There are as many ways to mic an acoustic guitar as there are engineers in the world.
I want to show you why you should consider stereo-miking acoustic guitars (that is, using two microphones on the guitar instead of just one), and then offer reasons not to do it.
A lot of engineers will throw a single mic on an acoustic guitar, point it at the 12th fret, and hit record.
While there’s nothing wrong with this, I think a lot of people are missing out on some very cool guitar tones.
With that in mind, here are three reasons to stereo-mic an acoustic guitar.
1. It adds width to your guitar-vocal demos (or solo acoustic guitar).
If you’ve recorded a basic guitar-vocal demo using one mic on guitar and one on vocal, you’ll notice that while the recording may sound great, it can be very narrow, very mono. You can play around with reverb plugins to add some space and width, but acoustic guitar rarely sounds all that good (or natural) through a reverb.
One technique a lot of engineers will use is to slightly pan the mono guitar track to the left or right, creating some separation between the guitarist and the vocalist. This may help a bit, but it still comes off sounding very mono.
There’s nothing wrong with mono. But having that extra width may make your demos stand out from the rest of the mono crowd.
2. It captures the entire instrument.
If you were to mic up a big Steinway grand piano, would you use one microphone? Of course not. It’s a big instrument, and it would take at least two if not four or six microphones to adequately capture the sound.
The same holds true with acoustic guitar. The tone of the guitar is spread out over the entire instrument. If you stick a microphone three inches from the 12th fret, you may get a nice sound, but you’ll only be taking a snapshot of a small portion of the guitar’s overall sound. You won’t be capturing the sound of the guitar as it was meant to be heard – as a whole.
As you may know, if you place a microphone along the neck, you’ll get a lot of high-end. If you place the mic down below the bridge, you’ll get a lot of bottom end. Each one by itself gives a bit of a misrepresentation of the guitar as a whole, but when combined you get a very full-sounding acoustic guitar track.
3. It allows you to place the mics closer to the instrument, picking up less noise.
Noise is one of the biggest issues we face. While it would be nice to place the microphone four feet away from the guitar, that’s simply not possible in many situations. AC noise, computer noise, neighbor noise, traffic noise — they all come into play.
The beauty of stereo-miking the acoustic guitar is that you can place the microphones right up on the instrument.
For example, this past weekend I spent a lot of time recording acoustic guitar. I had one microphone above the bridge, angled inward. The second microphone I placed at around the 6th fret, angled inward. Both mics were roughly 4 inches from the guitar.
Because the mics were so close to the guitar, they picked up more of the guitar’s sound and less of the room noise. Also, because I had two microphones, I didn’t sacrifice tone, since I was picking up both the lows (with the first mic) and the highs (with the second mic).
The end result was a huge acoustic guitar sound with minimal noise.
Stereo-miking acoustic guitars isn’t for everyone, nor is it for every guitar or song or recording. However, if you’ve not given it much thought, try it next time you record acoustic.
Audio Samples
I’ve got four samples for your listening enjoyment. They’re mono and stereo recordings of the same performance. Listen to the mono version first, then listen to the stereo.
With the mono tracks, you’re listening to the single microphone along the neck. It doesn’t sound bad at all, but then when you add the second microphone, a fullness enters the mix. These are dry tracks with a bit of EQ, but no other effects or compression. (And they’re all 16-bit WAV files.)
The Other Side
Now, for three reasons not to stereo-mic an acoustic guitar.
1. The guitar is cheap (or just doesn’t sound all that great.)
For several years I owned a fairly cheap Ibanez acoustic guitar. It didn’t sound awful, but it didn’t sound great. It was made out of a wood laminate and was lacking in the low end.
I tried recording that guitar with two mics, but it never gave me a much better sound.
If you think about it, it makes sense. One of the main reasons I proposed for stereo-miking acoustic guitar was the fact that it allows you to capture the entire instrument.
However, if the entire instrument doesn’t sound all that great, capturing more of the instrument won’t help.
In case you’re wondering, I was still able to get a decent recording out of that Ibanez. I used the proximity effect to my advantage. I would place a large-diaphragm condenser a couple inches from the 12th fret. The recording ended up having much more low end than the guitar itself normally had.
If you’re attempting to record a cheaper acoustic guitar, spend some time with a single microphone, find a “sweet spot,” and go from there.
2. You don’t want to deal with phase issues.
Since sound waves travel at a certain speed, any time you place two microphones on one source, there’s a chance that the sound waves will reach each microphone at a slightly different moment in time.
Any time this happens, the two tracks you’re recording are slightly out of phase, causing comb filtering to occur. There are technical charts and graphs out there that explain this in-depth.
However, what basically happens is the guitar sounds thin. Each microphone by itself may sound great, but when the two are played together, the guitar suddenly lacks depth and clarity.
It’s the same concept used in a phaser/flanger guitar pedal. The pedal delays the signal a bit and blends it with the original signal, causing that thin “phasey” sound. This sounds great on electric guitar, but it’s usually not what you’re looking for in acoustic guitar.
The way to avoid this is to make sure the two mics are an equal distance from a single point on the guitar. This is easier said than done, since guitarists are notorious for moving around from take to take, which could potentially add to the phase issues.
If you’re spending a lot of time getting the mics to play well together, then it may be time to go with a single mic and get back to recording.
3. The acoustic isn’t a prominent instrument in the song.
If the acoustic guitar is the central instrument of a song — perhaps in a singer-songwriter demo — then it makes sense to have that guitar be as big as possible.
However, if you’re working on a huge session, many times the acoustic guitar becomes a very small part of the overall mix. If you listen to a few songs on the radio, you’ll hear that the acoustic guitar oftentimes sounds very light and thin.
In these situations, since the acoustic is going to be heavily EQ’d and buried in the mix, it won’t make any difference to stereo-mic the guitar. Save yourself some time (and hard drive space) and just use a single microphone.
Joe Gilder is a Nashville-based engineer, musician, and producer who also provides training and advice at the Home Studio Corner. Note that Joe also offers highly effective training courses, including Understanding Compression and Understanding EQ.
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