Music production aficionado Dave Chrzanowski looks at the microphone types, placement and specs required for successfully recording your acoustic guitar
Let’s not beat around the bush. There are many instruments and lots of different microphones we could discuss in this article. However that article would quickly turn into a book, so let’s narrow the subject matter down. Today we are going to discuss how to mic an acoustic guitar. Why? Well, most songwriters own one, and those interested in producing will certainly come across a few throughout their recording career.
Where to place the mics
Rule number one: don’t place the microphone up close to the soundhole. This is where most novices get caught out as it seems like the most obvious place to put a microphone. However, the soundhole is where the low frequencies are produced and will leave you with a boomy, bassy sound, referred to as the Proximity Effect – not good. The best sound comes from the guitar’s soundboard and this is the area you want to target.
If you want to highlight some of the guitar’s bass frequencies then place the microphone 12-16 inches away from the soundhole. Odds are you’ll want to capture a mixture of the guitar’s frequencies and natural sounds. So for balance, try pointing the microphone in the direction of the 12th fret, as this will pick out fret noise and will sound more natural.
If it’s a softer attack with an emphasis on tone you are after, then place the microphone lower between the bridge and the corner of the body. But if a powerful sound with more bass is required then do the opposite and raise the microphone above the bridge. That leaves the mid-range frequencies. If you want to get to those then place your microphone at the bridge; this is also good for slide guitar. Having the microphone at the bridge means less string and fret noise but more plectrum sounds.
It’s unlikely you’ll be reading this sat at the helm of your very own top of the range recording suite. You’re in your house or flat. But either way understanding a recording environment is important in achieving the best sound.
Adding a touch of reverb and ambience will inject some life into the recording. A bathroom will probably have too much of both, whereas a living room will be more ideal as the furniture will soak up frequencies providing a damper sound.
One method of getting the best sound from an acoustic guitar is to record it in stereo using the XY technique. But be prepared for any phasing issues that will occur. What is phasing? Phasing is time differences when two signals (sounds) are added together. In this case, positioning two microphones on an acoustic guitar will create a delay between the recorded sounds, even though they are from the same source recorded simultaneously. This will result in a sound that is flat or dull. It’s always best to eliminate phasing at the source by placing microphones correctly before recording. Although there are steps in the early mixing stages to combat phase, like flipping the polarity, this won’t always work.
The Behringer C-2 condenser microphones are ideal for this recording technique. The name XY comes from the shape the microphones make. So, you have two options, placed apart in a Y-shape, or across each other in an X-shape.
There’s a lot more science and terminology surrounding phasing, like comb filtering, but that’s an article in itself.
Like all things tech, there are lots of terms and jargon. Different microphones have varying frequency responses. Some handle solo instruments and vocals well, while others are designed more specifically, like the AKG D112 kick drum mic. Below are a few terms explained:
Cardioid: Picks up sound with high gain from front and sides, but poorly from the rear. So-named as their directional sound pick-up is heart-shaped. Example: Shure SM57B
Condenser: Are multi-purpose and good for budget. Are designed for close miking of vocals and solo instruments due to having poor bass frequency response. Examples: Røde NT1-A, Shure SM86, Behringer C-2
Dynamic: Comes in two categories, moving coil and ribbon – ribbon microphones have a figure-eight pickup pattern, meaning they pickup from front and back but not the sides. Like condensers, they have a boost around the mid-range frequencies. Dynamics have a higher noise floor, so its natural hiss can be noticeable on recordings. Good for a lo-fi sound, not necessarily a true reflection of the guitar’s natural sound. Examples: Shure SM57, Shure SM58
Diaphragm (large and small): If a microphone has a large diaphragm (one-inch) it will make the source of sound much bigger, for this reason, they are often used for vocals and solo instruments. Examples: Røde NT1-A, Shure SM57B, Neumann TLM 102
Whereas a small diaphragm (half-inch) condenser microphone will better reflect the natural sound of an instrument. A good place for this microphone if recording acoustic guitar is 16 inches away from the guitar, pointing towards the soundhole and the picking hand. Examples: Shure SM58, Behringer C2
So that leaves us with one question. Which microphone is best to use when recording an acoustic guitar? And the answer is it’s down to taste. Whether you want a clean, crisp sounding guitar or a dirty low-fi muddy gloop, remember the microphone is documenting the natural sound of the guitar it is recording. To get the most from the guitar make sure the strings are fresh and are in tune.