How to manage low, mid and high frequencies in the mix

The effective management of audio frequencies is one of the most important skills for the aspiring producer/engineer to focus on and, ultimately, master. In the broadest sense, the full intricacy of the frequency spectrum can be conveniently – and wholly legitimately, from a technical perspective – divided into low, medium and high ranges, and optimising the relationship between these using equalisation and other techniques is vital if you want to bring out the best in your mix in terms of clarity, depth, punch and overall professionalism.
 
Of course, every mix is its own singular entity, with individual and mixing demands to be met, but in this article, we’ll provide you with some very general pointers to help ensure that the three titular sonic strata are solidly in place.

Understanding the low, mid and high frequency ranges

When we talk about managing the lows, mids and highs in a mix, we simply mean making sure that all three primary frequency ranges are properly balanced, with none of them dominating the others or getting lost; and that instruments occupying the same frequency range at the same time don’t ‘mask’ (obscure) each other. Clearly, the ability to do this requires knowledge of what each of the three ranges actually comprises, content-wise, so here’s a quick breakdown:

• Low frequencies (20Hz-250Hz)

At the bottom of the spectrum, the low frequencies are where the weight, warmth and visceral impact of the mix reside, taking in bass instruments (guitar, upright or synth) and kick drums. Anything below around 60Hz is considered sub bass and needs to be very carefully controlled to prevent unnecessary consumption of headroom, which can play havoc with a mix.
If the low frequencies are too loud, the result will be a muddy, booming mix, lacking in presence and definition. Push those lows back too far, on the other hand, and your mix won’t have enough heft.

• Mid frequencies (250Hz-4kHz)

At the centre of the audible spectrum, the mid range is home to vocals, guitars, snare drums, lead synths, pianos, strings… the defining character of most main instruments, in a nutshell.
Too much mid range makes a mix boxy and awkward to listen to; while a mix lacking in mids will sound strangely hollow and fail to carry the song as well as it should, as its most aurally attention-grabbing elements are pulled to the back.

• High frequencies (4kHz-20kHz)

Less clearly demarcated in its instrumental occupation than the lows and mids, the high frequency range contributes brightness and presence, and is heavily involved in the sounds of hi-hats and other cymbals, hand percussion, vocals, and top instrumental notes. Too much volume in the high frequency range will be fatiguing on the ear; too little and the mix will sound dull, unexciting and amateurish.

Tools of the trade

Equalisation, or EQ, is the most powerful weapon in your frequency management arsenal, enabling the intuitive and precise cutting (lowering in volume) and boosting (increasing in volume) of targeted frequency bands. Your DAW will offer at least one versatile ‘channel EQ’ plugin, featuring a versatile combination of parametric and shelving bands, and low- and high-pass filters – everything you need to get your lows, mids and highs in order. The parametric bands are ideal for surgical notching of mid-range resonances, for example, and making shallow cuts and boosts anywhere within the spectrum; while the shelves give you the means by which to lift or lower the bass, and add high-frequency shimmer; and the filters are useful for doing away with noise and rumble. Here are some specific issues to address within each range:

• The low end

It’s often suggested that every non-bass sound in a mix should have a high-pass filter applied to it, for the purposes of eliminating the aforementioned headroom overload and maximising low end clarity – but that can actually do more harm than good if not handled extremely carefully, making individual instruments sound thin and sterile. For those parts that clearly have no business reaching down below 60Hz, however (vocals and guitars, most pertinently), it’s certainly a viable tactic. Beyond that, a low shelving EQ rolling down from around 100-150Hz is just the thing for calming down or boosting an overly exuberant or flaccid bottom end.

• The mid range

With so much going on in the psychoacoustically critical mid range, the reduction of ‘mud’ in the 250-500Hz band and ‘honkiness’ from 500Hz-2kHz can prove challenging, but a gentle, wide cut in the former and judicious narrow cuts in the latter should get you over the line. Also, try a small boost somewhere around 1-3kHz to enhance vocals and lead instruments – and we do mean small, as this is a particularly sensitive part of the mid range.

• The highs

Harshness and sibilance in cymbals and vocals are two of the main things to watch out for from around 5-8kHz, and can be dealt with using parametric EQ or a de-esser. On the additive side of things, boosting from 10kHz up with a shallow shelving band is almost always beneficially transformative, adding air and sheen, and opening the mix up nicely.

Alongside EQ, compression can also be helpful with frequency management, as flattening down an overly dynamic signal might have a significant impact on its spectral profile, especially with regard to sharp transients. Dynamic EQ plugins, which combine equalisation and compression/expansion, can be a real boon for suppressing irksome resonances and are well worth investigating, too. And sometimes all it takes to move one part out of the way of another for the purposes of unmasking is panning – just slide one a bit over to the left and the other a bit to the right, and if it works, check for mono compatibility before committing.

Monitoring: a crucial consideration

While your DAW will include more than enough in the way of EQ and other plugins to handle the management of low, mid and high frequencies with no further outlay required, there is one inescapable expenditure to negotiate if you’re serious about your mixing. No two ways about it: if your monitor speakers aren’t of high enough quality to accurately represent the full audible frequency spectrum, obviously you’ll struggle be balance the divisional ranges within it. So, don’t scrimp when it comes to investing in this all-important component of your studio. A sub woofer might also be something to think about, but don’t compromise on the spec of the main monitors just to make that happen if you’re wrangling a budget.