Choosing the Right Mics

By definition, stereo miking requires a pair of microphones. Certain types of recording situations -- such as chamber orchestra, or an acoustic jazz trio -- demand extreme accuracy, and in these cases, it's highly desirable to have a matched pair of microphones. This means more than just two of the same model; it also calls for two mics that have been factory-certified to produce virtually identical frequency response. (Some, though not all, manufacturers sell matched-pair mics.)

Fortunately -- unless you're, say, capturing an audiophile-quality classical guitar recording -- you won't need a matched pair to record acoustic guitar tracks. In fact, you might not even need to use two of the same model of microphone (though if you do you'll get a more consistent timbre in each channel than if you had used two totally different mics). That said, rules are meant to be broken, so feel free to experiment by mixing and matching mic models. And like any musical instrument, every mic has its own sonic character, so try to get your hands on as many different models as possible and experiment.

Generally speaking, condenser mics are the right choice for acoustic guitar. As a group, they offer a far more detailed and realistic sound than dynamic mics. But before you choose a specific condenser, first decide what kind of sound you want. Small-diaphragm condensers (those with a diaphragm smaller than one-inch in diameter) generally offer a better transient response than their large-diaphragm cousins, producing a less colored, more detailed sound. For pop and country productions where guitar tracks will be tucked into dense arrangements with drums and bass guitar, small-diaphragm mics are often the best choice.

The AKG C480B, with a CK61-ULS cardioid capsule

Many engineers consider the AKG C480B ($987 with the CK61-ULS capsule), Neumann KM184 ($729) and DPA 4011 ($2,190) to be among the best small-diaphragm condensers on the planet. (All list prices are in US$.) All three sport cardioid (unidirectional) patterns -- meaning they tend to reject any sound that isn't directly in front of them -- and sound awesome on acoustic guitar. (Cardioid response is also required for most stereo miking techniques, in order for the resulting recording to have a "left-to-right" soundstage.) AKG's C480B is a modular mic, meaning that you can interchange various capsules -- each offering a different polar pattern -- with the mic body that holds the internal preamp. This mic features a 70Hz high-pass (low-cut) filter, useful for rolling off unneeded low frequencies when recording acoustic guitar.

A matched pair of Neumann KM184 mics

The Neumann KM184 exhibits an inherent low frequency roll-off at 200Hz, delivering guitar sounds free of low-end "boominess." DPA's 4011 mic -- known prior to 1998 as the Brüel & Kjær (B&K) 4011 mic -- features a 1dB roll-off in the midrange frequencies along with a 1dB rise between 10 and 15kHz. The result is a crisp, though not overly bright sound. This 4011 has treasured place in many mic lockers (including my own). Check out these links to hear the DPA 4011 on a Guild M20 acoustic guitar, with various mic placements.

A new DPA 4011 (found in many mic lockers as the former B&K 4011)

There are plenty of other small-diaphragm, cardioid condensers on the market, many of which offer decent performance for a lot less scratch. Some better-known alternatives that other enginneers report good results with include Shure's SM81 ($530), AKG's C1000S ($297), and Audio-Technica's AT3528 ($259).

Large-diaphragm mics -- those featuring diaphragms at least one inch in diameter -- can also provide outstanding results when recording acoustic guitar. All other things being equal, these mics tend to offer a slower transient response than their small-diaphragm counterparts. This causes a slight de-emphasis in high-frequency detail and tends to give them a rounder, warmer sound -- just the ticket for traditional jazz recordings and lean guitar/vocal arrangements. (It's this warmth that makes large-diaphragm mics so popular with vocals.) The Lawson L47MP Tube Condenser ($1,995) sounds great on acoustic guitar for these applications. I've also used the Manley Reference Gold Tube Condenser ($5,500) with excellent results.

Lawson L47MP Tube Condenser

Manley Gold Reference Tube Condenser

On a budget but craving that large-diaphragm condenser sound? Some candidates that I didn't have the chance to work with would include AKG's C414B/ULS ($1048), Neumann's TLM103 ($995), the Alesis AM51 ($549), and the AKG C3000B ($478).

And what about a dedicated stereo microphone? These mics -- such as Shure's VP88 ($1194) and Audio-Technica's AT825 ($525) -- typically have a pair of cardioid capsules mounted in one housing. While they may be useful in certain applications, they're actually less flexible than a pair of independent mics -- since their diaphragms are physically fixed relative to one another. In other words, if you want to try some of that mic-above-the-bridge, mic-above-the-fingerboard stuff, or any other interesting variations, you'll want a pair of mono mics.

Next Page: Mono-Compatibility, EQ & Compression....