Acoustic guitars have always been notoriously tough to record, but that doesn't mean you can't make your tracks sound warm, full and natural. We'll examine some of the tried-and-true ways to use microphones, pickups-or a combination of both-to capture well-balanced acoustic tones that can help you cut through almost any mix.
Let's begin with the obvious first step: changing your strings. While I have debated whether to bother with this chore countless times before starting an acoustic recording, I'm always glad to hear those fresh, crisp sounds from my guitar when I do. Aside of making your instrument project more tone, new strings also stay in tune better than old, dead strings. An acoustic that won't stay in tune has crushed the vibe of many a session. So do yourself a favor and start with fresh strings and a good tuner.
Playing technique will also influence the tone of the instrument. A fingerstyle performane will typically deliver a darker, warmer tone than playing with a pick. However, picks will provide more attack and note definition, especially on strummed chords. Taking it a bit further, the heavier the pick, the darker your tone will be. I like to have a combination of different picks on hand and try them out in the context of the song. Thinner picks project a brighter, lighter sound that can help cut through a dense mix, but you'll lose some lows and low midrage
The type and gauge of strings will also change the sound of your guitar. There are many different kinds of acoustic strings, ranging from the popular phosphor bronze to blends using brass, silver plated copper, and even silk and steel. No matter what type you choose, typically the heavier gauge the string, the harder they are on your fingers. But, heavier gauge strings deliver more tone, so the trade-off is often worth it when recording your guitar. I've found that D'Addario's Light Top/Medium Bottom set-with gauges that run from .012 on the high E up to .056 on the low E-works great for recording. Note that a big change in string gauge can affect the guitar's setup. You may need to have the neck adjusted if you go from, say, light to medium (or vice versa).
A two mic set-up, with the close mic at the spot where the neck meets the sound hole.
Now that your guitar has fresh strings and the tuner is ready to go, you have to decide how to best get your instrument recorded. While you could simply plug in an acoustic using a built-in pickup (provided it has one), these don't always deliver the instrument's true tone. The ambient tone of an acoustic guitar comes from the body resonating with the top and sides along with sound projecting from the soundhole. Most professional engineers start by placing a quality microphone at a well-balanced spot on the guitar-where the soundhole and neck meet. Typically, that spot will deliver a nice blend of highs, mids and lows to capture the essence of the instrument. Begin at a distance of around six inches, and move closer or farther depending if your want a more direct (closer) or ambient (farther) sound.
The type and pickup (or polar) pattern of each mic will vary, as will of course their price and quality. In general, mics with an omni pickup pattern (such as Earthworks QTC 30, DPA 4091) will record equally in all directions and tend to sound very natural and open, so they can sound great on acoustic guitars. Mics with a figure 8 polar pattern capture sound from in front of and behind the capsule, rejecting sound from the sides. Ribbon mics (such as the Royer R-121, Blue Woodpecker, and AEA R92) tend to feature the figure 8 polar pattern, and have the characteristic of being warm and pleasing to the ear.
Cardioid pattern mics are more sensitive at the front of the capsule, rejecting much of the sound both behind and on the sides. The classic Shure SM57 dynamic mic has a cardioid pattern, but is not always the best choice for acoustic due to its mid range bump and lack of low end. Condenser style mics with a large diaphragm (such as Neumann U-87, Studio Projects B1) are often a better choice for acoustic guitars, as they are inherently warm and 'big' sounding. Small diaphragm condenser mics (such as Neumann KM 184, AKG C451, Shure SM81) are also very popular for acoustic guitars, due to their crisp, clean, and focused sound.
You can capture a very balanced tone by using a large diaphragm condenser mic close to the soundhole and a second mic pointing at the bridge.
Supercardioid and hypercardioid mics pick up even more sound in front of them than cardioid. Some microphones, such as the AKG 414XLII, Audio Technica AT2050, and Røde NT2000 have selectable polar patterns, so you can dial in what best suits your recording. Also specifically for acoustics, companies such as DPA make small, high quality condenser mics with supercardioid patterns, such as their 4099G. It can be clipped directly onto your guitar, and offers a small footprint mic that can be used live as well as in the studio.
The acoustics of the room you record in will also influence the overall tone of your recording. The guitar's sound will reflect off of floors walls and ceilings. While a nice ambient room can be a good thing, a very live-sounding space can produce unwanted echoes. Play your guitar in different spots in the room and determine where the overall tone of the instrument is best. One of my tricks is to buy small pieces of bamboo flooring at a hardware store, then lay them down in front of the guitar when recording (especially in carpeted rooms). It can help project the sound of the instrument up into the mics and deliver some extra sound.
While you can get good sound from a single mic, you may also want to try using a second microphone along with the first. Blending the neck/soundhole setup with a large diaphragm condenser pointing at the body can add additional bass response. Or, you can place the second mic three or more feet away from the first mic (to avoid phase issues), which can help add depth and dimension to the sound. Record each mic on its own channel; you can then pan them near each other in the stereo field, or separate them left and right to create a sense of space. Moving the fader for each mic up or down will create a unique tonal blend.
The X/Y stereo mic technique is also popular on acoustics. Position two cardioid or super cardioid mics close together, pointing at an angle from one another of between 90 and 135 degrees. The center or their combined image should point at the guitar. I tend to place them just on top of one another, with the tips of the mics barely touching. On your mixing board, the desired width of your guitar image will depend on how far left and right you pan the two mics.
Another similar option known as the ORTFstereo technique (named for the Office deRadiodiffusion Télévision Française). Here, the tips of the two cardioid mics are up to seven inches apart, facing away from each other at a 110-degree angle.
The spaced pair technique also uses two microphones, which can be either cardioid or omni. The mics are positioned away from the guitar (as far as you desire) and are spaced at a minium of three feet apart (again, to prevent phase cancellations, which can make the combined tracks sound somewhat thin).
Using and EQ to roll off bass and add high-end sparkle.
You can also combine mics with a guitar's pickup; some instruments have multi-pickup systems, which may combine a piezo bridge pickup or body sensors with a magnetic pickup or onboard mic. If the guitar is equipped with an onboard preamp, you can use its volume, and EQ controls to shape the tone.
Generally, you'll need to use a D.I. (direct injection) box or ouboard preamp between the guitar and the mixer/audio interface. Companies such as Fishman, D-TAR, Zoom and TC Electronic also make processors specifically tailored for acoustic guitar sounds, with built-in modeling, effects, and tuners. Soundhole pickups can also be effective-especially when combined with a mic.
Any of the above pickups can be used on their own or combined with a microphone to offer a variety of tones. Microphones typically capture a more ambient and "realistic" sound, while pickup systems deliver a more of "direct" sound of the strings. However, pickup systems tend to produce an excess of midrange, with a lack of defined bass and highs. You can compensate with EQ-either on your mixer or preamp, by using an outboard device, or with a plug-in during mixdown. I've found it best with a pickup to pull down some of the low and mids, and boost up the highs. Mixed along with a good microphone, they can add a nice sense of sparkle and presence to your acoustic tone. Many engineers find that the ideal setup is a combination of a high-quality microphone (or two) along with a direct feed from a pickup. Recording each source to its own channel gives you the flexibility to create the ideal blend for each song.
No matter which method you choose, be sure to take your time and listen before you start recording-don't rely on EQ to fix it in the mix. And ohh yeah-change your strings!