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Article from Making Music, January 1987

The varieties, the uses, the pros and the cons.

EQUALISATION is the fancy word to use in front of friends when you're playing with the bass and treble controls on the gramophone. "Oh, I'm just rolling off a few dBs at 16kHz where I find the sibilance on the vocal a little offensive — the top edge of the cymbals is a touch obtrusive anyway."

At the end of the 1960s 'middle' controls were added to the bass and treble, and from that time onwards it's been far more hip to say equalisation than tone control.

The most popular types of EQ nowadays (abbreviation is even hipper) may be referred to as shelving, bandpass, graphic, sweep and parametric. Anything with treble, middle and bass controls on it is likely to be using one of the first two techniques. They may 'shelve' off frequencies (like a cliff shelving down to the sea) or allow only a certain 'band' of frequencies to pass through.

Graphic equalisers will be recognised by having a row of anything between five and 31 sliders on the front. These can be arranged into very pretty patterns but it should be noted that, in general, the prettier the pattern — the worse the sound. So, when being visually hip with a graphic it's usually best to have it switched off.

Sweep and parametric equalisers may be very similar to each other in appearance but the trained observer will note that the parametric has an extra knob. If anyone asks, tell them it's the 'Q' control. If you choose to spout off about Q then you'd better read on in case your inquisitor is not yet satisfied.

Equalisation is all to do with turning up or down the gain at different frequencies. Turning all of them up at once is what the volume control does. We can hear things between frequencies from about 20Hz up to 20kHz. Treble and bass controls would split this range somewhere in the middle and affect just the top or bottom parts of the sound exclusively.

A graphic equaliser will alter the gain (boost or cut) at a series of fixed frequencies with a slider for each. A 31 band graphic has enough fixed points to cover the entire audible range from 20Hz to 20kHz at intervals of a third of an octave.

A sweep equaliser has one variable frequency control to select the precise point where the boosts or cuts should be made. In addition to this the parametric can decide how tightly to focus its attention. This is where the Q or bandwidth control comes in. A narrow Q pinpoints a precise frequency, whereas a wide Q will stretch out to affect a whole range of frequencies either side of it.

The question is often asked, "In order to be the most hip, which type of equaliser should I have?"

Graphics are very good for overall tailoring and lend themselves well to room or hall equalisation when placed before the power amp in recording or PA chains. In this way rogue resonances and standing waves can be countered by a little low frequency cut at the necessary points. Also the crispness and clarity at the top, which might otherwise get lost in the curtains, can be helped by a little high frequency boost. Graphic equalisers get extra Brownie points because the positions of their sliders give a visual impression of how they are affecting the sound.

For closer work on specific sounds, sweep equalisers offer a relatively simple solution. They are quick to use as you can hear the effect you are having as the frequency control is swept through to zero-in on the area requiring attention. A bass drum may have lost its slap (2-4kHz) and by increasing the gain and sweeping through the frequencies it may be re-discovered. The same bass drum may also be a bit flappy (300Hz) above its good thud (50-100Hz) area and this can be selectively scooped out. The fundamentals of the human voice occur within the relatively narrow range of 100 to 700Hz so the body of the voice is altered most at these frequencies. However, to give clarity and presence to a voice, a lift at around 5-7kHz is very handy. The crack of a snare drum is also enhanced around this frequency.

To really get down to the nitty gritty, a parametric EQ will allow for very precise pinpointing of troublesome or desirable spots. For instance, a mains hum can be sharply notched out. Although parametrics are extra hip in terms of their versatility, they are more expensive and slower to use than sweep EQ. So only go for them if you really want to impress.

A tip to be hip when recording is to try to do any large amounts of equalisation on sounds at source before they go on to tape as any boosting off tape will increase the level of tape noise. For cassette based multitracking, where tape noise can be a problem at the best of times, a simple form of noise reduction can be achieved by boosting the top of everything a little when recording and then reducing it again by the same amount when mixing. This should bring down any tape noise also present.

Another tip to would-be recordists when deciding which system to invest in is not to be too concerned about fancy equalisation on the mixer. When multitracking, often only one track is laid at a time so it makes sense to invest in one or two decent outboard equalisers to deal with the trickier jobs, rather than pay out for a fancier mixer where much of the gadgetry may be lying dormant for a large amount of the time.

Of course one of the hippest things you can do with EQ is not to use it. If you can get your thing sounding good at source then you've won. On the other hand, if adding a bit here and chopping a bit there improves matters then what the heck — give it a tweek!

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Publisher: Making Music - Track Record Publishing Ltd, Nexus Media Ltd.

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Making Music - Jan 1987


Previous article in this issue:

> Chord of the Month

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