Using EQ.pdf

Using EQ

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Paul White and Mike Senior explain how to get the best practical results from

equalisation by understanding the true frequency ranges of most instruments and

voices.

An understanding of the variety of different equalisation tools

at your disposal can help in choosing the most suitable type

of processing for any situation. However, using equalisation

is about much more than just selecting the correct unit and

this month, we will be looking at how best to employ

equalisation techniques in music production.

The first challenge when equalising musical sounds is in

deciding which area of the frequency spectrum corresponds

to which element of a sound's timbre. If you're wanting to

emphasise the click of a bass drum, where should you

boost? Alternatively, if your guitar sounds boxy, where can you cut most effectively?

Pitch & Frequency

One thing that can help a little in deciding this is to know what frequencies correspond to

the fundamentals of each musical pitch. For a start, this allows you to define the lower limit

of the range of frequencies generated by pitched sounds. Figure 1 shows how the pitch

ranges of various common instruments, and hence how the ranges of their fundamentals,

relate to frequency. You can see from this that you're not likely to get much in the way of

useful tonal change if you try to EQ a violin part below about 150Hz, for example. The most

noticeable effect of boosting most instruments below their fundamental frequencies will

probably be an increase in the level of any noise lurking in the depths. Indeed, there is a lot

to be said for using a high-pass filter to cut any unused low-frequency range, in order to

prevent unwanted noise from obscuring other recorded parts in your mix.

Knowing the frequencies corresponding to certain pitches can also be useful when

attempting to remove unwanted pitched elements, such as hum, from sounds. If you know

the frequency of your mains hum (50Hz in the UK) then you can apply cut with a narrow

peaking filter to notch out the 50Hz fundamental or its most prominent harmonics. In such

cases it's worth bearing in mind that real-world pitched sounds usually have appreciable

levels of harmonics, and that these occur at multiples of

the fundamental frequency, so you'd want to experiment

with notching at 100Hz, 150Hz and 200Hz as well, if you

were going to seriously reduce the hum in this example.

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(Having said this, serious hum problems are very difficult

to solve even using multiple peaking filters, as their EQ notches are often insufficiently

narrow to avoid damaging wanted components of the sound. In these cases, a dedicated

digital noise removal device or software package will probably be more successful and

produce fewer audible side effects.)

Similar EQ'ing techniques can also be used to emphasise pitched elements in percussive

instruments -- some producers find that this can lend these sounds greater punch. The trick

is to decide what pitch the instrument suggests most strongly, and then to array a set of

very narrow peaking filters to boost the fundamental and harmonics of this note.

Exploring Instrumental Timbres

However, there is only a limited amount of practical use for the table in Figure 1 when

learning about how to EQ. It's not the pitch associated with a given EQ frequency which is

normally of primary concern, but rather the tonal change which is associated with boosting

or cutting in that region. And the only way to learn about this effectively is through running

some sounds through an EQ unit or plug-in and experimenting.

The easiest way of identifying the frequencies corresponding to particular timbral

characteristics is to crank up the boost control of a peaking filter, with its Q value set to

about three or four, and to sweep it through the spectrum listening as each element of the

range is boosted. It can also be useful to stop the peak over a particular area and then to

switch the EQ in and out to get a feel for the effects of boost in that region. With a little

practice using different sources, you ought to start getting a feel for the unique

characteristics of each sound.

As a guide in learning about the effects of different EQ frequencies on different instruments,

check out the boxes which appear throughout this article. These compare the frequency

balance of similar instruments within different well-known commercial tracks, and therefore

can provide a point of reference for you when recalling which frequencies you need to

address for your own recorded sounds.

The Drumkit

BASS DRUM

The punch component of most bass drums lies between about 80

and 100Hz, and meaty kicks such as those in AC/DC's 'Back In

Black' and Britney Spears' 'Baby One More Time', tend to have a

lot of energy in this range. Below this area, you'll mostly feel,

rather than hear, any boost, and it's easy to overdo. Warmer kick

sounds, such as those in James Brown's 'I Got You (I Feel Good)'

and Stevie Wonder's 'Sir Duke', major on the 200-300Hz region.

Where the kick needs to cut through on smaller speakers, then

you might also consider a boost in the region of 2.5-6kHz, which

will tend to emphasise the click of the beater. As an illustration of

the sort of effect this has, compare the lack of any bass-drum click

in the James brown example with the aggressive kick sound in the

Madness single 'My Girl'.

SNARE DRUM

The fatness of the snare tends to reside between 120 and 400Hz, and the aforementioned AC/DC and

Britney Spears examples are both powerful in this area. A boxy sound, such as that on the Guns &

Roses song 'Sweet Child Of Mine' is indicative of comparatively high energy in the 800Hz-1.2kHz

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range, whereas the resonances of the drum's ringing reside above this, between about 2-4kHz -- a

frequency region showcased in the snares of Bob Marley's 'Get Up Stand Up' amongst many other

reggae tracks. The crispness of the drum's attack tends to reside more in the 4-8kHz region, and the

Sister Sledge track 'We Are Family' heavily emphasises this frequency on its otherwise fat snare

sound.

TOM-TOMS

Floor toms can be made fuller around 100Hz, while rack toms respond in a similar way up to about

300Hz -- the 'Sir Duke' toms are characteristic of boost in this range. The ringing or rattling of the skins

occurs at about 1-3kHz, as is evidenced on Iggy Pop's 'Lust For Life' and the drum solo in the Beatles

'The End'. The Iggy pop example also emphasises the attack of the toms, which is higher up the

frequency range between about 4 and 8kHz.

CYMBALS

Although Cymbals are associated with high frequencies, a boost between 100 and 300Hz can help to

emphasise the clunk of the stick on a ride cymbal or hi-hat, something particularly noticeable in

Donovan's 'Mellow Yellow', for example. The ringing overtones of crash and ride cymbals can be

brought up within the 1-6kHz area, an area characteristic of the sound in Led Zeppelin's 'Rock & Roll',

while the sizzle of any of the cymbals can be emphasised in the 8-12kHz range -- check out Metallica's

'Enter Sandman' or Michael Jackson's 'Billie Jean' for examples of this.

Setting EQ Gain

Getting to know the frequency ranges associated with different elements of an instrument's

timbre is useful, but what you really want to know is how to use that information to best

effect when applying EQ to real signals. Perhaps the first basic piece of advice to take on

board is that it's best to apply as little EQ as you can when sorting out tonal problems,

especially if you don't have access to a really nice-sounding equaliser. Any processing you

use has the ability to degrade the sound just by dint of the extra processing components

within the signal path, so it's important to make sure that the cure is better than the disease!

If you only have access to budget equalisation (whether hardware or software), it is usually

worth taking extra care to get sounds right at source, rather than having to rely on dodgy-

sounding processing to fix anything in the mix.

Consider trying out different equalisers if you have a choice. All equalisers sound subtly

different even with the same nominal settings, and you will find that different models

respond in different ways to the same signal. The difference between digital and analogue

equalisers is a good case in point. Because good analogue equalisers induce musically

useful phase changes in the audio passing through them, they can cause a significant tonal

change even with less than a decibel of boost applied. On the other hand, digital equalisers

can be designed to leave phase relationships almost unchanged, so large gain settings can

be made less noticeably.

A second general rule is that it's usually better to apply EQ cut than EQ boost if you want to

avoid the processing being too obtrusive. This is especially relevant when using high-

resonance peaking filters for treating narrow sections of the audio spectrum -- the filter will

have a tendency to 'ring', unnaturally emphasising and extending sound at its centre

frequency. It follows, then, that you should try EQ cut to solve localised problems, using a

bandwidth narrow enough to achieve the desired effect without unduly altering adjacent

frequency ranges, whereas EQ boost should be over wider b andwidths and using as little

gain as will suffice. For example,

getting rid of an unwanted vocal

resonance may need several

decibels' cut with a fairly narrow

Strings & Brass

STRING SECTIONS

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bandwidth, whereas adding high-

end gloss to a mix needs only about

a decibel of high-frequency boost

with a wide bandwidth setting.

The 200-300Hz range is great for giving a string section a

fuller sound, characteristic of tracks such as The Beatles

'Eleanor Rigby' and The Rolling Stones' 'As Tears Go By'.

Much of the mid-range timbre will depend on the forces

used, so it's difficult to generalise here. However, in the

high-frequencies, the 7.5-10kHz range emphasises bow

and string noise, as in The Beatles 'Yesterday', and larger,

smoother string sounds, such as that on Massive Attack's

'Unfinished Sympathy', may benefit from cut in this area.

Boosting with EQ is best kept to a

few decibels if you're after natural

results, but narrow-band cutting can

be made much deeper to get the

desired result. In fact, if the

maximum cut provided by a single

peaking filter is not enough, you can

even set a second peaking filter to

simultaneously cut the same

frequency for a deeper notch. It is

worth mentioning here, however,

that EQ cut has just as much impact

on the internal headroom of your

equaliser circuitry (or algorithm) as

EQ boost, so a poorly designed

equaliser might well produce

undesirable sonic artefacts if you

layer two peaking EQ bands in this

way.

BRASS SECTIONS

Recordings of brass sections can be warmed up by

boosting between 200 and 400Hz, and Donovan's 'Mellow

Yellow' exhibits a sound characteristic of this. A more

honky sound, such as on Aretha Franklin's 'Respect' can

be found at 1-3.5kHz, whereas the rasp in Stevie Wonder's

'Sir Duke' resides in a range higher than this, at about 6-

8kHz. Swing Out Sister's 'Breakout' also has a lot of rasp,

but with additional shrillness in the 8-12kHz region as well.

SOLO TRUMPET & SAX

The warm sound of the trumpet in The Kinks' 'Dead End

Street' has a lot of energy in the 200-400Hz region, as

does the warm sax solo in James Brown's 'I Got You (I

Feel Good)'. By way of contrast, the solo sax in The Stereo

MCs' 'Connected' is lacking in this region, with extra boost

in the nasal 1-3kHz range. The solos in Dire Strait's 'Your

Latest Trick' demonstrate the brightness that can be added

at 6-8kHz, while Touch & Go's 'Would You' is almost

painfully shrill as a result of high energy in the 8-11kHz

region.

As we saw in last month's

Equalisers Explained article, a filter

can affect the levels of frequencies

well beyond its centre or cutoff

point. If you find that a deep notch

at one frequency is also attenuating nearby wanted components, then try applying a little

boost with another fairly narrow peaking filter to the affected area as a way of

compensating.

While you're working towards the best possible setting, keep using the equaliser's bypass

switch to compare the sound of your processing with the unprocessed original sound. If

you're EQ'ing at mixdown, you'll also want to evaluate your EQ changes in the context of

the mix, rather than while the sound in question is soloed. After all, it's no use getting

individual parts sounding brilliant in isolation if they don't work together in the mix. Bass

guitars are particularly prone to disappearing in the mix even when they sound amazing on

their own.

Equalisation Or Enhancement?

A mistake often made by newcomers to recording is to try to brighten an inherently dull

sound by applying large amounts of treble boost. This rarely achieves more than an

increase in background noise and grittiness. The finger of blame is then often pointed at the

equaliser when the real problem is a lack of understanding. An equaliser can only boost

high frequencies where they exist in the first place. A synthetic sound with no top end, or a

miked Fender Rhodes piano played through a dull-sounding amp with limited bandwidth

speakers, will not respond well to high-frequency boost because that frequency contains

mainly noise and interference.

In such cases, using a psychoacoustic enhancer may yield better results, because it

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processes the frequencies that are present in the original signal (usually via compression,

filtering and controlled distortion) to produce extra high-frequency harmonics designed to

augment the existing signal. Because the added harmonics are related to the existing

signal, the ear accepts them as being 'real', and a part of the sound as a whole. Although

enhancers need to be used sparingly, to avoid producing a harsh or unnaturally abrasive

result, they can often rescue sounds that EQ cannot deal with.

Guitars & Basses

ACOUSTIC GUITARS

Boosting at around 80-120Hz gives a low-end weight, such as in The Beatles' 'Yesterday', whereas the

sound gets more of a boom to it a little higher at 200-300Hz, as in Nirvana's' 'Polly'. This latter song is

also a good example of boost in the 2-5kHz range, which is good for clarity in rhythm guitars as it

brings out the strumming. The 1-1.5kHz area, prominent in The Jam's 'That's Entertainment', can tend

to sound a little nasal, while the 5-10kHz range emphasises the jangle or sparkle of steel-strung guitars

in particular, Natalie Imbruglia's 'Torn' being a notable example.

ELECTRIC GUITARS

Electric guitars are rather a law unto themselves, as their tonal balance varies so drastically from style

to style. However, there are a few general principles to bear in mind. The first is that there will be little

other than hum and noise below the guitar's fundamental frequency, so it's often worth filtering below

about 80Hz. However, most guitar sounds can be warmed up with a boost at around 125-250Hz, as

you can hear from the guitars in Metallica's 'Enter Sandman'.

The other main thing to take into account is that the frequency response of most guitar speaker

cabinets rolls off pretty steeply above 4kHz, and so your best choice for emphasising the crispness and

attack of guitar sounds is a boost at 3-5kHz -- frequencies to the fore in Nirvana's 'Smells Like Teen

Spirit' and Chuck Berry's 'Johnny B Goode', for example. Any boost well above this is likely to increase

only noise levels, so if you want an even more cutting lead sound, such as that in Guns & Roses

'Sweet Child Of Mine', you might consider using a psychoacoustic enhancer as well.

BASSES

Basses get most of their weight from the 80-100Hz region, and pop ballads such as Shania Twain's

'Still The One' will usually pack a punch in this range. For a more overtly warm sound, the 100-300Hz

region can be boosted. Extreme examples of this quality include the electric bass parts in The Beatles

'Come Together' and Bob Marley's 'I Shot The Sheriff', as well a the upright bass in Ben E King's

'Stand By Me'.

Greater attack, though not without a little boxiness, is available at around 500-1500Hz. The

Temptations 'Papa Was A Rolling Stone' and The Strangler's 'Peaches' exemplify boost in this region

for fretted bass, while Paul Simon's 'Graceland' and The Cure's 'Lovecats' show it off on fretless and

upright basses respectively. A more jangly sound with emphasis on string and fret noise, such as in

Nirvana's 'Lounge Act' or the Red Hot Chili Peppers' 'Give It Away', can be found by boosting between

about 2 and 5kHz. A high shelving boost above about 2kHz might be more suitable if you're after string

noise and an airy tone with upright bass parts, though, as in Lou Reed's 'Walk On The Wild Side'.

Vocals

Vocals tend to boom when boosted around their fundamental frequencies, with 'Exit Music (For A Film)'

by Radiohead and 'Peach' by Prince exemplifying the effects of such processing. Plosives and

handling noise can be reduced by cutting below about 100Hz, though this improvement needs to be

balanced against the side effects for the rest of the vocal sound.

Nasality can be addressed at around 1-3kHz, while the 4-5kHz range can be boosted for more

presence. If the extremes of the frequency spectrum are removed to leave only these tonal areas, then

you can get the 'telephone' special effect which will be familiar from tracks such as White Town's 'Your

Woman' and Space's 'The Female Of The Species'.

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