How To… Record Acoustics
Capturing the essence of the humble acoustic guitar can be a tricky task, but our bluffer’s guide will make a record producer out of you in no time…
Life would be a lot simpler if there was one perfect method of recording acoustic guitar that everybody agreed with. However, if you ask 10 engineers to name their favourite technique you’ll likely get 10 completely different answers. Some engineers only ever use a single microphone to capture the sound, while others prefer to blend the sound of two or more mics.
The best engineers understand the benefits and pitfalls of a number of techniques and adapt their mic’ing approach to suit the job in hand. In this tutorial, we’ll look at how to get set up along with tips on how to produce great results from using one microphone to capture the whole sound.
Tools for the job
Acoustic guitars come in a wide range of flavours, ranging from the warm, mellow tones of nylon-strung classical and Spanish guitars to the bright, metallic sound of resonator types, such as Dobros; the full-bodied folksy vibe of a dreadnought to the distinctive sprightly tone of a gypsy jazz guitar. And then, of course, there are 12-strings … Thankfully, no matter what style of acoustic guitar is used, the methods employed to record it remain the same.
Of course, you won’t be able to make a classical guitar sound like a resonator with recording techniques, so it’s very important to make sure that you choose the right instrument for the job in the first place.
Prior to the session, it’s worth checking that the guitar is in the best possible condition. The age of the strings will affect the tone, and be aware that the gauge used will make quite a big contribution to the sound: light-gauge strings will produce a thinner tone than heavy ones. Also, the type of plectrum (if used) will influence the final result: a thinner one providing more percussive energy from the strumming, and a thicker one generating more volume thanks to its heavier attack.
Once the guitar is in optimum condition, listen to how it sounds in the room, as it’s the way the instrument interacts with the recording environment that has one of the most profound effects on the sound. Unlike vocals, that are best captured with as little room ambience as possible, acoustic guitars positively benefit from the natural reverb of a good recording room. Generally, a reasonably lively room with wooden floors will give the best results. Also, try different rooms, as you may find that the guitar actually sounds best in the kitchen!
Setting up and selecting mics
Tone on the range
With the guitar sounding great in the recording environment, it’s time to think about the best way of capturing the sound. Most engineers choose condenser microphones to record acoustic guitars, as they are often more flattering than dynamic types. Opinions differ as to whether a large or small diaphragm condenser is preferred; however, the sound of the instrument and the role it will play in the final mix should influence the choice to a greater degree. Even with the best EQ and compression, a midrange-y parlour guitar will just not cut it if your track requires a bass-y jumbo-style sound.
Large diaphragms tend to have a fatter, full-bodied sound, which is often desirable if the guitar is a featured instrument, as you would hear in, say, a solo singer/songwriter performance. Small diaphragm mics are usually favoured for their exceptionally detailed top-end response, which is useful to help the guitar cut through a busy mix.
That’s not to say that dynamic mics are completely unsuitable, though, as a well-positioned dynamic mic will sound better than an expensive but poorly placed condenser. Ribbon mics (which are a type of dynamic microphone) can sound gorgeous on an acoustic guitar, as they often sound big and warm but still capture the delicacy and detail of the sound. Also, the bi-directional response of ribbons picks up a decent amount of natural room ambience. Now, not all of us have the luxury of choosing any mic that takes our fancy, but as indicated above, an inexpensive and carefully positioned mic should produce satisfying results.
Positioning your microphone
The most common mistake made by novice engineers is to point the mic straight at the soundhole. Sure, it looks like the right thing to do, but this position often exaggerates any low-end boom, that could clutter up your mix.
It’s far better to find a position that picks up a more even balance of the instrument’s sound. Remember, an acoustic guitar’s sound is made up of several elements: resonances from the soundhole, wooden panels and internal bracing, as well as the sound of the strings, so finding a spot that captures a larger slice of the complete sound is best.
Aim to find a position that offers a decent overview of the guitar’s sound without too much unwanted low-end information, especially when using a directional mic with a fixed cardioid polar pattern. If you have a mic with an omnidirectional pick-up pattern you can afford to move in a little closer if desired, as the low-end boost caused by the proximity effect of directional mics isn’t an issue.
Also, an omni mic will capture a nice, even amount of room sound. One problem with this mic position is that with some instruments the sound can lack body, which can be an issue if the guitar is a main part of the recording.
If, however, the guitar forms part of a busy mix, the thinner sound can be positively advantageous, particularly if you want the rhythmic strumming of the strings to cut through without too much midrange frequency information cluttering up the production. Another problem can arise from unwanted noises, either from the player’s fingers sliding along the strings, or annoying fret buzzes. A good solution to this problem is to position the mic away from the neck and further along the body towards the bridge.
For a more full-bodied tone, experiment with positions that have the microphone placed above the sound-hole, angled downwards – this position is excellent for capturing a well-rounded sound while avoiding the blast of air emanating from the sound-hole.
If the guitar you’re recording is an electro-acoustic then you can DI it onto a separate channel (preferably through a preamp first to add warmth) and then blend it in later (if required) to thicken the sound. (Granted, we’re meant to be talking about recording with just one mic, but as this is a pickup we can get away with it!).
Now, it’s time to delve deeper and discover how multi-mic’ing can offer a wider variety of tonal options. Don’t be fooled, though, it’s no good throwing up several randomly placed mics and hoping for the best, you still need to think about and – crucially – listen to the sound of the instrument before deciding where the best sounds will be captured. Points mentioned in Part 1, such as the quality of the recording environment, condition of the instrument and an understanding of whereabouts on the guitar various tones can be captured are still relevant and should be used as a good starting point before extra mics are brought into play. As we shall see, using more than one mic – or a combination of a microphone and a DI can present its own problems as well as offering you more flexibility.
There are two main reasons why we might want to use two or more mics to record acoustic guitar. Firstly, microphones can be placed at wildly different-sounding parts of the guitar to achieve a coherent blend. With just one mic, the chosen position must capture a fairly broad range of the tones that the instrument is capable of. However, using two mics, for example, one could be positioned near the bridge where the sound is full-bodied but might lack top-end detail, and a second mic could be placed facing the neck, capturing a bright, detailed sound that would probably be too thin to be used alone.
Secondly, two or more mics offer the possibility of stereo recording.When using multi-mic techniques to create a mono signal (which can later be panned anywhere in the stereo picture), there are several ways of going about it to achieve the desired effect.
As previously mentioned, mics can be used to pick up contrasting tones that would be practically useless used on their own, but sound great when mixed together. However, another method is to try to get the best overall sound from the first mic – as you would when using single mic techniques – then embellish the sound with a second mic that emphasises certain aspects of the guitar’s tone that the first mic is lacking. For example, if your first mic is in the sweet spot (the classic 12th-fret position is often a good starting point) but lacks body, a second mic could be placed where more bottom-heavy tones are heard – near the bridge of the guitar, behind the instrument or even close to the soundhole.
Similarly, if the first microphone is missing some high-frequency information, a second mic positioned somewhere further up the fretboard towards the headstock might produce a more natural tone than adding some top-end EQ to the main microphone.
Another reason for using more than one mic is to capture some of the recording room’s natural reverb. Again, the main mic should capture a good overall guitar sound while another mic, placed at a distance, will add ambience and life. Of course, the techniques already mentioned can be used simultaneously, so that you have a couple of close mics capturing the broad tone of the instrument while a third mic picks up the room sound; two spaced room mics can produce a very good stereo effect. As always when using multi-mic set-ups, check the phase relationship between microphones by inverting the polarity of one channel; if the sound becomes fuller and more focused, use that configuration.
Recording acoustic guitar in stereo can give excellent results, particularly when it’s a featured instrument in a predominantly acoustic track. There are several techniques that can be employed for this, but a detailed study of stereo recording is beyond the scope of this article. That said, the mid/side method – explained in the step by step guide – is worth trying as it can produce a very natural and convincing stereo image.
Mid/side stereo acoustic guitar
Often, when musicians request ‘stereo’ acoustic guitar, they actually mean two separate mono guitars playing the same part, panned left and right. This double-tracking method can sound really good in many rock/pop recordings, helping to create a sense of width and space. Some engineers like to create two almost identical recordings, using the same mic in the same position on the same guitar. However, it’s worth experimenting with different mics and positions – even different guitars – to determine what works best for the song.
Some acoustic guitars have pickups fitted, enabling the instrument to be DI’d or plugged into an amplifier (effectively turning it into a semi-acoustic guitar). Most engineers prefer to use microphones rather that a DI when recording acoustic instruments, but sometimes a blend of microphone and DI signals can produce good results. Just remember that the DI signal will hit your recorder slightly before the mic signal, which can cause issues with phase.
So far, we have assumed that the acoustic guitar is being recorded in isolation – it can be tricky getting a really good sound if it’s being played in a small space, along with loud drums and amplified sounds. That said, many singer/songwriters like to lay down their guitar and vocal tracks simultaneously. A good trick here is to use a bi-directional (figure 8) polar pattern with both the vocal and guitar mic. Bi-directional microphones are extremely effective at rejecting sound that arrives from the sides, so if each mic is positioned so that the null side points towards the unwanted sound, good separation can be achieved.
Well-recorded acoustic guitars generally don’t require too much in the way of processing, if a natural sound is desired. However, when it forms part of a busy mix, a certain amount of low-end attenuation can help the guitar sit in the track, creating space for bass instruments. At the recording stage, a high-pass-filter on either the microphone or preamp can be engaged, helping to eliminate boom; when mixing, a low-end shelving EQ is the best option.
Many acoustic guitar tracks benefit from a touch of top-end boost to generate a bit of sparkle. Anything from 10kHz upwards will add some zing to the sound, but a healthy boost around 16kHz can add a lovely sense of air and space.
Talking of space, a touch of reverb often sounds nice on acoustic guitars, particularly if they’ve been recorded with very little room ambience present; the length of the reverb will be determined by the nature and tempo of the song. A little bit of compression can help franticly-strummed rhythm guitars sit in the mix if the compressor is well set-up to respond to the tempo of the track.
Excessive pick sounds can be tamed by using a very fast attack time to dull the presence of the plectrum. Acoustic guitars feature in all sorts of recordings in any number of styles, ranging from solo singer/songwriter performances where it is the main accompaniment, to complex mixes where it provides a rhythmic bedrock. Experimenting with the techniques explained here should allow you to make professional-sounding acoustic guitar recordings with confidence.