SIX-STRING STRATEGIES

Dec 1, 2006 12:00 PM, By Michael Cooper

It Takes Two to Tango

For all the benefits of recording acoustic guitar in mono, there are times when two or more mics are called for. This is often the case when the guitar is the only instrument in the mix and needs to sound very big.

In such a situation, Dodd sometimes likes to use one mic placed close to the instrument and a stereo pair placed farther back to capture room ambience. (Of course, distant miking dictates that you record in a room with desirable acoustics that will enhance the recording.)

Way usually takes a different approach when miking an acoustic guitar in stereo. “Often the first thing I go for is a stereo microphone like an AKG C 24 or a Shure SM2, so that my phase problems are going to be minimal,” he says. Way suggests the Sony ECM-999PR, a discontinued stereo electret condenser, as an inexpensive alternative to the higher-priced mics. “I really like the high end” of the ECM-999PR, he explains. “It's not full bodied at all, but it's very sparkly sounding. When I'm looking for a guitar sound that, in the mix, I would be rolling off bottom on anyway, and I want it to be in stereo, I'll use that mic. It does a really nice job.” He'll sometimes add another microphone as an ambient mic to complement the Sony's sound.

Ahern has a predilection for using ribbon mics to track acoustic guitar in stereo, in part because of the coloration they add to the recording. “I don't like flat recordings,” he says without hesitation. “Sometimes I'll record Emmylou Harris's guitar with two Varacoustics [vintage RCA ribbon mics], one up by the 12th fret and the other down by the fingers of the right hand. That's a pretty interesting sound.” In this configuration, he'll typically place the ribbon mics about six inches away from the guitar. He also uses beyerdynamic M 160 and M 130 mics in a mid-side configuration, placing the mics near where the fingers are plucking the guitar (see Fig. 3 for an explanation of mid-side mic placement). The vintage, '70s-era Reslo ribbon mic is another of Ahern's favorites on acoustic guitar. (For more tips on using ribbon mics on acoustic guitar, see “Ribbon Mic Summit” in the August 2006 issue of EM, available online at www.emusician.com.)

Newland usually leans toward using an XY mic configuration for stereo-miking acoustic guitar (see Fig. 4). “If I were going to use a pair of mics, nine times out of ten I would do XY,” he affirms. “I like the punch of it. You get a little more centeredness,” he says when describing the sound of XY miking compared with that achieved by using a spaced pair of mics.

Newland is not afraid to get radical, however, when a gigantic sound is called for. On Beyond the Missouri Sky (Universal, 2003), a DVD collaboration between Pat Metheny (playing acoustic guitar) and Charlie Haden (bass), Newland notes he “went for this monstrous, huge acoustic, stereo sound. Not stereo left and right, but this wider image of the guitar. I think we had eight tracks for the acoustic on a single pass. There would be a large-diaphragm condenser, a small-diaphragm condenser pair in XY, a spaced pair, an internal mic on the guitar, and a custom DI.” Newland used all of those mic signals to varying degrees. “If there was a big finger squeak and you wanted to get rid of that, you could kinda cheat it and push the level of the DI for a bar.” The large-diaphragm condenser and small-diaphragm condensers (in the XY configuration) were all cardioid and placed as close together as possible, roughly six to eight inches away from the guitar's 15th fret. The spaced pair was placed farther back and generally used more sparingly in the mix than the other mics.

Pickup Lines

Dodd and Way generally regard using a DI box to record acoustic guitar as a last resort to solve some sort of problem with the miked signal(s). Ahern and Newland see limited use for a DI signal when trying to achieve a creative effect. (See the sidebar “The Direct Route” for information on using DI boxes to record acoustic guitar.)

Dodd is adamant that a DI is useful “in a live situation only. It's such a ridiculous thing to put a DI on an acoustic guitar [in the studio],” he says. “You only do it when you have to. There are reasons to use a DI — in a live situation, it's very convenient and very controllable — but sound quality isn't one of them. It sucks. You don't need to use it, either.”

Way agrees with Dodd, saying he won't use a DI box “unless it's absolutely necessary. That's just not a sound that I particularly like.” When pressed to mention DI boxes he likes, Way countered that the last time he used one on acoustic guitar was “not in this decade.”

Ahern will use a DI box on acoustic guitar “only if the artist wants a special effect.” On one Emmylou Harris record, he recounts putting a Sunrise pickup on the acoustic guitar, boosting the signal with an old Music Man tube amp, and routing the amp's output to a spinning loudspeaker, in order to achieve a Leslie-speaker effect. When he must use a DI box, Ahern usually reaches for custom-built units. But he also notes that the API 512 preamp's instrument input “cannot be beat. It's often overlooked.”

Newland says that for a production that isn't “organic,” one option is to pan mic and DI tracks from the same recording pass opposite each other. “That gives you a pretty cool stereo effect,” he notes. When asked what DI box he could recommend, his response was that “for the money, the Countryman is one of the best DI boxes you can get.” He also lauds the Universal Audio 6176 Channel Strip as having “a great guitar direct input.”

Newland notes that the DI track can be a saving grace in some instances where bleed from a vocal outtake forces you to ditch a miked guitar track that was performed simultaneously. “There are times where the intention was for the voice and the guitar to go down at once, then you end up replacing the voice,” he says. “But there was something very cool about the guitar track, rhythmically, that was cut with the band. You still have the DI track. The music has to win out at that point.”

All four engineers stated that there was no difference in their approach to using a DI on an acoustic guitar fitted with magnetic versus piezoelectric pickups, with the exception that Ahern noted piezoelectric pickups usually require a healthy dose of EQ cut in certain frequency bands to sound decent. I have observed that the Demeter VTDB-2 Tube Direct box seems to load either type of pickup less than competing models (due to the VTDB-2's sky-high input impedance), resulting in the capture of a significantly wider range of frequencies. Also, musicians who are interested in using a DI with their Taylor guitar (300 Series model or higher) should check out the Taylor Expression System, which consists of three internally placed transducers and associated active electronics. It is by far the most natural-sounding DI system I have heard.

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SIDEBAR
THE DIRECT ROUTE
Most acoustic guitar pickups provide an unbalanced, high-impedance, instrument-level signal unsuited for direct interfacing with line-level gear such as a workstation I/O box, mixer, or A/D converter. A DI (or direct injection) box converts the pickup's unruly audio signal into a balanced, low-impedance signal that professional audio gear can handle with grace. While most direct boxes (or “DIs” for short) provide mic-level signals at their outputs (requiring connection to a mic preamp for additional gain boost), a few models feature onboard gain-boost facilities that bump up the output level enough for direct connection to line inputs.

Recording the output of an acoustic guitar's pickup with a DI box is easy: connect an unbalanced cable from the instrument's output jack to the DI's unbalanced input, and then patch the DI's balanced output into the input for an outboard mic pre, I/O box, console mic input, or A/D converter for routing to your recorder or DAW (see Fig. A).

If you are also using a mic or multiple mics to record the acoustic guitar, it's best to record each signal to a separate track so that you can independently (and perhaps dynamically) adjust the levels of the direct and miked tracks at mixdown. Be sure to delay the DI's track so that it is in phase with any miked tracks of the same acoustic guitar performance. It takes roughly 1 ms for the guitar's sound to reach a mic positioned 1 foot away. Delaying the DI signal by the same amount (1 ms for every foot the mic is distanced from the guitar) puts it in phase with the mic signal(s). Alternatively, DAW users can simply nudge the DI track later in time so that its waveform peaks line up with those for companion mic tracks. Aligning mic and DI signals in this manner reduces phase cancellations and comb filtering that would otherwise thin out bass frequencies and make higher frequencies sound less smooth.

For further information on using DI boxes, see “Direct Action” in the November 2001 issue of EM, available online at www.emusician.com.