9. FAQ

It depends on your miking technique. A lot of engineers put one microphone in front of the guitar directed at the neck joint and another directed at the bridge. Strictly speaking, this is not a “real” stereo technique but multi-miking. You’re miking two points of an instrument that inherently produce different sounds. Since the two mics will pick up different sounds, anyway, it doesn’t matter much if the two mics aren’t matched. In fact, you can use two different mic models, provided the result is pleasing subjectively. However, you do have to use a matched stereo pair for true stereo miking techniques such as XY or ORTF.

If it is a high class mic from one of the more expensive brands, you can buy another mic of the same type. The leading manufacturers (i.e. European brands of long tradition) produce microphones to very tight tolerances. Two randomly selected microphones of the same type will be close enough for any but the most critical applications. If you plan on making classical recordings for a record label, you better get a matched pair. For less critical uses, a non-matched pair will do just fine. Among inexpensive small diaphragm mics, using a selected pair is highly recommended. Inexpensive brands cannot afford to work to tolerances as tight as the renowned European brands; moreover they often change internal components without notice. So selection/matching is required in order to obtain a true and symmetrical stereo image.

That’s mostly a matter of taste. Also of looks ;-) There is no compelling technical reason. In fact, many vocalist condenser microphones for stage use are small diaphragm microphones. In the studio, engineers like to use large diaphragm microphones, because their particular sound characteristics have a flattering quality. They make voices sound smooth, expensive, and larger-than-life. Big size mics also make the vocalists feel important, which sometimes helps to get a better performance. Nonetheless, small diaphragm condensers can produce excellent results in documenting a voice exactly as you hear it. Classical singers are often recorded using small diaphragm microphones.

Small diaphragm condensers are a safer choice. In almost all cases you will get good or excellent results. With large diaphragm microphones, it depends on the model. Some are excellent, especially if you’re aiming at a full, “larger-than-life” sound. Other large diaphragm microphones are too much geared towards vocal recording to produce satisfying results on acoustic guitar. As always, try things out yourself and use whatever sounds good to your ears. There are no fixed rules.

Omnis are very different than cardioids. You can place omni mics very close to the source – there is no proximity effect, so you won’t get that boomy sound you’d get with a cardioid mic so close to the source. For stereo recordings, you can’t use techniques that require the mics to be very close to each other. XY-stereo miking won’t work. Remember that omnis pick up sound from all sides equally. They don’t record any directional information. The most common stereo technique when working with omnidirectional microphones is “spaced omnis”, i.e. the two mics face the sound source and are spaced depending on the size of the sound source and the distance between the mics and the sound source. For acoustic guitar, the distance between the mics should be roughly between 6 and 12 inches (15-30 cm). A large choir or an orchestra may require wider spacings. Listen critically and make sure there is no hole at the centre of the stereo image.