String Theories IT DON'T PHASE THEM
Some of the most innovative guitarists in the world -- and the engineers who record them -- share their scientific, artistic, psychological, and sometimes complex approach to capturing a good acoustic guitar sound. It's an often painstaking and complicated process. And you thought all you needed was a mic and recording machine. Oh, if only it were that simple!
The concept of stereo and multiple miking an acoustic instrument to provide proper sonic perspective is a tried-and-true technique. Yet, walking hand-in-hand with this method is the baffling issue of phase cancellation: the single most mysterious obstacle facing an engineer.
Peter Ostroushko's Postcards: Travels with a Great American Radio Show is a mix of Americana, European folk, blues, jazz, and rock, and showcases Ostroushko's sharp, percussive mandolin attack. When I recorded Peter, I used different types of microphones in close proximity to each other -- phase checking was very important," explains engineer/mixer Matthew Zimmerman. All of Peter's tracks were recorded stereophonically with stereo mics. Sometimes I use a single point stereo mic in X/Y or mid/side. Often I will augment this pair with a large diaphragm condenser, such as a Neumann M 149 in omni. Again, I check the phase against the main pair. (Each mic needs to have its phase checked against the others.) I love omni with acoustic instruments because they put air into the sound. I am constantly inverting the phase on my console and summing to mono to see if I get more or less bass. If you get more low end, you are usually in phase."
You might try starting with a placement such as spaced cardioids, back maybe 12"-14" or so, pointed roughly at the spot where the neck joins the body, and the second mic pointed at the bridge from various angles, depending where it sounds the best," notes producer/engineer Neal Harris, who recorded Alex de Grassi's stunning Now and Then and The Water Garden. Don't just pull out of the how-to-record cookbook. Set up mics and listen, listen, listen."
You have to move [the mics] around until you have pretty good phase coherency and then listen to the microphones in the relative balance," confirms producer/engineer Steven Miller, who shaped the big," hyper-real acoustic sound of many of the instrumental Windham Hill Records (i.e., Michael Hedges' 1984 breakthrough Aerial Boundaries).
Singer/songwriter John Gorka's description of his record Writing in the Margins as a quietly subversive search for hope" sums up producer/engineer/mixer Rob Genadek's approach to inconspicuously capturing Gorka's rich voice and acoustic guitar playing -- without sacrificing character or clarity. John uses a Lawson L47 tube vocal mic," says Genadek. Then we used two Neumann KM184s, one near the neck and one near the bridge [of the acoustic], somewhere near the body. That one ends up sounding mid-rangy but it fills in all the stuff that the other one misses. John doesn't get real close to the vocal mics, so there is quite a bit of guitar in the vocal mic . . . it becomes a matter of getting his voice right, then working with the other mics to place them in the right position to ensure that the phase characteristics are all complementary among the three. You can move a microphone an inch this way or that way without affecting the sound it captures too much, but when it is combined with another [mic], it can be a drastic change. How do you fix it? You move the mic, obviously."