Recording a solo fingerstyle-guitar performance, a singer/songwriter with acoustic accompaniment, or an acoustic rhythm track in a band is very different from recording an electric guitar (a topic we tackled in the December ’15 issue), employing different microphones, placement, and technique. If you’ve had an inkling to try your hand at recording acoustic guitars, here are a few essential steps.
There’s something of an inverse relationship between how an acoustic-guitar track will “sit” in the mix and how to capture that track; in brief, the bigger the arrangement (including electric guitars, bass, drums, maybe keys, and vocals), the simpler and narrower your approach might be in order to keep the acoustic part tight and focused within a dense soundscape. On the flipside, if the track will be part of a simple arrangement where it needs to sound bigger, the technique will often be more complex. If your home-studio mic selection is limited, you might have no choice but to approach everything the same way. Ideally, though, you will adapt your technique to the goal at hand.
The Recording Space
Because acoustic guitars are recorded in “the air” of an acoustic space, your effort will benefit greatly from a good-sounding room. It’s best to avoid a room (or portion thereof) where you hear unduly emphasized resonances or reflections. Any space that fights back sonically should be treated with some sort of damping.
The relative softness of an acoustic guitar’s output and the higher mic preamp levels required to capture it means quiet space is essential if you don’t want excessive “character” captured along with it. Those factors also make it critical that you listen closely to tracks at idle, with preamps turned up to necessary levels and everything running through your interface into the digital audio workstation (DAW). If you hear a lot of static, hum, white noise, work your way down the signal chain to find and eliminate noisy links.
If a low-budget copy of a ball-end dynamic mic is the only tool in your box, don’t let it stop you. Traditionally, condenser mics have been the primary choice for recording acoustic guitars – they have the fidelity and sensitivity to capture the nuances, along with the crucial high-end detail and low-end solidity, plus they provide the output level without inducing the noise inherent in a cranked preamp. Condenser mics can be placed at some distance from the guitar, which enables the sound to “breathe,” meaning they capture a larger soundscape from the instrument rather than a focused slice.
The ability to put distance between the mic and the guitar means tracks are less susceptible to peaks or dropouts when a performer is unable to sit entirely still. On one hand, guitarists accustomed to moving and grooving with the music do need to learn to sit relatively still while tracking acoustic parts. On the other, you don’t want to cramp a player’s style or get them sitting so stiffly it’s reflected in a performance.
Putting just a little distance between mic(s) and guitar provides a cushion, of sorts, that absorbs fluctuations in signal level when the player moves a little, helping minimize peaks or troughs in the track.
While the high-end detail afforded by small-diaphragm condensers has made them the mic of choice on acoustic guitars, the unforgiving clarity of digital recording has found more and more recordists enjoying large-diaphragm condensers for this application, and plenty have been turning to ribbon mics, too. A good ribbon mic, with a little high-end boost if necessary, can capture a deep, rich, warm acoustic tone that cures the coldness or brittleness heard in some condenser mics (cheaper ones in particular). To make a ribbon work on acoustic, however, you need a clean, high-gain preamp, or you’re likely to be weighed down with noise; for that reason, they also tend to be easier to use on punchy rhythm-guitar parts performed on acoustic, where you’re hammering out a steady, aggressive chord progression.
As with miking amps, the best way to find the right place to put your acoustic guitar mic is to listen to the sound your guitar produces from a number of places (while someone else plays it), record it with a mic placed there, and listen back. First, though, do not place the microphone pointing straight into the sound hole; this can take some getting used to, because whenever you take a guitar with no pickup to an acoustic gig, the sound engineer points an SM57 right at the sound hole. This does not produce the most flattering acoustic tone, but does tend to capture the most volume in a live situation. It’s a livable compromise.
An acoustic guitar’s sound isn’t produced from the sound hole alone. Rather, it’s the point where sound is reflected from the backside of the top and off of the back of the guitar, plus it allows the resonant surfaces of the body to flex. Much of the tone is produced around the bridge and the broad portions of the bass bout, while other frequencies are produced in the upper bout, where the fretboard joins the body. Sound coming off the back of the guitar has its own tone. The best technique captures a blend of these sounds to accurately represent the full picture.
One of the most popular traditional studio techniques for recording mono acoustic guitar involves placing a mic near the 12th fret a few inches from and aimed toward the end of the fingerboard (at the body end), but not into the sound hole. This captures a bright, lively tone with body and some string sound for jangle. To mellow it, move the mic slightly lower and more toward the meat of the upper bout, firing more directly at the guitar’s top; test the tone by aiming at both the bass and treble side of the upper bout – they will be quite different.
Another position that captures a full, woody, and somewhat less jangly tone is found by pointing a mic at the guitar’s top near the lower bout just below and behind the bridge. Moving it further down and away from the lower end of the guitar and aiming it at the edge of the body (where the top meets the side) can produce another interesting tone – a little more edgy and cutting, with a snappy upper-mids presence.
A rich, full, yet crisp tone can be had by positioning a mic about head-high with the performer, 6″ down the shoulder from their right ear and 10″ out from their face, firing down toward the bass side of the lower bout of the instrument. Another quirky but occasionally successful placement is found by positioning a mic similarly, but firing from behind the player, aimed over their right shoulder. This achieves a modicum of the sound the player hears, which isn’t necessarily the best tonal picture of the instrument, but can be useful.
As with recording guitar amps, you can often achieve a broader, more multi-dimensional sound from an acoustic by carefully positioning more than one microphone. Multi-mic techniques are useful when you want to paint a big picture with the acoustic guitar in a solo recording or in an arrangement with few other instruments when you want a broad, spacious voice from one. When you want to coax the richest, deepest, most “in-the-room” acoustic guitar sounds onto a recording, you’ll often turn to two or more mics.
Classic Stereo Techniques
Obvious candidates for multi-mic acoustic-guitar recording are found in any classic stereo-mic techniques commonly used to capture acoustic instruments. Note that most of these techniques are best achieved with a pair of mics of the same make and model. If you just don’t have two of the same mic and still want to record in stereo, try any of these with your two most closely matched mics. If it works, it works, and the listener is unlikely to hit the stop button and shout, “Hey, those stereo mics aren’t matched!”
Spaced Pair or AB Pair
Perhaps the simplest and most obvious stereo-mic setup is the spaced pair. Just as its name implies (it’s also called “AB pair”), this configuration involves using identical microphones – usually condensers – spaced some distance from each other but on the same horizontal and vertical planes (height- and distance-wise from source). These mics are usually placed away from the sound source, too, rather than close, to enable the sound to bloom into the full stereo image.
When setting a spaced stereo pair, engineers traditionally try to observe the “three to one rule,” which says they should be placed three times as far from each other as they are from the sound source, while each should be the exact same distance from the sound source. This configuration can work for wide/semi-wide stereo panning, but even when the rule is observed, you can get sonic oddities from phase cancellation if you find you need to pan them to the center in mono. Also, when used super-wide, it can sometimes give the impression there’s a “hole” in the middle of the soundscape, a perception that other stereo techniques seek to cure, but this is minimized with the use of omni mics, or some recordists place a third mic equidistant between the two to capture the center “mono” image.
Coincident or XY Pair
Another traditional configuration often used on acoustic guitars, the coincident (also known as XY) pair seeks to repair the “hole” in the middle while capturing a full, broad stereo image. Slightly different versions of this setup exist, with variations in each. One common method (Variation A) says you mount two microphones at a 90-degree angle to each other, with their capsules one above the other, nearly touching. The other popular technique (Variation B) has the mics on the same plane, with the capsules positioned as if firing across each other. With either, you can vary the angle of the mics, tightening it to 60 or 70 degrees for a narrow stereo field, or opening it up to 120 degrees for a broader soundscape. Note that when setting up this pair, one must track the mic that is aimed to the right of the sound source as the “right mic,” and the mic aimed left as the “left mic,” rather than confusing the fact that the bulk of the body of the right mic (if it’s an end-fire mic, or a side-fire mic positioned horizontally) will lie to your left hand as you face the sound source.
Condenser mics are the traditional choice for the XY pair, though proper ribbon mics also work. The resultant two-channel recording can be panned somewhat as desired to vary the width of the stereo image after the fact, but a panning that mirrors the angle at which the mics were originally placed one to the other will most accurately re-create the performance. This setup also works well when both mics are panned to mono, which will exhibit minimal phase issues.
Another method used to capture a broad, deep, and sharp stereo field is the “near-coincident pair.” As with the coincident pair, this configuration uses two mics fairly close together, but in this case their capsules are spread some distance apart (usually six to eight inches) and angled 110 degrees away from each other at the left and right sides of the sound source. Depending on the mics, width of the sound source, and angle at which they are positioned, this technique can produce a realistic and atmospherically diffuse stereo image – and/or an indistinct center image. Put another way, compared to its sibling XY coincident pair, the near-coincident might give broad and accurate stereo, but a softer center image. Mics similar to the coincident pair work well for this, and yield slightly different results.
Baffled Omni (Dummy Head) Pair
This configuration and its variations result from the effort to record a stereo image that replicates the perception of human hearing, and involves positioning an omni mic on each side of a Jeklin disc or spherical baffle that creates the sonic “shadow” of the human head (or an actual mannequin head with mics positioned where the ears would be). Omni mics are a critical part of this configuration, since the human ear is essentially an omni listening device but for the head that gets in the way. You can get interesting results with good cardioid and figure-8 mics, too.
This technique can produce a realistic stereo image, but does have a few drawbacks. Again, it can suffer from a slight hole in the middle, and the accuracy of its stereo reproduction can be extremely dependent upon the listener’s position. Which is to say, they’ll be capturing a stereo image with the actual ears on either side of their own head, so translating them via a reproduction of such in recording can be taking it all a step too far, where another stereo technique might provide a broad, realistic, stereo field that is less dependent on the listener’s position.
When recording acoustic guitar, you can also achieve this technique without the dummy head or Jeklin disc by expanding the “over the shoulder” single-mic technique from above. Set your mic stands behind the guitarist and position each of two mics a few inches out from the ears, and firing slightly downward toward an imaginary point about 10″ in front of the guitar if you are using cardioids or figure-8s rather than omnis. To increase the low-end body in your acoustic tracks, use this technique with the performer facing a corner of the room, which takes advantage of the corner-loading effect; the mics firing over the guitarist’s shoulders will also pick up the bass-heavy reflected sound from the corner, and add significant weight to the tracks.
Dual-Mono Acoustic Guitar
Strictly speaking, a true stereo image should capture identical left and right images of a sound source, as the above techniques do. If you use two different mics and/or place two mics in very different and unequal positions around the sound source, you aren’t really recording in stereo, but in “dual mono.” Which is not to rule out such a technique at all – great results can be obtained from this kind of placement, and two different mics, differently placed, can be more useful in the final mix than precisely positioned stereo setups of matched mic pairs. Consider that an acoustic guitar produces very different tones from different parts of its body and neck, and it’s clear interesting results come from placing different mics at different points around the guitar and either blending them together in mono or positioning them left-to-right to some degree across the field.
Look at the single-mic positions mentioned earlier and consider that you can use a combination of any two. Even when used in “pseudo stereo” – two differently-recorded points of the guitar panned in stereo – can yield a big, sonically pleasing sound. There are phase-cancellation issues with such techniques, but they can be minimized. Very usable placements include A) a mic aimed just slightly behind and below the bridge and another aimed at the edge where the guitar’s the top and side meet, at about 11 o’clock on the front of the lower bout; and, B) one mic aimed at the body edge on the treble side of the lower bout and one aimed at the meat of the top in the region of the bass side of the upper bout.
Another non-stereo two-mic technique uses one mic aimed at the front of the guitar and another firing at the portion of the back of the guitar where sound emerging from the player’s side, under their strumming arm. A big part of any acoustic guitar’s overall tone emanates from its back, and blending this mic with a traditional front placement can produce depth and dimension. Note, though, that because the two mics are firing in opposite directions, you’ll usually need to reverse the phase on the back mic, unless you are using mics which are already reverse-phase of each other.
To get even more lively back-of-guitar tone into the mic, have the guitarist hold the instrument slightly away from his or her body while playing (if it doesn’t impede their performance) to avoid damping the resonance of that part of the instrument.
In addition to being Vintage Guitar’s resident amp historian, Dave Hunter is the author of several books on gear and technique, including The Home Recording Handbook (Backbeat Books, 2012), which covers in further detail many of the techniques discussed in this series.
This article originally appeared in VG August 2016 issue. All copyrights are by the author and Vintage Guitar magazine. Unauthorized replication or use is strictly prohibited.
The Art of Home Recording — In this series, VG will equip readers with the knowledge and skill to achieve professional-sounding home recordings.
Part 1: Building a Studio
Part 2: Microphones and Their Uses
Part 3: Recording Electric Guitars
Part 4: Recording Acoustic Guitars