Recording the acoustic guitar can be a bit difficult until you know a few tried and true techniques. Live2Play is here to help.
By Darth Fader for the Live2Play Network
Guitar aficionados know that the body of a guitar acts as an amplifier for the strings, and that guitar tone is affected by size, shape, internal bracing, type of wood and the player’s choice of strings. The sound also changes depending upon whether the player uses a pick or their fingers. A pick generally creates a brighter and louder sound, while fingerpicking tends to be lower in volume with less attack. Ideally a recording of an acoustic guitar captures all of these elements.
When getting ready to record acoustic guitar ask yourself a few questions: Is this guitar a featured or solo instrument, or is it a support instrument? Does the guitar need to share the mix with vocals and/or other instruments? Does the musician play the instrument softly or loud, strummed or finger-picked?
The answers to these questions can help you decide how to approach the recording. If the guitar is the only instrument, then you can record it in stereo and make it sound big because it does not need to leave space in the mix for anything else. If the guitar needs to fit into a recording along with a lot of other instruments, then you probably don’t need as much low end: the lows will only clutter the mix. You’ll especially need to pay attention to the low-mids if there is an acoustic piano in the mix because these two instruments can “mask” (interfere with) each other. If the recording is guitar and voice only, you can give the guitar more ’weight’ before it steps on the vocal. Double-tracking an acoustic guitar (playing the same exact part a second time) produces a thick, beautiful sound (sort of like the ultimate chorus), but you want make sure it’s not so thick that other instruments get buried. When recording a quiet, finger-picked guitar, you’ll need a quiet place to record, microphones with low “self-noise” (meaning they don’t generate a lot of noise), and preamps with a high signal-to-noise ratio. Sorry to say, this usually translates into “expensive.”
Mic Placement and Number of Microphones
When I record an instrument for the first time I spend a few minutes listening. As the musician plays I move my helmet to different positions on the guitar so I can get an idea of where the instrument sounds best. This is difficult when you are working alone. You might be able to get a friend to play the guitar while you listen, but your touch will be different than theirs so the tone will vary. The alternative is to make a test recording. Play a few bars, then move the mic to a different area of the guitar and play again. You can speak the position of the mic as you make the test recording (“now the mic is in front of the bridge, pointing directly at the top”). Listen back to the recording, use the microphone position that sounds best to you as a starting position, then tweak it. Microphone selection and placement is almost as important as the person who is playing. There are no rules and experimentation should be part of the process — but we can furnish a few suggestions.
Acoustic guitars tend to produce most of their low frequencies from the sound hole. Placing a microphone in front of the sound hole usually produces a boomy sound with excessive lows, often to the point of being muddy. On the other hand placing a microphone near the bridge is likely to give you a bright, thin sound with a lot of articulation but not a lot of roundness. One position that works almost universally well is with the mic located ten to twelve inches in front of the 12th fret (or where the neck and body meet), aiming toward the sound hole. The photo shows a microphone in this position. This works great with small diaphragm condenser microphones such as a Shure PGA181 or SM81, Audio-Technica AT4041 or ATM450, or Audix SCX1. The photo (top) shows a Sony C535 that was given to me by the Emperor when I graduated the Jedi Academy, but you’d be surprised at how good a Shure SM57 will sound in this application.
This technique delivers a good balance between the attack from the pick on the strings and the warmth and roundness of the body. Depending upon the player and the type of strings they are using you may get too much fret noise so you’ll have to give it a try and listen to the results. If you find that there is not enough body to the sound, either move the mic up the fretboard toward the neck/body joint, or point the mic more toward the sound hole. As you move the mic toward the headstock, the sound will thin out and the volume will drop drastically because as you may know — there isn’t a lot of sound being produced by that part of the guitar.
A Few Words on Microphones
Microphones can be designed to capture sound equally from all directions (this is called omnidirectional), or they can favor sound coming from in front of the mic (this is known as cardioid). They can even favor sounds coming from in front and back but reject sound coming from the sides of the microphone (this is known as figure-eight or bidirectional). There are other directional characteristics but omnidirectional and cardioid are the most popular. The shape or appearance of a microphone has little or nothing to do with the manner in which it picks up sounds. For example a Shure SM58 has a round ball at the business end but it does not capture sound from all directions.
When you move a directional mic very close to an instrument or voice (within a few inches), you get something known as proximity effect. Proximity effect is an unnatural boost in bass frequencies. Radio personalities use this to make their voices sound fatter by putting the their mouth right on the mic grill. If you place a directional mic very close to an acoustic guitar you might get too much low end — particularly when you are near the sound hole. To reduce this, move the mic away from the instrument. Usually proximity effect disappears once the mic is moved ten to twelve inches away from the instrument. On the other hand if you find that the tone is thin, move the mic closer to take advantage of proximity effect. Omnidirectional mics generally do not produce (or produce very little) proximity effect so you can move them much closer to the guitar without bulging bottom(!).
Another approach to recording acoustic guitar involves placing the microphone at or near the ear level of the guitar player as shown in this photo. This microphone (Shure KSM44) has an unusual appearance. It may look like the mic is pointing toward the right but it is not. It is pointing straight down toward the floor. Remember: the appearance of a microphone has nothing to do with the manner in which it captures sound. This mic placement is not as tried-and-true as the first. In some cases it can create a startlingly realistic sound — much like what you hear when you are playing, but this depends upon the guitar, the player and room.
Some engineers and guitar players like to use more than one microphone on a guitar either for the purpose of recording in stereo, or for getting different tones from different areas of the guitar and then adding them together. We’ll leave stereo recording for another time and discuss the idea of using more than one mic at the same time. The most focused sound you can get will come from one microphone. Sometimes adding a microphone decreases clarity by creating phase cancellation. This is a type of interference that happens when signals from multiple microphones are combined. Certain frequencies may be over emphasized and other frequencies may disappear. For example you could place a microphone pointing at the 12th fret and another mic facing the bridge of the guitar. If you hear certain frequencies disappear when you add the two mics, then you have phase issues; move one of the microphones to a different position. Of course feel free to experiment — my general rule of thumbs is… if it sounds good, then it is good.