Important Equalization Frequencies

50 Hz

+
fullness to low freq instruments – foot, bass, floor tom
-
decrease the “boom” of the bass and can increase recognition and overtones of the bass line in the mix. Often used in rock

 

100 Hz

+
harder bass sound to low freq instruments
fullness to guitars, snare
warmth to piano and horns
-
remove boom on guitars & increase clarity

200 Hz

+
fullness to snare and guitar (harder sound)
fullness to vocals
-
decrease muddiness of vocals or mid-range instruments
decrease gong sound of cymbals

400 Hz

+
clarity to bass lines especially when speakers are at low volume
-
reduce to decrease “cardboard” sound of lower drums (foot and toms)
reduce to decrease ambiance on cymbals

800 Hz

+
increase for clarity and “punch” of bass
-
reduce to remove “cheap” sound of guitars

1.6 KHz

+
increase for “clarity” and “pluck” of bass
-
reduce to remove dullness of guitars

3.15 KHz

+
increase for more “pluck” of bass
increase for more attack of electric / acoustic guitar
increase for more attack on low piano parts
increase for more clarity / hardness on voice
-

reduce to increase breathy, soft sound on background vocals
reduce to disguise out-of-tune vocals / guitars

 

5 KHz

+

increase for vocal presence
increase low frequency drum attack ( foot / toms)
increase for more “finger sound” on bass
increase attack of piano, acoustic guitar and brightness on guitars (especially rock guitars)

-

reduce to make background parts more distant
reduce to soften “thin” guitar

 

7 KHz

+

increase to add attack on low frequency drums ( more metallic sound )
increase to add attack to percussion instruments
increase on dull singer
increase for more “finger sound” on acoustic bass
increase to add sharpness to synthesizers, rock guitars, acoustic guitar and piano

-

reduce to decrease “s” sound on singers

 

10 KHz

+

increase to brighten vocals
increase for “light brightness” in acoustic guitar and piano
increase for hardness on cymbals

-

reduce to decrease “s” sound on singers

 

15 KHz

+

increase to brighten vocals (breath sound)
increase to brighten cymbals, string instruments and flutes
increase to make sampled synthesizer sound more real.

-

Equalisation – Practical Applications

equalization-practical-aplication

How one chooses to apply EQ depends on a number of factors. The style of music, the instrument, the quality of the recording, the musical arrangement, the production values, and personal taste, all have a role to play. There is no single approach that will guarantee a fantastic mix. Different musical styles require different sounds and so EQ has a role in shaping that. A pop piano will typically be much brighter and harsher sounding than a jazz or classical piano when a more warm rounded tone is required. Certain high tempo dance styles demand an almost punishing bright high hat tone whilst if you’re creating more chilled-out music with old loops and you’re adding a hat, then a more middly EQ will help the hat to sit well with the other sounds. Here are some general pointers for applying EQ to specific instruments.

[box type=”note”]Removing rogue frequencies: If you want to isolate an unwanted frequency and then remove it, here is a tried and tested technique. Use a parametric EQ and set it to a narrow bandwidth, and a high boost. Move the frequency control around until the unwanted frequency is at its worst. Then change the boost to a cut and adjust the bandwidth so as to achieve maximum removal of the rogue sound with minimal impact to the wanted sound.[/box]

Vocals

In the low frequency area some vocal recordings can suffer from explosive “pops” from ‘pis and Vs when mic technique and pop shields have failed. Applying a high pass filter can work although it might affect the warmth of the vocal. If the pops are infrequent you could automate when the filter is active so that it only works on the unwanted pops. Alternatively you could isolate the popping frequency and remove it as described above.

Vocals tend to have plenty of mid range presence naturally, but if the vocal is a bit nasally this can be modified in the 1- 3kHz area. Adding a little lift at around 4-5kHz can give a nice airy sound and helps with intelligibility.

7-8kh are good for De-Essing (if you have lot of sibilance in recorded vocal)

A gentle boost around the 12-18kHz area can add crispness and enhance the inherent detail in the recording often people refer to this as adding “air’ to the sound.

When mixing lead and backing vocals, or different BV parts avoid applying identical eq treatments. Try slightly different frequencies as this can thicken the sound and help the two parts to work together. If stacked BV parts are slightly duller than the lead this can help bring the lead vocal to the front of the mix, A slight cut above 10kHz on the BVs with a corresponding boost to the lead in the same area should have this effect.

 

Acoustic Guitar

EQ requirements for acoustic guitar can be particularly dependant on the quality of the recording. They can often sound “boxy” or “boomy” if the mic(s) were too close to the soundboard due to the precedence effect.You can often deal with this by rolling off the very low end or introducing a slight dip between 200 and 500Hz. A more solid, orderly sound can often be achieved by enhancing tones around the IkHz area, whilst you can improve clarity by boosting at points round 2.5kHz, 3.5kHz and 5kHz. Above 5kHz you will probably emphasize string squeaks, fret noise and even player breathing — which may or may not be desirable.

 

Bass Guitar

A typical bass sound will not contain a huge amount of sub-bass (below about 60Hz) frequencies. That’s why the b parts of a well-mixed track can still be heard in small transistor style radios. A lot of the bass activity actually occurs low mid area around 150-500Hz. So experiment here. A clean DI-ed bass often sounds great on its own but disappeared the mix so adding so low mid can help it to stand out. A touch of distortion or overdrive in a pop or rock mix can bring harmonics in this area and achieve a similar effect.

Sometimes bass can be made more manageable by actually filtering out some of the very extreme low end below 5 this is not an essential element of your music) this seems counter intuitive to the novice but makes sense when you consider that most 4 string electric bass fundamental notes will not be in that frequency range anyway. Most domes playback systems can’t reproduce below 50Hz anyway and these frequencies take up headroom and can place unnecessary stress on your speakers.

The frequencies that correspond to “warmth” and “fullness” are usually considered to be between 80 and 200Hz so adding a little here if this is what your bass is lacking. If your bass has too much of this and the sub frequencies it perceived to be muddy so cutting would be appropriate. If the bass sounds a bit “honky” or “boxy” try to reduce the frequencies around 500 — 1Khz, On a bass guitar you can sometimes add sustain and definition by increasing the frequencies around lkhz. You can add clarity by emphasizing attack and string noise at 2.5kHz.

 

Electric Guitar

Electric guitar is very difficult to make generalisations about since the range of sounds and playing styles isso huge. Searing solos, heavy distorted chords and riffs, choppy rhythms, funky muted picked parts, and ambient chordal we example, would all have different roles within a mix and therefore all require different approaches. We can say  in most cases there would be little but noise and hum below the guitar’s fundamental frequency so a low and roll-of can be a good starting point. “Warmth” can usually be added around 125 to 250Hz. Most guitar speaker cabinets tend to have a frequency response that begins to taper off above 4kHz so if you are looking for crispness and attack 3-5kH good area to work on.

More specifically. “Chic” style funky choppy guitars would tend to have the low frequencies taken out, and the middle and top and 3.5 and 5Khz boosted. “Bluesy” guitars sounds tend to have more of the low end. For chunky heavy metal guitars boosting around 350kHz can add weight. Sometimes effects boxes and distortic especially can over brighten the sound and worse still add high frequency hiss so it’s a common technique to use high pass filter and roll off above 7kHz to get rid of this. This is especially true of the modern “metal” shredded sound.

 

Piano

As we mentioned earlier piano sounds are very particular to musical styles. And unlike most other orchestral instruments it covers a very wide range of frequencies. EQ settings are very dependent on the style and the musical arrangement. If an acoustic piano has been well and appropriately recorded it is probably best to try to avoid EQ at all so as to maintain the most natural sound. However if your piano is muddy or not warm enough then look at the 150-300Hz territory, if you’d like a bit more presence then go for 2-4kHz.

 

Drums

Bass Drum

Bass or kick drums sounds tend to be made up of a transient click followed by a deep tone that gives character. The weight of the tone tends to lie in the 65-110Hz area. Try boosting here if you require more weight. Below this you’re more likely to feel the difference rather than hear it so be careful not to overdo it, after all, unless you have full range main speakers or a correctly calibrated sub bass you could actually be adding sub bass that’s doing more harm than good. Warmer kick sounds feature more energy in the 200-400Hz department, however, there can be unpleasant “boxy” resonance so often a subtle cut is used here if that is the case with a parametric EQ. This can help the sound to cut through on smaller speakers. The initial transient can be emphasized by boosting in the 2.5-6kHz region. Rock albums since the late 80′s have often had quite an aggressive boost on this region to bring the “click” of the beater impact out.

Snare Drum

The weight or “fatness” of a snare drum will tend to lie in the 150-400Hz range. If you want to add or reduce “boxy-ness” go for around 800Hz to 1.2kHz. Depending on the particular drum the ringing resonance of the snare can be found above this up to about 4kHz. Emphasizing the ring may or may not be desirable depending on taste and musical style. Dance and funk styles often have very dead weighty snare sounds whereas rock snares are much more ringing and ‘live’. If you need to remove a nasty resonant ringing sound use the technique above for removing rogue frequencies. Adding a little in the 4-8kHz region will give a more crisp, tight sound.

Tom Toms

Floor toms can sound fuller with a boost around 100Hz. The same goes for the rack toms at about 300Hz, if you want to emphasize a toms ring or resonance this would usually be in the 1-3kHz area and the attack can be enhanced between 4-8kHz.

Cymbals

Cymbals and hi-hats often don’t have much competition for the very high frequencies so they tend to stand out very easily. Sometimes it’s a questions of EQ ing them so that the blend more rather than stand out. Its not uncommon on a fully close mic’ed kit to use high pass filters and roll out the sub bass so the spill doesn’t smear the definition of the close mic’ed Kick/bass drum typically up to 120hz and often as high as 330hz. You can get a more clunky sound with the stick of the hi-hat by going for 100-300Hz, and you can emphasize the ringing over tones of crash and ride cymbals between 1- 6kHz. If the sizzle of the cymbal is most important part for your mix then boosting a little around 8-12kHz will help, but be careful though before boosting these high frequencies, unlike 2 inch tape that saturated and rolled off the extreme higher frequencies digital recordings leave them in do you really need any more?

 

Strings

If you’re working on solo strings they can be fattened up at around 250Hz and boosting 7-10kHz will emphasize the scratching and edginess of the bowing. String pads can cover a very wide range of frequencies so its difficult to make generalisations. But, as with the solo string, warmth can be found at around 250-300Hz, sweetness at around 3-5kHz and sheen around 8kHz and above.

 

Brass

Mellow brass parts can be emphasized around the 100Hz to 300Hz range. Presence can be added between 3 and 5kHz. You can bring out the rasp around 6-8kHz and shrillness from 8-12kHz.

Types of EQ

types-of-eq

There are several types of eq. Let’s have a look at each general type of filter which is commonly used in equalisation process.

 

High Pass Filter

high-pass-filterA high pass filter does what it says on the tin. It allows high frequencies to pass through it and attenuates all others. On
analogue desks this type of filter would often have appeared as a switch with a predetermined roll-off frequency of
between 50-120Hz. This would mean that all frequencies below 120Hz would be attenuated at a particular rate. The rate is know as the slope of the filter and is defined in terms of dB per octave. Typically a high pass filter would attenuate at a rate of —6, -12, or —18dB per octave although in the digital domain —24dB per octave is not uncommon. We know that
every time we descend an octave the frequency is halved. This means that if the HPF has a slope of —6dB per octave and the filter starts at 120Hz then at 60Hz the level is 6db lower. On a technical note, any frequency that is attenuated by less than 3dB is said to be within the pass band. The cut-off frequency is where the filter has already attenuated by 3dB. Frequencies that are attenuated by more than 3dB are said to be in the stop band. A low cut is a HPF with a slope of -18 or —24dB per octave.

Low pass filter

low-pass-filterA low pass filter works on exactly the same principles as a high pass filter except that it operates at the other end of the frequency spectrum. It lets all the low frequencies pass through and attenuates the high ones.

High and low pass filters are used for removing unwanted frequencies at either end of the spectrum where the wanted frequency will not be affected by the cut. For examplere moving low rumble from a vocal track or perhaps removing high hat spill from a snare track. In recent years they have also been used to great effect in dance music production. Drum tracks or even whole mixes are subjected to a low pass filter that gradually moves down the frequency spectrum cutting out almost all the high frequencies so that the music sounds as though it is being played in a next door room. The filter is then opened out again at a suitably dramatic point in the music for a great build up. High pass filters are often used on drum loops during a drop giving them a small and tinny sound. The filter is then opened out again suddenly or gradually at the end of the drop section giving a sharp or a smooth transition back into the main musical theme, as desired.

 

Shelving Filters

Shelving filters are a much more musical type of equalisation than HP or LP filters. They are designed more for gentle overall tonal shaping than for keeping out rogue frequencies. Rather than introducing an increasing gain change above or below a certain frequency, shelving filters apply an equal amount of cut or boost to all frequencies above or below the designated shelving frequency. Typically there would be two controls one for selecting the frequency and the other for selecting the amount of gain change. The transition from the OdB reference point to the designated cut or boost level of the shelf is not immediate and so this type of filter also has a slope. Whilst it would be theoretically possible, in the digital domain, to design filters that arrive at the shelving frequency almost immediately, these have been found to be less musically pleasing and thereby less useful for audio processing than those with a gentle slope.

shelving filter

 

Band pass filter

bandpass_filterA band pass filter passes frequencies between two limits. It is effectively a low pas! and a high pass filter working together. Typically this filter would have controls for determining the central frequency and the bandwidth (the distance, in frequency terms, between the high and low cutoff points). This type of filter can be used for isolating a narrower band of frequencies in recordings that have too much high and low end or more typically it is used as an effect to create that nasally mid range typ of old radio voice sound that we all know and love! Band pass filters are also very widely used in synthesizer design and you can create interesting effects by using a narrow bandwidth and moving the central frequency around.

Notch filter

notch-filterA notch filter does the opposite to a band bass filter. It is also know as a band reject filter. Frequencies above the upper cutoff and below the lower cutoff points are unaffected whereas frequencies in between are cut or boosted. A notch filter
enables you to zone in on a narrow frequency band and boost or cut at that band. Notch filters are generally used for eliminating rogue or unwanted frequencies that -20 fall in the mid range rather than at the extremities where you would use a low or high pass filter. This is great for such jobs as removing an unwanted “ringing” resonance from a snare drum or removing “muddiness” in the lower mid range from drum sounds. It’s also good for creating frequency space in the mid range if you have two or more sounds with clashing or overlapping frequencies.

 

Peaking filters and Parametric Equalisers

With a peaking filter, the user is able to select a frequency and cut or boost the level of the sound around that frequency. A standard peaking filter (or semi-parametric EQ) will have controls for gain and frequency. A parametric EQ is a peaking filter with an additional control for bandwidth or Q. It is so-called because (dB) each of these parameters is adjustable. The bandwidth (see below) determines the spectral spread over which the EQ iseffective. As with other filter types the bandwidth is described from the point at which has been cut or boosted by 3dB from the unaffected level.

[box type=”shadow”]Bandwidth or Q When boosting a frequency with a parametric EQ, the user is not just boosting a single frequency alone but also those immediately surrounding it. As with other filter types there is a slope. The gradient of this slope depends on two things, the amount of cut or boost and the width of the frequency band that is included. A wide bandwidth will affect a broader range of frequencies than a narrow one. Q and bandwidth describe the same thing but using inverse scales. Bandwidth describes the number of octaves (or fractions of an octave) that are included in the cut or boost range. Q is given as a number whereby a high Q value denotes a narrow bandwidth and a low one a large bandwidth. A Q value of 90 (approx.) means that the bandwidth is 1/60th of an octave. A Q value of 0.4 (approx) would denote a bandwidth of 3 octaves.[/box]

This is an extremely powerful type of equaliser with a huge variety of uses. A parametric EQ with a wide bandwidth can be used for general tonal shaping over the middle frequency range. Alternatively a very narrow bandwidth can be used to pick out and remove nasty resonance — performing a similar role to the notch filter. A moderate bandwidth setting could be used for emphasizing an instrument by tracking down the frequencies that give it presence and character and boosting them to taste. A narrow bandwidth, and a high boost can be used for creative special effects if the peak or resonant frequency is swept over time using automation or an LFO.

 

Graphic Equaliser

Most of us are familiar with the graphic equaliser. They are not commonly used in DAWs for mix purposes but deserve a mention since they are the type of EQ that is most commonly found in the outside world. They are widely used by hi-1 enthusiasts, in PA systems and studio control rooms and of course in cars. A graphic EQ has a number of clearly labelled frequency bands each with a dedicated fader and a detent point for zero boost or attenuation. There should be little or no interaction between the frequency bands and there is usually about 12 dBs of cut or boost. According to the ISO (International Standards Organisation) the stages (frequency bands) should be 1/3 of an octave apart. This means that when you reach the 4th stage it will be double the first. 

Graphic EQs are used in PA rigs to deal with feedback and bad acoustic resonance. In control rooms they can help to correct monitoring anomalies.

 

 

 

 

Introduction to Equalisation

equalisation

Equalisation or EQ is perhaps the most fundamental tool of the mix engineer. He/she must determine what contribution each element should be making to the frequency spectrum of the mix as a whole and also determine which elements are fighting for the same frequency space. If the aim is for clarity, then the job of the mix engineer is to enhance the essential frequencies for each instrument and reduce or filter out unnecessary ones so as to create space in the spectrum for all the instruments. Clearly, the greater the number of tracks, and the more complicated the production, the tougher the job for the mix engineer. Although it is important to listen to sounds in isolation, it is how they react with each other in the context of the mix that is of ultimate importance. When applying EQ always check both in solo – to know exactly what you’re doing — and in the mix — to appreciate the effect, It can be very easy to over EQ so don’t necessarily be tempted to apply EQ automatically. Think of it as a tool to fix a problem, enhance a sound or create an effect.

We know that the human ear can hear sounds ranging from 20Hz to 20kHz. Conceptually engineers and musicians tend to divide the spectrum into 3 to 5 bands. Here is a rough guide as to where these bands sit.

  • The low frequency band is roughly from 20Hz to 150Hz/200Hz
  • The lower middle frequency band is roughly from 200Hz to 800Hz
  • The middle frequency band is roughly 800Hz to 2000Hz
  • The high middle frequency band is roughly from 2kHz to 8kHz
  • The high frequency band is roughly 8kHz to 20kHz

We noted earlier that we do not perceive pitch in a linear fashion. This is reflected in the way we think about the frequency spectrum in engineering and musical terms. In terms of Hertz the frequency bands, as we perceive them are not divided up evenly at all as you can see.

The musical arrangement will dictate the range of frequencies you’ll hear in a mix but in general there will be a good spread of low, mid and high frequencies. For the engineer it is useful to know which instruments typically sit in which frequency bands so as to have an idea how they will fit together in the mix.

Some instruments such as the drum kit for example have components that spread across the whole spectrum. The kick or bass drum will fall into the low frequency band, the toms into the low mid band, the snare into the mid band and the high hats and cymbals into the mid high and high frequency bands.

The components of an orchestra also tend to follow this kind of pattern. For example in a string section we have the double bass covering the low frequencies, the cellos covering the low mids, the violas right in the middle and the violins in the upper mids and highs.

A typical band set-up might comprise kick drum and bass in the low frequencies, toms in the low mid area, snare, keys guitars and vocals ranging across the middle frequencies and high hats and cymbals in the high frequency band. The middle frequency range is the area where our ears are most sensitive, and also the area where many different instruments tend to overlap in the frequency domain competing for space. This is often the trickiest area for the mix engineer to deal with.

 

Knowing which frequencies correspond to which pitch, and the frequency ranges of the pitched notes of various instruments, can be useful to give an idea of where various frequencies are. The lowest note on a violin corresponds to 196Hz so you’ll not get much joy EQ-ing below this. You’re more likely to bring out unnecessary low frequency artefacts. However, above that, of course, the pitched notes will have fundamentals and harmonics that go way above the fundamental frequency of the highest pitched note. A good way to get to know frequencies for EQ purposes is to set a parametric EQ with a narrow bandwidth and high gain and sweep the frequency around on the track you have chosen. You’ll soon get an idea, which frequencies correspond to which timbral characteristics of the sound you’re working on. People tend to use rather imprecise terms when discussing these characteristics such as warmth, depth, muddy, woolly, nosey, honky, crisp, harsh, bright, and airy. It’s the job of the engineer to interpret these terms and know where the frequencies are which roughly correspond, This comes with a little time and practice.