Earlier i posted the interactive frequency chart It is a great tool for finding what instruments and what part of that instrument reside where in the spectrum. but there is a lot more to eq than knowing where the instruments are in the spectrum.
I have read comments that compression is the most misunderstood audio process but i really think it is equalization. it might be the most over and under used audio processing tool at the same time. what complicates the matter with eq is factors intrinsic to our humanity. we perceive different frequency different ways. some frequencies will sound louder or quieter than there actual volume. this is why some audio hardware has a “loudness” button. Also humans usually try and fix thing by addition. This translates to equalization in a tendency to boost a frequency first. Often it is easier and achieves better result to cut a frequency. You can accentuate one frequency by reducing another frequency sometimes. And will tend not to muddy up the sound. then of course there is the factor of listening fatigue. This affects both the listener and the producer of music. Some ranges become irritating to the listener quickly and as the producer your judgment is eroded the longer you listen.
Then there is the matter of equipment and the psychics of sound. When mixing and mastering studio monitors are preferable. The idea of monitor is to have a flat response curve across the whole spectrum and to be as transparent as possible. But there is no replacement for listening on different and greatly varying equipment especially for the getting the tricky low end right. Playing an instrument needs the same consideration to dial in the right sound also. Your practice amp, gigging amp, and the house pa is going to affect the sound differently and you have to consider how your sound is going to fit with the rest of the band. The low end is complicated by the psychics of sound as well as some other spots it the spectrum. Low sounds are harder to hear at low volumes. This is why a spectrum analyzer can be a useful tool to see what makes up a sound but you can not paint by decibels because our ears perceive sound differently than the psychical reality of sound.
Below is a list of guidelines of what frequency does what. and they are just that… guidelines. I used several sources and personal experience and experimentation to compile them. there are no hard and fast rules when it comes to eq. Sometimes I think professorial sound engineers do a disservice to amateurs and hobbyists by declaring what should be boosted and cut. it really depends on the source material and the entire mix. Also pros benefit from the skilled arrangements, professional musicians and vocalists, quality gear through out the entire signal chain, good microphone technique that mere mortals like myself do not always have. A lot of the eq advice is intend to get a “professional sound” which general means sounding like everything else on the radio that is fine but I would strongly suggest that you try and achieve the sound you want. a better understanding of the equalization will help you achieve that sound whether recording, mixing, mastering, finding that killer guitar sound or designing filters and tone sections of audio devices. Also remember equalization is not a magic bullet. If the sound is bad to start with is really does work with other sounds eq is not going to fix it. Eq is a polisher and shaper and can shoe horn tracks into a mix but it will not change water into wine.
The Low Down
20hz is the very low end of human hearing. 20-40hz is out of instrument range. This is the rumble of an earthquake, thunder of anything else earth shaking. Usually nothing desirable can come from a boost in this range. It sometimes can cause problems. Ambient sound like that of train or freeway or things moving in the room can rumble its way into ruining your mix. It is often completely filtered out. A lot of sound systems don’t even go this low.
Here Comes the Bass
40hz to 80hz or the 1st octave is the sub-bass of the “feel” of the bass. Its an important range for hip-hop, dance or electronic music. If you want to rattle an impala at a stop light or send thunderous pulse through the planks of a dance floor this range is for you. Bass is also hard to work with. These frequencies are made for sub woofers or large speakers. Small sound systems and even monitors frequency response rolls off in this region. This is compounded by psychics. Low end frequencies are not heard as well by human ears at low volumes. You often hear that you should try and listen on different and varying sound systems which is absolutely true but you should also listen at different volumes. while true of all sounds varied listening is critical in this range. Despite monitor’s transparency they can under emphasize bass especially small monitors. Due to the physics small speakers have trouble replicating low frequencies. This is the reason for bass boost on small systems and headphone products. The danger here is boosting the bass to overcompensate for poor bass response or listening at low volume levels only to find it overwhelms the mix at high volumes or on systems large speakers and sub woofers that produce more bass. It usually is enough to boost just the baseline or bass drum or both to get some nice tight powerful bass. Boosting to many tracks in this area can easily over power the everything else. Often all other instrument these in this range are completely filtered out.
Boom, Boom, Boom
100hz has the boom. Often guitars or other instruments will sound boomy and a cut at 100hz will remove that quality. at 100hz bass and guitar tend to blur together cutting the guitar here helps separate the two. A boost at 100hz can also add fullness to a thin sound.
200hz-250hz can add fullness to vocals but also muddy things up quickly. It is a good place to start look for mud in vocals. Small reduction or boosts can be help but changes in this range can become dramatic quickly. Mud and fullness of other acoustic instruments hang out around here also. Slight boosts to fill out a thin sounding acoustic guitar is common in this range. Also this is the range the fullness of a snare and gong sound of cymbals usually reside. 250hz-600hz is the borderlands between midrange and bass. Some fullness for vocals can be found hear also. if your kick drum or other low register percussion has that icky cardboard box sound a cut some around 300hz to 400hz can get rid of it. this same range is also a good place to get space between the baseline and bass drum.
Middle of the Road
600hz-4khz is the midrange. This is tricky area. Subtly is the key for it is easy to get unintended result. In this range it is easy to induce listen fatigue. It is also the range in which sounds edge and aggressiveness come form but it is an extremely fine line even if you are making aggressive music. You can think of it as the telephone band. If you create a step bell curve over these frequencies cut almost all the frequencies on either side and greatly boost most the ones inside of the bell and you get the telephone sound. The sound refered to by a host of hegatice terms like cheap, plastic, tinny, toy sounding, unmusical, that is almost universally loathed is prevalent around 800hz. 800hz is the area where that can boost or reduce the punchiness of a base guitar but is most often reduced to remove that cheap sound in other instruments.
Climbing above 800hz between 2khz-4khz is the area that the attack of the beater hitting a percussion instrument and the attack of some other instruments can be accentuated or diminished. This is approaching the presence range so can determine how much the sound stands out in the mix. Sound can really mush together in this range so it can take so work to get everything to fit.
Stage Presence
4khz-6khz is usually the frequency people are talking about when the word presence is used. The presence knob on a guitar amp boosts these frequencies. These frequencies affect how close the sound seems and can help separates it form the rest of the mix. It is the range that can make vocals or instrument solos seem “up front.” It is also easy to abuse. To much boost can easily become grating and listening fatigue will almost assuredly be induced.
Sssssssssssssh!
7khz is the sibilance or “s” sound area of the frequency spectrum. This where you can reduce the unpleasant and sometimes overpowering “s” sounds known as de-essing. It can work wonders but if over applied can take the life out of the vocal track.
Way Up High
7k-8k is where the brightness of cymbals and other high register percussion is. It is often referred to shimmer or sizzle. It can all add some bite to other instruments. Sometimes boosting in this area can yield a metallic sound.
8k and above is often referred to as air, brilliance, breath sound, or sparkle. These “air” frequencies are where that unpleasant sound often referred to as the ice pick sound or brittleness can be dealt or a sound brightened up and sparkle added. 10k is a good starting point to look at adding some brilliance. 15k and above is more the area referred as “air.”
Some General Tips:
Types of eq vary greatly(it would take an article just as long to explain them all.) the best eq hardware or software is one that you like the sound of and you have a good understanding of and find easy to use.
A lot of the time use eq is addition by subtraction.
A spectrum analyzer is a good tool can be useful and is a great learning tool to see what makes up what sounds.
It helps to thing of the frequency spectrum in 3 dimensional terms.
Remember there is a ying-yang quality to there frequency spectrum. A boost will diminish something else etc.
Don’t for get panning. Eq and panning go hand and hand to help everything sit in the mix
Listen to your sounds on as many different systems as possible at different volumes.
Do not rely on numbers use your ears. Experiment nothing is set in stone.
Mix in shorter focused sessions and don’t burn your ears out.
Have fun.
