An earlier article discussed a number of approaches to miking acoustic guitars in a recording environment; those approaches used a single microphone, which works great in many applications. But there’s no need to limit yourself to a single microphone when the tones and textures available with multiple microphones can add a new dimension to your recordings, so here are some tried and true microphone setups that may prove to provide the perfect sound for a given song.

Mono Compatibility
Before discussing ways to record the acoustic with two microphones, a word about phase. When you play a note, sound waves travel from the sound source (your guitar) to the microphone; this takes a certain amount of time, determined by the distance between the two. With two mics, you must pay attention to the distance between the sound source and each of the microphone capsules; if the signal travels a greater difference to one microphone than to the other, phase issues can arise that will impact the mono compatibility of the track. While this might not seem to be an issue — after all, everybody listens in stereo — in the real world, the results of phase issues range from unwelcome tonal changes to the instrument effectively disappearing from the mix. In general, the result of phase problems are that come frequencies will be louder while others get cancelled out. It’s worthwhile to check stereo signals by panning both tracks to the center to be sure that the sound is still usable.

Coincident XY 2
A simple approach to stereo miking is the coincident X-Y method. With X-Y, two cardioid microphones of the same model are set up with capsules placed as close as possible and facing each other at a 90-degree angle. An easy way to do this is to place a pair of mics on a stereo mic holder with the capsules stacked one above the other. Position the mics facing directly at the sound source and panned left and right in your mixer or DAW; a little experimentation shows the distance from the guitar will have a pretty large impact on the recorded sound of the instrument. Because of the negligible distance between the two capsules, sound arrives at both mics at nearly the same time, eliminating (or at least greatly reducing) possible phase problems.

Near Coincident

A variation of coincident X-Y miking is a near-coincident setup; in this case, rather than placing the capsules as close as possible to each other, use cardioid mics set at the same 90-degree angle, but separate the mics — as close as about four inches, but up to 12 inches apart; this setup gives a wider image, and though phase problems can occur, they are minimized, at least compared with some of the other setups we’ll discuss later.

ORTF Stereo
ORTF, named for the French broadcasting network that came up with it, is a stereo setup intended to emulate the spacing of human ears, with the angle of the microphones intended to emulate the shadow effect of the human head. The ORTF setup places two cardioid microphones spaced 17 centimeters apart, with an angle of 110 degrees between the two capsules. Setting mics up in an ORTF setup provides a wider stereo image than coincident miking, yet retains a bit more mono information than a spaced-pair setup.

Spaced Pair
A spaced-pair setup uses two cardioid (or omni) microphones, placed from one foot to four feet apart, and pointed at the guitar from a distance of one foot to four feet. The main concern is to make sure that the two microphone capsules are on a plane so that the distance between each microphone and the guitar is the same. Spaced pair setups are the most susceptible to phase issues, so be sure and check; even the guitarist shifting in the chair can make a difference, so this does require a bit more supervision to work well. But when it does work well, it’s a great sound.

Space Hi and Low Side
A variant of the spaced-pair setup has become fairly common; in this case, place one microphone 4-6 inches from the guitar, between the soundhole and the neck side of the guitar, a couple of inches below the neck (the same placement as recording an acoustic guitar in mono). The other microphone, however, should be placed at about the level of the guitarist’s shoulder, a foot or so from the front of the instrument and facing down toward the guitar. This isn’t a “stereo” technique, but the two microphones combine quite nicely (be sure to check for mono compatibility).

One Final Tip
Sometimes a particular song needs two passes of acoustic guitars; if you’re putting guitars on a project and decide to add a second guitar, you have two good options. The first would be to create two new tracks and record a second stereo pair. If you do, consider reversing the panning of the second track — right-left rather than left-right.

The other approach is to make a practice of recording the stereo guitars onto two mono tracks rather than to one stereo track. When you want to add a second guitar, simply take one of those two tracks out of record, so that you’re replacing one track of the original take. This method is quick, and when mixing the project, the two-guitar songs will sit in the acoustic space (with the same panning) as the single-guitar tracks. There’s another advantage, too: the first pass of acoustic will be in stereo, of course, but when you take one of the tracks out of record for the second pass, it means that the original guitar pass will be panned to one side of his headphones, while the second pass will be panned to the other side, all accomplished by clicking a single button.

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