Guide to EQ

I found a masterclass extensive guide to EQ, so here you go:

There are many urban myths surrounding the use and abuse of equalisation in the studio, and sorting out myth from madness can be a tricky business. Often, when questioned, famous record producers and engineers will state: 'I don't really use EQ'. However, if you get the chance to work with these people, you'll discover that the EQ is frequently switched in. What they are really saying is that whenever possible, they try to avoid using equalisation as their primary sound-shaping mechanism. In fact, in most cases, they still use EQ as much as anyone else in order to make quality recordings without changing the fundamental character of the sound - this is just good recording practice.
Unfortunately, many sound professionals don't like discussing exactly what they get up to with EQ, fearing they might give away their personal secrets. And that's why we've decided to bring you the facts about EQ - no nonsense, no hype, just plain and simple truths to make you more confident about when to (and when not to) reach for those knobs.

Why use EQ?

The name 'equalisation' comes from the original intent of the invention - to make the final recorded sound equal to the original source, making up for inadequacies of both the equipment and the recording environment itself. This is an art that is, unfortunately, being lost. In the first part of this article, then, we will explore several different equalisation techniques that are used during the first part of the recording process: tracklaying. Some of these are old, and some are new - but all are techniques that you should be aware of. All are quite unrelated to the kind of creative sound-shaping that many people resort to all-too-quickly when recording and mixing a track - we'll be looking at those in next month's article.

Noise reduction

A fundamental part of recording is to get the best signal down to 'tape', and extraneous noise can be a nuisance. This can be EQ'd out, but when it comes to getting rid of unwanted noise from a signal, it's better to get the sound right at source, solving the problem once and for all. If you persistently get, for example, a hum on your electric guitar, it's much better to track down and remove the source of interference for good, instead of remembering to roll off the bass every time you record. If you don't take this kind of action whenever possible, it can substantially limit your ability to make more extreme, creative adjustments later on.

Unfortunately, there are many sources of unwanted background noise when recording, such as rumbles, bumps and bangs, popping, hums, hiss and instrument spill. Let's take a look at what we can do about them...

Rumbles

Background rumbles can come from a number of sources. In a purpose-built studio, air conditioning systems are a prime suspect. Nearby traffic (and in locations such as central London, tube trains) can generate very low frequency rumbles that aren't noticeable when standing in the room, but on a high-quality microphone at a high gain setting, can be unacceptable.

Because these sources of interference are so very low frequency in nature, they are often unnoticeable when monitoring on nearfields, such as the Yamaha NS10s found in most studios. So it's a wise move to listen to the microphone signal at a decent level on large, main monitors to begin with. Once you're sure there are no bumps or rumbles taking place, then you can relax back into using the (much less tiring) nearfields to continue the session.

To deal with ultra-low frequency noise using an equaliser, it is almost always a good idea to switch in the low frequency roll-off filter that most modern mixing desks provide. If your desk doesn't have adequate filters, then make sure you get a quality microphone with one built-in. This will not detrimentally affect your recording, as most ultra-low frequency noise is well outside of any frequency range that is musically useful for the instrument or person being recorded. The exception is obviously when you are using a microphone to record a very low-frequency sound, such as a bass guitar, cello, or other low-frequency instrument, where keeping ultra-low frequencies is paramount.

Interference

Don't forget, however, that the top end needs attention, too - there's been many a good take spoiled by subtle radio interference from nearby sources. When recording electric piano, for example, try filtering off the top end until the sound gets quite muffled, and then slowly open it out again until the basic sound remains unaffected by the filtering. Of course, it is possible to fix it in the mix, but that means putting up with unsatisfactory monitor mixes until the main mixdown takes place.

Finally, if you're the very cautious type and you have a mixer with high and low pass filters, it can be a good idea to crop off the unwanted parts of the sound that are theoretically outside that instrument's frequency range. Like we said, if you're really cautious...

Mains hum

Mains hum should be removed using a physical solution rather than resorting to EQ. This is rarely just the nice, clean 50Hz hum that you can hear clearly at the low end of the spectrum. More often than not, the hum will include many harmonics reaching right up into the audio spectrum. This is especially the case when recording electric guitars.

The usual candidates for introducing mains hum are: having mains cables too close to instrument or mic cables, fluorescent lights and dimmers, computer monitors, and wall-warts. Keeping unbalanced cables as short as possible goes a long way to removing hum, as does the use of guitar DI boxes using balanced mic leads, in preference to using long, standard guitar cables.

Removing hiss

With multitrack recordings, hiss can build up over the individual tracks, but these can easily be cleaned up to a satisfactory level. Obvious places to start are with the bass drum, bass guitar, electric piano and noisy guitar pick-ups. These instruments have a lot of energy in the high frequency range that you don't want to lose, but in practice most of the energy is well below 8kHz, the frequency above which noise becomes particularly offensive. So under these circumstances use a low-pass filter to damp as much of the top end as possible. With other instruments, it's usually best to leave well enough alone. A little bit of hiss isn't too objectionable - as long as the worst culprits are taken care of, the rest can be tackled with noise gates.

Noise spill

The ability to physically remove offending noise spill from live band recordings is an art in itself, and usually only comes with many years experience of all the different microphones that you use and, in particular, a good knowledge of the characteristics of the room you are recording in. That experience teaches you when to physically shift things in the room about, and when to resort to some careful EQ.

So don't work too hard at removing spill physically from sound sources - it's a case of diminishing returns. If you over-damp everything in the room, your recording will be dull and lifeless. If you put up too many acoustic screens, the musicians will feel disconnected from each other and a poor performance could be the result.

There is also a much more serious problem: if you move the band members too far apart, you will introduce a time delay between all of the microphones, and the spill from each instrument will create slapback echoes. This will result in a very echoey sound, with the drum kit sounding as if it is very far away, and no amount of equalisation will save you.

Damping unwanted harmonics

In most cases during tracklaying, you want the sound you record to feel smooth across the entire sound spectrum. However, when recording live instrument sources, one of the most common problems encountered is the sound of an unnatural ringing in the instrument, produced by unwanted harmonics. In some cases, the ringing is so loud that it can send the level meter shooting way into the red when it happens.

While drums (and snares, in particular) are notorious for producing these unwanted harmonics, they are not the only instruments that can suffer. Some guitars have particular notes that seem to leap out of the mix at you, and certain bass notes can shake the room. Additionally, harmonics can originate not just from the instrument itself, but also from the room you record in, and - in the case of electric guitars, or Hammond organs with Leslie cabinets - from natural resonances in the speaker cabinets themselves.

How well you can deal with these problems depends to a large degree on what kind of equaliser you have available. What you are looking for is a sweep or parametric equaliser with a very, very narrow bandwidth. The EQ sections in budget mixing desks often do not have the ability to get a bandwidth tight enough to do the job, and you might have to resort to an outboard equaliser that gives you full control over the bandwidth.

The technique for finding and isolating harmonics using an equaliser is relatively simple. First, turn down the monitor level so it's quite quiet. What you are about to do can not only hurt your ears, it can also damage speakers if they are turned up too loud. Set the EQ on a very narrow bandwidth, and turn the gain up so you have a boost of about 6-12dB. Then, using the frequency control on the EQ, sweep the equaliser through the frequency range around where you suspect the troublesome harmonics are. You'll know when you've hit the right spot - the offending harmonic will leap out at you at full blast and be immediately recognisable as the source of the problem (that's why you need to turn the monitor speakers down).

Now that you've isolated the offending frequency, turn down the gain control to give you a cut of about 6dB. Now you can safely return the monitor speakers to a sensible listening level. Once you're at this stage, you can listen at a good monitoring level and decide how much cut is actually required. Finally, play with the bandwidth control until you get the most natural, smooth sound. By a careful balance of frequency, tight bandwidth and gain, you should be able to get the offending harmonic ringing down to a level where it is either acceptable, or gone completely.
And don't assume that you will only ever encounter just one harmonic problem on a particular instrument at any one time. You might well have two separate problems to contend with - and that's why it's always worthwhile having at least one powerful equaliser around that has more capabilities than the one built into your console.

As well as removing unwanted harmonics, a very narrow-bandwidth EQ can be used to generate harmonics that weren't there in the first place - what you will actually hear is the sound of the equaliser itself ringing. This technique can be used to good effect when, for example, recording a bass drum. A narrow bandwidth boost at 3-4kHz can work wonders in bringing a powerful kick into an otherwise dull-sounding drum.

Flattening frequency response

When close-miking sound sources such as drums, the microphones are usually set to a cardioid response pattern, either to hone in on the sound source, or because the dynamic mics used to record drums are usually non-adjustable. The problem that results is that cardioid microphones used at close range exhibit a phenomena known as 'proximity effect.' What happens is that the bass response goes sky-high and the sound becomes very stodgy - no matter what instrument you are recording. The only way to prevent it at source is to either move the microphone further away or to change the microphone pickup pattern to omni-directional.
In the case of recording drums, usually neither one of these solutions is desirable...

So when recording and mixing real drums it's a good idea to roll off a fair bit of the bass, in this case to correct the sound of the microphone, with the effect of getting the recorded sound back to what it actually sounds like in the first place. Take the time to go out into the room, listen to how the drums really sound, and try and duplicate that sound in the control room.

A careful combination of low frequency roll-off and low frequency shelving EQ is required to flatten the frequency response.
If you don't have an equaliser with a shelf response, then use a sweep or parametric EQ on the low end, provided the bandwidth is very wide (the opposite of the setting used to remove harmonics). Once you've got to that stage, you can perhaps extend the operation by a few tweaks to polish the basic sound. If, on the other hand, you try creating a drum sound from scratch - without even going into the room to listen to what the kit actually sounds like - then you may be working on that drum sound for a long, painful time.

Sweetening the sound

Okay - so you've followed the techniques above in order to get a basically clean recording. At this point, you may be tempted to go crazy with the EQ trying to create a sound. This type of creative EQ'ing is really best avoided when tracklaying. Until you've finished recording the entire track, it isn't possible to hear how the set of instrumentation you're working on will fit into the complete recording.

For this reason, you should be as conservative as possible when sweetening the sound during recording, and make only minor enhancements. Use a broad bandwidth and restrict yourself to subtle raising and lowering of the top, bottom, or mid-range. There are some basic rules to observe when doing this (unless the part is sequenced and easily reconstructed using readily-available equipment - in which case you have the flexibility to do as you choose as you record)...

Don't do anything that rolls off the frequency response at either end of the spectrum if you're not 100% sure you'll want to do this in the final mix. Once you've rolled off the ends of the frequency response using low-pass or high-pass filters, it is usually impossible to get it back later on. Instead, approximate the desired effect using monitoring EQ (if you have it), and leave the final, destructive roll-off equalisation until the mixing stage.

Likewise, avoid filtering off too much top end. On an analogue recorder - even a pro-quality 2" machine with noise reduction - you can introduce a lot of noise during mixdown by trying to put back top end that was rolled off too much when recording.

Analogue tapes tend to lose top end naturally during the wear and tear of music production anyway, so you need to protect the top end as much as possible. If you are recording instruments such as sharp-picked or rhythm guitars, it can be worthwhile to add just a little extra brightness at about 4-8kHz, to compensate for the loss in top end that the analogue tape will have by the time you come to mix it.

On a digital machine, you have much more flexibility. Even so, it's still not a good idea to roll off too much top on anything during the recording stage, because many project studio digital recording systems have relatively noisy D-A converters on them, and the hiss will be noticeable when boosting the top end during mixdown. So, as a general rule, don't overdo the 'sweetening EQ' during recording. In the rushed environment of tracklaying, it's very easy to get it wrong, with the result that the monitor mixes will suffer until you get a chance to do a proper mix. And even when you get to the final mix stage, it can be hard to undo the mistake while still keeping a natural sound.

Naturally, you want to get the sound a good way towards how you expect things to be in the final mix, but it is a difficult balance between getting a workable result and boxing yourself into a corner. Doing anything too severe when recording restricts your options for doing different kinds of remixing and experimentation later on.

Finally

All of the above techniques can, and should, be used to good effect while tracklaying, for two reasons: firstly, to ensure the cleanest possible signal is being recorded, and, secondly, to free up as many resources for the all-important mixdown session, where EQ can be put to much better use as a creative, rather than a correctional, tool. While this attention to detail can be time-consuming, the process of filtering out unwanted sound, damping harmonics and flattening an unnatural frequency response is a fact of recording life, but one that can reap huge rewards in terms of the quality of your final mixes.

When to apply EQ: recording or playback?

One of the main considerations when applying equalisation - or any other kind of signal processing - is whether to apply it during recording or playback. It can be agonising trying to decide which. There are three basic considerations: first, is the EQ in any way destructive to the sound? None of the techniques described in Part One of this article can be considered destructive to sound - quite the opposite, in fact. All of the techniques are designed to create a pure, clean sound.

Second, will it take time to set it up in future? In the case of hardware mixers, the answer is obviously 'yes' - and it seems pointless to waste time at the beginning of each subsequent session redoing all those clean-up tasks that can be done just once, at the start.

And finally, will you want to use the EQ module for something else later on? The answer, again, is almost certainly 'yes'. When it comes to mixing - a subject we will deal with in detail in the next issue - you will want to use the equaliser to do more creative things to the sound, so there is little point tying it up doing basic clean-up tasks that you can do while recording.

On a desktop computer system, you might be forgiven for thinking that you can leave all EQ'ing until mixdown. After all, the EQ settings will be automatically recalled next time you reload the project file. But there are three reasons why this is not a good idea: first, a bass-heavy, close-miked sound, or a sound that contains loud unwanted harmonics, eats into the valuable headroom of your soundcard. By the time you've filtered these undesirables out, the signal level may have dropped substantially and the signal quality will suffer. This is less of an issue with the new generation of 24-bit soundcards, but it's a serious consideration with 16-bit cards.

It's far better to get a good signal out of a quality mic amp with an excellent analogue equaliser, and capture that sound on your soundcard, than to pump any old lo-fi sound in and try fixing it later in software.
Second, having lots of equalisers running at once on your desktop system eats into valuable CPU resources. It is much better to record a great sound going into your computer and use CPU resources for more important things, such as effects or more tracks.

Finally - as is also the case with hardware mixing consoles, when it comes to mixdown, you will want to use the EQ on the channel for new, creative tasks, not for correcting something you could have recorded properly in the first place.

Need more EQ?

You might have more sources of specialised equalisation available to you than you think - even if you don't have dedicated outboard equalisers. Most modern digital outboard equipment is exceptionally flexible. For example, a Yamaha A-series sampler can be used as a sophisticated EQ when recording live sound sources - even at the same time as you are using it for sequenced sample playback. Similarly, some outboard processors can be pressed into service - for example, TC Electronic's M's;One has a fully-parametric EQ and Drawmer's DS 201 comes with hi and lo-pass filters.

EQ: the downside

EQ can damage sound, as well as enhance it - remember that EQ affects more than just frequencies. An unfortunate side-effect of EQ is that it also affects the subtle timing relationships between the different frequencies, meaning the sound is no longer 'phase-coherent' across the audio spectrum after adjustment. When people complained about the harsh sound of early CD players, scientists soon realised that the human ear is far more sensitive to this timing information than was originally thought.
Certain types of EQ also introduce subtle ringing artefacts into the sound.

If you over-rely on EQ to achieve the sound that you want - especially the EQ that's built into your desk - these factors can conspire to create a mix that sounds cheap and unnatural and, worse still, gives people a headache. If, on long mixing sessions, you find that you're getting frequent, painful headaches and you are not otherwise ill, there's a good chance that you have been over-EQ'ing the mid and top frequencies of important elements of the mix.

Despite these considerations, if you attend a recording or mixing session, even with people who claim they don't use EQ, you will still probably find that the EQ is switched on within almost every channel of the desk.

Types of EQ

1. Filters

Simple filters come in two styles: either a single button for rolling off the bottom end or two rotary controls marked LF and HF. These control how the sound is 'trimmed away' at either end of the audio spectrum, although usually the roll-off is preset and varies with each manufacturer.

2. Shelf

These are capable of both boosting and cutting the sound starting at a given frequency. There's usually one each for top and bottom, with the low frequency shelf EQ working at around 80 to 150Hz, while the high frequency shelf EQ will cover around 8 to 12kHz. Unlike roll-off filters, the amount of boost or cut remains uniform to the ends of the spectrum, giving a level gain change to the affected frequencies.

3. Sweep

Using a sweep EQ allows for frequency selection, with the cut or boost affecting only the area surrounding the specified frequency. On simpler systems it isn't usually possible to control the width of the sonic 'area' affected, and this width varies depending on the manufacturer. Some manufacturers like to keep the area fairly broad, as this is more musical, but others prefer to keep it narrow, as this is more useful for correcting harmonic problems.

4. Semi-parametric

A sweep EQ on its own is of limited use, so these sometimes come fitted with a switch or button that can change the bandwidth covered, giving a choice of narrow or wide response. The whole assembly is often named a semi-parametric EQ.

5. Fully parametric

Top-of-the-range mixing desks are fitted with fully parametric equalisation, whereby you control the frequency, the gain and the bandwidth of the EQ. Often, four of these units are packed together, and a switch on both the first and last unit allows them to be optionally used as shelf high and low frequency EQs, respectively.

6. Graphic

Graphic equalisers allow you to adjust fixed frequencies
over the entire spectrum. These are best employed where a large number of subtle adjustments to the signal are needed - for equalisation of a control room's main monitors, for instance, or for final equalisation of a finished mix while mastering.

7. Passive and Valve

With many equalisers, audible 'ringing' is introduced into the signal, due to the electronic feedback techniques employed. Alternatively, passive EQ cuts the sound across the whole spectrum. In this way, when you boost a signal, you're not really boosting it - the signal is just passing through the passive circuitry unhindered. Valve EQs often work in the same way. Their smoothness often has little to do with the valves; it's usually down to the fact that the circuitry is passive, not active.

8. Software

The beauty of recording on computer-based systems is that all the above-mentioned EQs can be relatively easily modelled or simulated in software. The benefit of having quality EQ plug-ins is that these can be used on as many tracks as you wish, an obvious benefit over a hardware EQ that can only be used over one sound source at a time.

Part II

Many engineers and producers will tell you that each individual song should be taken on its own merits and treated as a unique entity when it comes to mixing. However, they will still have a repertoire of general techniques and more specific EQ tweaks that work for particular instruments time and again. What we are looking at here are not tweaks for specific instruments per se, (see the Tips of the Trade boxes on pages 20, 21 and 23 for these) but more of an overall view of how EQ can be used to pull the mix together.

Several techniques are presented separately throughout this article. In practice, they tend to interact with each other, and when mixing it is quite possible that you'll go through each of them several times, making finer and finer adjustments until the ultimate mix has been achieved.

Sound enhancement

EQ can be used in a creative way to enhance a sound by bringing out and emphasising some of its natural character. Most musically-useful sounds can be described as containing the following four basic frequency components: subharmonics, fundamental notes, upper harmonics and high harmonics.

Generally speaking, when using EQ for general sound enhancement, you are normally staying well away from the fundamental note range where the instrument's notes actually lie. This range is usually quite narrow and low anyway: for example the 'fundamental' part of the A above middle C is only 440Hz.

What we are talking about here is boosting or cutting frequencies in the other three bands to produce the sort of generalised effects that are usually described by vague emotive language. For example, adjusting the subharmonics can make a sound warmer or colder. A sound can be made to seem harsher or softer without affecting its volume level by adjusting its upper harmonics, while the high harmonics can affect the amount of sparkle, dazzle, sheen or air in a sound.

Most of the interesting low and high harmonics that can be excited by careful EQ'ing are usually either much higher than the highest note the instrument plays, or lower than the lowest. But tweaking them rarely results in the instrument leaping out of the mix in its high or low registers - the effect is more subtle. If problems do occur, with the instrument seemingly getting louder as it approaches high or low notes, this can be corrected, without compromising the overall effect, with a bit of judicious 'counter-EQ' using a narrow bandwidth on the edges of the fundamental note range.

Sonic microscope

Before you go about equalising the sound in this way, it is always worthwhile to begin by using the EQ as a kind of 'sonic microscope' to carefully examine the sound and hear just what is present in each frequency range. To do this, use a medium bandwidth EQ set to a moderate amount of gain and sweep through the entire frequency band, listening carefully to what you find. Also, sweep through the entire band with a medium amount of cut as well, and listen to how that changes the sound. At this point, you're not using the EQ as a tool to change the sound at all - you are just exploring what you've got to work with.

This kind of sonic exploration of instruments is, unfortunately, much harder to do using a 'soft' (screen-based) control interface than it is when using real knobs on a traditional physical console control surface. If you are using a computer-based recording and editing package, you may find it much quicker and more intuitive to use some kind of tactile MIDI controller (like Kenton's Control Freak, GMEDIA's Phat Boy or Peavey's PC1600 X) rather than a mouse to control the EQ.

With this method of exploring your sounds, it is possible to locate the main sonic component that characterises any particular instrument. You should be able to determine where the interesting harmonics are, and thus find yourself better-equipped to decide whether you need to boost them, cut them, or perhaps even leave the sound alone completely.
In some instances, using the EQ as a listening tool in this manner could lead you to decide that the sound might benefit from something other than EQ. For example, you might discover that an instrument (say, a guitar) potentially has a lot of attack that isn't immediately apparent in the un-EQ'd version. To bring out that attack, you may decide to use some compression with a slow attack setting to accentuate the 'front end' of the guitar, rather than use EQ, which might result in an artificial sound if overdone.

When using EQ, there is always a danger of overdoing it - to the inexperienced, the way that a freshly-applied EQ can lift the component that characterises a particular instrument can seem quite exciting. So as a rule, for instruments that are playing independent musical parts, try to accentuate the voice of each instrument only so it retains its own place in the mix, while still being sufficiently big to fill that space. Don't over-characterise an instrument unless you intend to place it far back in the mix and you're already finding that it becomes indistinct at the required volume.

Distance placement

It's a common-enough analogy to liken a mix to a painting. The left-to-right perspective is created by panning the instruments, but what of the front-to-back perspective? Which elements of the sound are in the foreground and which are perceived as being further back is dependent on a number of interrelated factors, one of which is EQ.

Positioning and distance in the mix can be created with the use of reverb and/or delay, but used by themselves, these effects only go part of the way towards creating a natural sense of depth, and can sometimes result in a messy sound. Combine them with judicious use of EQ, however, and the possibilities are greatly increased. EQ techniques for creating distance are based on the way that sound disperses in nature and the way the human ear works. As sound travels through air, its frequencies are absorbed over distance - especially the high frequencies, which decay much quicker than the lower ones, so nearer sounds will tend to have a higher treble content than distant ones.

For bass frequencies, there is the proximity effect to contend with. This is the phenomenon exhibited by most directional microphones, whereby the lower frequencies tend to be over-emphasised when a sound source is very close to a mic (get a vocalist to sing directly into your ear and the same thing occurs).

These phenomena can be exploited when mixing by either boosting or cutting the high and low EQ controls on your mixing desk. Of the two, it is probably cutting that is the most useful tool when mixing. By rolling off some bass and top end, you can push a sound back into the mix and make it sound further away. This is very effective when used in
conjunction with reverb.

The opposite effect - bringing instruments, and especially vocals, forward - can be achieved by boosting their high and low frequencies to make them sound closer than they really are. It's important not to go too OTT with the boosts, however, as this could lead to mixes that sound a little too 'hi-fi' and perhaps lacking in mid-range energy and excitement.
To create a 'big' mix, you may be tempted to make each part or instrument sound big in its own right, but big only seems big when other things seem small. It is the light and shade, the contrast of one part against another, that can make a mix something special. Some instruments may be left to sound natural, some, such as vocals, can be brought forward with a little top and bottom-end boost, and some can be thinned out with cuts to sit them further back.

Use this technique hand-in-hand with some appropriate reverb (and of course the relative volume levels of sounds) and you can put the illusion of distance into your mix, making it sound significantly larger overall.

Creating room in the mix

Let's consider that you have recorded an arrangement with loads of instruments all playing parts that fit together well, but with all the faders up, the mix still sounds a little cluttered, perhaps with some instruments masking or obscuring others. How do you create a little more room in the mix for each instrument to breathe and be heard, without resorting to the kind of serious editing that involves cutting out or muting some of the instruments?

With creative use of EQ, you can carve out some room, pushing some instruments out of the way to make space for others. This method was frequently utilised at Tamla Motown, usually to allow vocals to come through clearly. The idea is to use subtractive EQ to remove frequencies from certain instruments that may be clashing with other sounds in the mix. This can take the form of EQ'ing individual instruments, or alternatively, a set of instruments can be subgrouped and EQ'd collectively.

This technique could be viewed as being somewhat brutal, but there will be elements in some instruments' sounds that serve no purpose other than to muddy up a mix, even though they may be a constituent part of the normal sound of the instrument. The boom of an acoustic guitar, for instance, can add unnecessary clutter in the frequency range where the bass and kick drum should be. Indeed, if you were to use a large amount of subtractive EQ on a particular instrument and then listen to that instrument solo'd, it might sound particularly horrible, as if some of its character had been taken away. However, that is largely irrelevant, as once in a mix, any instrument is a constituent part of that mix and should be listened to in that context. Something that might sound quite nasty when solo'd could sound great in the mix. In the case of the acoustic guitar, for example, we may only want to hear its top end anyway.
For instruments that are playing the same musical part together, the opposite might apply. It is often a mistake to make them sound independent; instead, try to make them combine into one single, bigger sound - even if the instruments used are quite different. Separating them can, in any case, be difficult, as the ear will subconsciously try to merge them, so there's little point using EQ to make the two parts distinct when, from a musical perspective, they are not.

For example, think of George Benson's distinctive scat vocals that accompany some of his guitar solos, and how the vocal and guitar blend together to form a bizarre new guitar sound. Similarly, mixing synth sounds with live strings can be much more effective if you try and combine them to create a new type of unusual string sound, rather than leaving it sounding like a silly little synth playing over a massive orchestra.

Auto mix levelling

When mixing, on some instruments, certain notes will jump out at specific times and be over-prominent, or alternatively may seem subdued and almost disappear. One way to overcome this is by adjusting the level of the sound every time that the offending frequency occurs. Automated faders could sort this out, but it's not everybody that has automated faders, and for those that do, it could take hours to get all the right levels programmed in at exactly the right places.

The other solution is to use EQ, which can produce better sonic results, and has the advantage of being much quicker to set up. What we are talking about is playing with the EQ at very specific points in the middle of the instrument's melodic range, which could cover a series of notes or even a single note.

As a starting point, use your ears to track down the source of the problem, by finding the frequency that causes the instrument to jump out or disappear. Usually, this will occur in the same sections of the song, where the same region of the instrument's note range is played. Using the 'sonic microscope' technique (described earlier) of boosting and sweeping the range, the specific frequency range where the problem occurs can be found.

Once you've identified the offending frequency, there are two ways to deal with it: by using EQ by itself, or by using EQ in combination with compression. Using EQ with a fairly narrow bandwidth, the frequencies in the problem area can be cut (or boosted, if the problem is one of the instrument disappearing) in that specific part of the song to get the balance right. Now, this means that those frequencies will be cut (or boosted) throughout the song, but often in these circumstances, the EQ tweak will actually work throughout the song as if the instrument has sorted itself out. Carefully check the levels in the rest of the song to make sure.

The other way to solve this problem is to use frequency-conscious compression, so that whenever the offending frequencies occur, the compressor kicks in and pulls down the gain. To use this technique, you need a compressor with external access to its sidechain. Feed the instrument sound through the compressor as normal, but connect an EQ unit (preferably a graphic) into the sidechain.

The idea is to boost the offending frequency range on the EQ, which will make the compressor more sensitive to those frequencies and compress harder when it 'hears' them. The setting of the compressor's release control is crucial here - set it so the compression stops and the sound reverts back to its previous level as soon as the offending section or note finishes.

Gelling the mix

So far, we have been discussing EQ in terms of individual sounds in the mix. But even if you've got to the point where all the individual sounds have their place in the mix and can be heard without being over-prominent, you may not yet have a great mix. You need to consider the overall impact of the mix as a whole, and look at specific areas of sound/frequency ranges or specific groupings of instruments. To this end, let's concentrate on two very important aspects: the rhythmic pulse and the top end.

With so much music being heavily rhythm-orientated, arguably the most critical aspect of a track is the pulse of the rhythm. This gives a track a lot of its energy, and EQ can be used to emphasise it. This does not have to mean a bass-heavy mix, but the relentless impact of the rhythm must be clearly felt in your body as you listen to the mix.

The primary contributors to the rhythm are obviously the drums and bass, although they are not solely responsible. The rhythm of the other instruments, such as piano and guitars, can play an important part in the overall mix. Unfortunately, there isn't any special formula to get the rhythm happening - it is likely to be different in every song you will record. You just need to be aware that a rhythmic pulse is there, and figure out which sonic components of which instruments are making the important contributions. This does take a fair amount of experimentation.
Rhythm is a product of the downbeat (usually the kick drum) and the offbeat (which is created substantially by the snare). The alternate push/pull of a song is the defining essence of its rhythm, and if you can get this across clearly, then people will get up onto the dance floor, or at least start tapping their feet when the record is played.

As a starting point for mainstream pop, the downbeat in a song should genuinely feel (at loud volume) like it physically hits you in the midriff or below, while the offbeat should hit you in the chest or higher. Of course, this varies with the style of music: in reggae, the downbeat is almost subsonic in nature, and in drum'n'bass, the offbeat is almost non-existent; with the snare being little more than a splattering percussive effect.
In many cases though, the offbeat is just as important as the downbeat, and other instruments can contribute significantly to the effect - look for syncopated beats that deserve accentuating in order to work with the snare. Rhythm guitars are prime contenders, especially in reggae music.

Take it to the top

The top end of a final mix always needs a great deal of careful attention. A subdued top end can sound unengaging and amateurish, while a good top end can make a track sound professionally polished and really shout 'Quality Production'. So what are the top end elements we should be looking at?

First off, cymbals add a certain amount of sizzle, and percussion instruments like shakers and tambourines can contribute in a similar area. Other contributors to the top end include vocals - not just the lead but also the backing - and don't forget the vocal reverb.

Acoustic guitars are also up there, and can add a nice silky sheen that that can be heard over the top of the mix, even on the crappiest of transistor radios. So the top end of a mix does warrant special consideration, but it has to be approached carefully, as it is easy to over-egg the pudding. Overdo the top end while monitoring at reasonably loud levels and your ears will grow tired very quickly and become somewhat immune to treble frequencies, causing you to pile on yet more top end to compensate - a vicious circle.

It is not at all uncommon to listen to what sounded like a wonderfully-balanced mix the night before and discover, in the cold light of day, that it sounds dreadfully tinny. A visual check of the desk will probably reveal that all the HF controls have been cranked up. The solution? Reduce the amount of HF that you gave each individual channel previously, or EQ the mix as a whole using a high-quality stereo EQ.

And finally

EQ is one of the most fundamental tools used in the entire recording process, and is probably the most versatile piece of equipment to be found in any studio. Hopefully, as you've worked your way through this two-part article, you'll have seen how EQ is not just a device for playing with the sound and changing it into something that wasn't there in the first place. Of course, many producers use it this way, but don't forget the original applications for which the device was invented: removing unwanted background sounds and leakage from other instruments, correcting for mic placement and pickup pattern and, as seen in this instalment, a creative tool at mixdown.

The techniques listed here should be regarded as food for thought to be considered when starting your mix, but there are no set rules, so don't forget to experiment. Combining some of these techniques with the use of compression, panning, effects and level should see you well on the way to some happening mixes. Happy polishing!

Faster pussycat

Generally, when using EQ, try and work quickly. Don't let yourself get bogged down spending a long time on any one particular sound. If something is not working, move on and come back to it later, as other changes you make further along in the process could solve the problem anyway.

Remember that it is not the sound in isolation that matters, but how the sound is perceived as part of the final mix. The chances are that after working on a sound in isolation, when you place it into the mix along with everything else, a lot of what you've done may not be audible and may need changing anyway - to some extent - for the overall effect you desire to be heard properly in the final mix. There is nothing wrong with going back and re-doing some EQ that sounds wrong in the context of changes made further up the line - it's all part of the interactive process. Be flexible.

Also, remember to use your ears. There is no point EQ'ing just for the sake of it. Listen carefully before reaching for those knobs - just because you have EQ it doesn't mean you have to use it. Some instruments will work absolutely beautifully in the mix with no EQ at all, so make sure you know that any adjustments you are about to make serve a genuine purpose for the instrument in question.

Listen on the flattest set of speakers you have, and at different volumes - the perceived levels of different frequencies will change at different volumes. Take as many breaks as you can from continuous listening, and compare your mix to commercial CDs that you know have a good sound.

Picture this

Imagine placing the various elements of your mix inside a three-dimensional box. The height represents the frequency range, and the width represents the stereo image (or left and right panning), while the depth is dependent on the amount of effects and level you add (or how wet or loud the sound is - the wetter the sound, the further away it becomes). All these factors need to be considered during mixing: space and clarity is the key to a good mix.

For example, allowing a simple guitar lick to be heard can involve a small pan to the left or right, as there are usually lots of things fighting for space in the centre. Bass sounds are usually the exception, as these should usually be left dry and in the centre: as bass is omni-directional, panning adds no benefit (and is certainly frowned upon by cutting engineers when pressing vinyl!).

The diagram on the right is not the whole picture, of course, as all of the above factors of placement are affected by level (or gain), which controls which instrument sits 'on top'. Of course, the above can be disregarded if you're mixing in 5.1 surround - that's a whole different ball game...

Frequency ranges: a few pointers

50Hz
This is the super low-end range that can make your internal organs dance around when you're in a club with a good sub bass system cranked up - we love it! Use it to beef up bass drums. Get rid of anything around here on vocal tracks (often the sound of 'pops').

70 to 100Hz
This is nice added to basslines and bass drums for that sub sound so essential in dub records. Again, this is a rolloff frequency for vocals. Note: many sources of sub bass end up cancelling each other out, as bass frequencies are very susceptible to phase problems. For example, if your bass drum disappears now and again in the mix, it's because something else is hitting exactly the same frequency. In other words, adding more bass to things can often lead to a bass loss in your mix.

200 to 400Hz
Use to either remove or add that 'woody' effect to/from a snare, or to either warm up or remove that muddy sound from vocals. Boost here to fill out guitars, cut to thin out hi-percussion parts or cymbals.

400 to 800Hz
Use these frequencies to adjust the clarity of the bass tone or warm up that 'box' sound of toms. Again, boost or cut here to thicken/thin out guitars. Reducing some of these frequencies can help tighten up the overall bass sound of a mix.

800 to 1kHz
I use this for vocal thickening of a different nature to the low-end stuff mentioned earlier. Boosting at 1K can add to the 'knocky' sound of
bass drums, especially useful in dance music.

1 to 3kHz
Okay, now we're getting into the hard stuff. Boost around 1.5 to 2.5k to add edge to guitars and basslines. Cut some of the upper 2-3k range to help smooth out vocals, especially those vocals that seem to cut your head off when listening at high volume - unless you're one of those sadistic people (like Adrian Sherwood!) that like that. Boosting here can also add edge to pianos and vocals. This is a 'hard' range that is not pleasant-sounding, but it can help instruments stand out in the mix.

3 to 6kHz
Boost some of these frequencies for the ideal 'plucky finger' bass sound; cut at the 3k range for less of that hard sound on vocals. To soften sounds (not everything should be bright) cut the upper range to dull off certain parts. Boosting at 6k can be a good upper point for adding clarity to vocals, and nice for distorted guitars.

6 to 10kHz
Boost here for sweetening vocals. As you go up in frequency, you add more air, getting that breathy sound. Boosting around here will add crispness to acoustic guitars (but be careful not to overdo it). Percussion and cymbals all benefit from boosting some of these frequencies: boost for the ring of a snare and the top edge of a bass drum (yep, a bass drum), and to add edge to synth sounds and strings.

10 to 16kHz
Boost here for even more of that breathy sound on vocals, and to add that extra zing to cymbals and percussion. Cut here to reduce noise on sounds that aren't bright. Boost for more sparkle on pad sounds and the like, but only if the frequencies are there: more often than not you'll just be adding noise!

A final note

Some engineers claim it is better to cut then to boost when using EQ, but personally, on the hundreds of records I have mixed, I have never really followed this theory. At the end of the day, you do what you think sounds right to make the mix work - when working on Nine Inch Nails tracks, for example, I'm hardly gonna think 'I better not be too outrageous with the EQ!'. Sometimes, you might be better off using processors that brighten sounds, as some EQ units can make things sound hard and brittle when adding top end. Keep everything organised on your desk or in your computer so nothing is adding to the mix that shouldn't be, and keep the levels as high as possible without clipping. And above all, have fun!

Tips of the trade: vocals

In Harsh irritating edge due to the inherent characteristics of a particular voice (or a nasty-sounding mic) can usually be cured with a narrow bandwidth cut somewhere in the 2.5kHz to 4kHz range. A gentle shelving boost somewhere above 6kHz can open up the sound, and there will be little useful in the real bottom end, so use a high-pass filter to roll off anything below 60Hz.

To add brightness to vocals without making them sound harsh, try a little gain at around 6k upwards with a nice wide band, and sweep the frequency range until you like what you hear. Then, for a smoother sound, take out some mid range by removing a small band (Q) around the 1-2kHz range. To boost the bass, try a narrow Q somewhere from the low mids right down to 200Hz - the exact spot will be dependent on the source sound.

For that radio effect on vocals, roll off a little top and lot of bottom, then add a lot of gain in the mids - around 9dB of 1.5k. Then, for some added extra 'phone' quality, compress very hard. Any extra generated noise generated is usually nice - try turning up the line gain to overload the desk channel.

Remember that EQ is not just for the source sound, but also for any effects it is sent to. A nice vocal delay spin can be created by sending the vocal to another channel that is 'floated' from the mix (not in the mix). Feed in the radio effect described above, then send it to a delay unit. You will get a nice thinned-out delay effect for smooth- sounding vocals.

Tips of the trade

Muddy sound is a major problem that can benefit from an EQ cut. Muddiness can occur in many instruments, but is particularly noticeable with kick drums and acoustic guitars. Try cutting somewhere in the region of 300Hz (although anywhere from 100Hz to 800Hz could be appropriate) to thin out the sound, but be careful not to lose too much of the sound's 'body' that is present in the same frequency band.

With a hi-hat, rolling off all the bottom end (say, below 600Hz) will help clarity, while a top-end boost at around 10kHz will add a bit of sizzle. 'Clangy' frequencies will probably be in the upper mids - try a cut between 1kHz and 4kHz.

If vocals and guitar are clashing, try subtractive EQ, cutting the guitar between 1kHz and 5kHz to let the vocal through. Then, to compensate for its loss of mids (and so you can hear it without masking the vocal) boost the guitar in the bottom end somewhere between 100Hz and 250Hz and in the top at around 10kHz and 12kHz.

Add some extra sparkle to an acoustic guitar by adding a little 10kHz boost.
A kick drum may need to lose some flab around 300Hz, but might also benefit from some low-end boost between 40Hz and 80Hz. Try a boost around 4kHz to 6kHz for more attack, or roll it off if you want less.

Digital and analogue EQ

It may seem like a strange concept, but different EQ units have different sounds. The individual components and design of an EQ unit all have a different effect on the way an incoming audio signal sounds when it is cut or boosted. That's why some units are so expensive and others are not, and sometimes you'll be better off not switching in the EQ on your budget analogue desk when recording to computer, but using a less noisy plug-in EQ instead. On the other hand, if you have a classy valve EQ, you might want to switch it in when recording, as it could add some extra warmth to the sound.

When it comes to large studio consoles, many engineers around the world favour Neve desks for recording and mixing because of their warm, smooth sound, while others favour SSLs, with their powerful, sharp EQs, for sculpting sound. When it comes to digital units - as many analogue purists will attest - these can give good results, but can incur certain quantisation errors if the levels are low.

Credits: Jezar Wakefield & Alan Branch from Intermusic

Did you reach this far? If you did, you probably know more about EQ then before :)

Jquake

zzzzbump

wow thats a lot of info ...wow... :clap:

Sweet, good info :lol:

a lot of stuff to work through here, thanks man