Microphone Placement Techniques: Guitar
David Miles Huber
The following sections describe the various sound characteristics and techniques that are encountered when miking the guitar.
The popular steel-strung, acoustic guitar has a bright, rich set of overtones (especially when played with a pick). Mic placement and distance will often vary from instrument to instrument and may require experimentation to pick up the best tonal balance. A balanced pickup can often be achieved by placing the mic (or an X/Y stereo pair) at a point slightly off-axis and above or below the sound hole at a distance of between 6 inches and 1 foot (Figure 4.46). Condenser mics are often preferred for their smooth, extended frequency response and excellent transient response. The smaller-bodied classical guitar is normally strung with nylon or gut and is played with the fingertips, giving it a warmer, mellower sound than its steel-strung counterpart. To make sure that the instrument’s full range is picked up, place the mic closer to the center of the bridge, at a distance of between 6 inches and 1 foot.
Miking Near the Sound Hole
The sound hole (located at the front face of a guitar) serves as a bass port, which resonates at the lower frequencies (around 80 to 100 Hz). Placing a mic too close to the front of this port might result in a boomy and unnatural sound; however, miking close to the sound hole is often popular on stage or around high acoustic levels because the guitar’s output is highest at this position. To achieve a more natural pickup under these conditions, the microphone’s output can be rolled off at the lower frequencies (5 to 10 dB at 100 Hz).
Surround Guitar Miking
An effective way to translate an acoustic guitar to the wide stage of surround (if a big, full sound is what you’re after) is to record the guitar using X/Y or spaced techniques stereo (panned front L/R) … and pan the guitar’s electric pickup (or added contact pickup) to the rear center of the surround field. Extra ambient surround mics can also be used in an all-acoustic session.
The Electric Guitar
The fundamentals of the average 22-fret guitar extend from E2 to D6 (82 to 1174 Hz), with overtones that extend much higher. All of these frequencies might not be amplified, because the guitar chord tends to attenuate frequencies above 5 kHz (unless the guitar has a built-in low impedance converter or lowimpedance pickups). The frequency limitations of the average guitar loudspeaker often add to this effect, because their upper limit is generally restricted to below 5 or 6 kHz.
Miking the Guitar Amp
The most popular guitar amplifier used for recording is a small practice-type amp/speaker system. These high-quality amps often help the guitar’s suffering high end by incorporating a sharp rise in the response range at 4 to 5 kHz, thus helping to give it a clean, open sound. High-volume, wall-of-sound speaker stacks are less commonly used in a session, because they’re harder to control in the studio and in a mix. By far the most popular mic type for picking up an electric guitar amp is the cardioid dynamic. A dynamic tends to give the sound a full-bodied character without picking up extraneous amplifier noises. Often guitar mics will have a pronounced presence peak in the upper frequency range, giving the pickup an added clarity. For increased separation, a microphone can be placed at a working distance of 2 inches to 1 foot. When miking at a distance of less than 4 inches, mic/speaker placement becomes slightly more critical (Figure 4.47). For a brighter sound, the mic should face directly into the center of the speaker’s cone. Placing it off the cone’s center tends to produce a more mellow sound while reducing amplifier noise.
Isolation cabinets have also come onto the market that are literally sealed boxes that house a speaker or guitar amp/cabinet system, as well as an internal mic mount. These systems are used to reduce leakage and to provide greater control over instrument levels within a recording studio or control room during a session.
A DI box is often used to feed the output signal of an electric guitar directly into the mic input stage of a recording console or mixer. By routing the direct output signal to a track, a cleaner, more present sound can be recorded (Figure 4.48a). This technique also reduces the leakage that results from having a guitar amp in the studio and even makes it possible for the guitar to be played in the control room or project studio. A combination of direct and miked signals often results in a sound that adds the characteristic fullness of a miked amp to the extra “bite” that a DI tends to give. These may be combined onto a single track or, whenever possible, can be assigned to separate tracks, allowing for greater control during mixdown (Figure 4.48b). During an overdub, the ambient image can be “opened up” even further by mixing a semidistant or distant mic (or stereo pair) with the direct mic (and even with the close miked amp signal). This ambient pickup can be either mixed into a stereo field or at the rear of a surround field to fill out the sound.
Figure 4.48 Direct recording of an electric guitar: (a) direct recording; (b) combined direct and miked signal.
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Excerpt from Modern Recording Techniques, 7e by David Miles Huber and Robert E. Runstein © 2009 Taylor & Francis Group. All Rights Reserved.