Figure-of-eight mics have a ‘deaf’ null at 90 degrees off-axis on both sides.
Arranged carefully, they can offer a worthwhile amount of separation even on sources that are quite close together, such as someone singing and playing guitar simultaneously.
T I P : The commercially available
curved sound absorbers designed to be used behind vocal mics are also very effective if placed behind omni or figure-of-eight mics when recording acoustic instruments, as they cut down on the unwanted room reflections reaching the rear of the mic. Rather like an omni, most figure-of-eight mics don’t suf-fer tonal colouration as you move off-axis, though the overall level falls away to zero once you get to 90 degrees off-axis. However, you
(or guitar), you don’t need to achieve perfect separation – just enough to allow you to balance and, if necessary, EQ the two sounds adequately.
Finding the Optimum Mic Position
When trying to record an acoustic guitar, the first challenge is to locate the best position for the mic. Usually the optimum microphone distance is between 10 and 18 inches (25–45cm) from the guitar body where the mic will ‘hear’ a large part of the guitar’s vibrating surfaces, and there will be little proximity effect if using a directional mic. A mistake commonly made by inexperienced musicians is to place the mic directly in front of the guitar’s sound-hole. It may seem like this is where most of the sound comes from, but unless the guitar has a very small body this position invariably produces an unpleasantly muddy
and boomy tone with poor definition. A much better starting point is to direct the microphone towards the point where the guitar’s neck joins the body, as this usually produces a much better-balanced sound. However, every guitar is different and while this mic position will probably provide a very acceptable sound, don’t automatically assume this will give you the best or most representative sound for the specific guitar. One of the things we often do during Studio SOS visits is to ask the client to play the guitar while monitoring the sound via headphones.
As they play we move the mic around so that they can hear the effect of changing the mic position, and in most cases they’re absolutely astounded at how dramatic a difference this makes.
Where somebody else is playing the guitar, we have found that the best method for finding the optimum mic position is simply to monitor the microphone’s output using good quality headphones, and while the musician plays you can then move the mic around by hand until you find a position that delivers the best sound. With the ideal positioning identified you can then fix the mic on a stand. What you’re listening for is a tone that’s both warm and lively, but without being harsh or boomy and without any unnatural phasiness. Two common mic position alternatives to the neck/body joint, that often work well, are firstly below the guitar body looking back up towards the bridge – which tends to give a more rounded lower end weight with many guitars (and less fret noise) – or to place the mic alongside the player’s right or left ear looking down over their shoulder. If you want a thinner tone, perhaps to help the guitar cut through without muddying the mix, then moving the mic more towards the headstock end often helps.
Provided that you take care with the microphone placement at the recording stage, you should be able to capture a natural sound that works well in the mix without requiring much further processing. However, unless the recording is of just a solo guitar, some equalisation often helps to make it blend with other components in the mix. Where a strummed acoustic guitar is part of a busy arrangement alongside bass and drums, filtering the low end quite severely – reducing everything below maybe 300Hz using an 18dB/octave low-cut filter – is standard practice, as this produces a guitar sound with very little body but plenty of percussive definition. Don’t worry about how the guitar sounds in isolation when soloed – it will obviously sound
quite thin – it’s how it works in the context of the complete mix that’s important. If used as a rhythmic bed, the equalised acoustic guitar should almost blend with the hi-hat sound.
If you feel the guitar needs more clarity and presence, a shelving-EQ boost in the 7 to 10kHz region will add sparkle and polish to the result without reaching far enough down the spectrum to give the sound an aggressive edge, but once again you must evaluate the results by listening to the complete mix rather than just the guitar in isolation. Problems we’ve encountered often involve the user boosting at too low a frequency, typically in the 2 to 4kHz range which, although it helps the guitar cut through in a mix, can also make it sound unpleasantly harsh. Boominess or boxiness can be tackled using a suitably tuned parametric equaliser in ‘cut’ mode, if a simple, shelving low-cut doesn’t do the trick – but it’s always better to avoid this problem in the first place by taking the time to find the best mic position that avoids capturing a boomy sound. If you need to cut out boominess using EQ, start by
Finding the ‘sweet spot’ is much easier if you are monitoring the output as you move the mic around.
Narrow-band EQ cut can help tackle a single boomy or boxy-sounding frequency without altering the overall tonality.
T I P : Ultimately every sound has
to be judged in the context of the whole mix. It is best not to spend too much time trying to equalise individual instruments to sound as close as possible to the ‘finished’
sound you think they will need in the mix, whilst recording them. You may well have to change your approach once the rest of the track is play-ing and if you have used too much EQ or compression, you may have already compromised your options.
sweeping through the 100Hz to 300Hz range with a moderately narrow-bandwidth EQ boost, in order to locate the trouble spot. When you’ve found the unpleasant boomy frequency adjust the gain control to apply as much cut at that frequency as is necessary, while also tweaking the bandwidth or Q control to affect only the troublesome frequency range.