Recording Outside the Box

Jun 14, 2005 6:21 PM, By Pat Kirtley

           
 

FIG. 2: Using a pair of condensers in conjunction with a magnetic pickup can give you a big sound. At mixdown, try panning the condensers right and left and putting the magnetic pickup's output up the middle.

You can get effective guitar tones by combining standard mic configurations with the output of an onboard guitar pickup. For steel-string acoustics, use the classic condenser-mic pair augmented by a magnetic pickup placed in the sound hole. For years I kept a Bill Lawrence snap-in magnetic in a studio drawer just for that purpose. Most engineers and musicians consider such a pickup by itself unsuitable for recording — it has that characteristic electric-sounding one-dimensional tone that you love to hate in an acoustic. But consider its good qualities, such as rock-solid bass response and extra sustain.

Typically, you record the stereo mic pair on two tracks and the pickup on its own third track. During mixdown, you can refine the blend in a number of ways. One is to EQ away the upper mids and highs from the pickup and remove the bass frequencies from the mic pair at the same time, giving you the microphone equivalent of a two-way crossover. A typical panning scheme is mics full left and right, and pickup centered (see Fig. 2). The result? A “bigger than life” acoustic sound that's perfect for situations in which the guitar is prominent in the mix (see Web Clip 1). In this scenario, I generally use about 75 percent mic sound and 25 percent pickup sound. A useful bonus is that the onboard pickup is relatively isolated from outside acoustic sounds. If low-frequency rumble in the ambient environment is a problem, such a setup is part of the cure.

Standing this notion on its head, wonderfully spacious sounds materialize when you mic the body of an electric guitar. Even solidbody electrics radiate considerable high-frequency acoustic energy directly from their bodies — airy tones that are entirely lost through the guitar's normal pickups. Hollowbody archtops have an even bigger acoustic tone. The trick is to mic the guitar as if it were an acoustic, and then blend the mic sound with the usual mic-in-front-of-amp tone. No matter the type of guitar or the playing style being recorded, this idea is worth trying in your quest for capturing unique guitar sounds. It's amazingly easy, and there are no critical parameters — simply stick the mic out there and find a blend. Usually, just a little of this acoustic sound will add clarity and dimension.

You can pay big bucks for a laboratory-matched pair of microphones, complete with paperwork to confirm their common source of electrical DNA. It's a starting point for many classic techniques for recording acoustic guitars. The idea is to create a spacious, balanced stereo field. That's great for audiophile recordings of solo guitar, but a technique that offers far more possibilities is to use two completely different mics. For instance, try putting a small-cap condenser up by the neck and a dynamic down by the lower body. When the tracks are panned fully left and right, the stereo perspective is greatly exaggerated, and sometimes that is exactly what you want (see Web Clip 2).

I once got a luscious, fat sound with an AKG C 451 B on one side and a Shure ES615 omni “room-equalization” mic on the other. Similarly interesting results can be had with a large-diaphragm tube mic on one side and a dynamic cardioid “stage mic” on the other. A caveat: pay attention to potential phasing problems between extremely dissimilar mic pairs.

Directional microphones were developed for good reasons, the main one being focus, or the directional admittance of desired sounds and rejection of unwanted ones. Most of the microphones used in studio work are directional types — cardioid, supercardioid, or bidirectional (figure-8). The ability to reject unwanted sound comes at a cost, and one of the liabilities is the proximity effect: whenever a directional mic is placed close to the source, bass frequencies are overemphasized. That can be a significant problem when recording acoustic guitar, especially if you want to position a mic anywhere near the sound hole.