost something that’s not there in the first place (cut before boosting).
For those of you who have an easier time visualizing the audio spectrum in one-octave increments (like those found on a graphic equalizer), here’s an octave look at the same chart.
|31 Hz||Rumble, "chest"|
|125 Hz||Boom, thump, warmth|
|250 Hz||Fullness or mud|
|8 kHz||Sibilance, definition, "ouch!"|
Tricks and Tips (Source: ArtistPro)
Use a narrow Q (bandwidth) when cutting; use wide Q’s when boosting If you want something to stick out, roll off the bottom; if you want it to blend in, roll off the top.
Boost a little at 125 Hz to 250 Hz to accentuate the voice fundamental and make it more “chesty”-sounding. The 2 kHz to 4 kHz range accentuates the consonants and makes the vocal seem closer to the listener.
Ed Seay: On a vocal sometimes I think, “Does this vocal need a diet plan? Does he need to lose some flab down there?” Or sometimes, “We need some weight on this guy so let’s add some 300 Hz and make him sound a little more important.”
David Sussman: If I’m recording vocals, I like to roll off quite a bit on the bottom end so the compressor doesn’t start kicking in and bringing up any low end rumble or noise. A lot of times I don’t need anything under probably 100 Hz.
Dave Pensado: I think of EQ as an effect much the same way you would add chorus or reverb to a particular instrument or vocal. Like, I might have a vocal where I think it’s really EQed nicely and then I’ll add a little more 3 kHz just to get it to bite a little more. Then it just makes me feel like the singer was trying harder and it brings out a little bit of passion in his or her voice. So I tend to be most effective when I do the standard equalizing, then take it to the next level, thinking of it as an effect.