Recording Acoustic Guitar

In this blog, I'm going to show you how to record an acoustic guitar focusing on a few of my preferred techniques.

Recording an acoustic guitar can be quite challenging and having received numerous requests for help from friends regarding the recording of their instruments, I wanted to get the information and techniques down in this tutorial to show you how to record your acoustic guitar properly.  

The first thing to mention about the acoustic guitar is that despite sharing approximately the same fundamental tonal range as its electric counterpart, E2 to C6/D6 on 20/22 fret instruments respectively; the overall frequency range produced by the acoustic instrument is much wider; electric guitars being limited by their pickup, amplifier and speaker design. Typically the electric guitar exhibits few frequencies above 5khz, whereas the acoustic instrument produces frequencies that can happily exceed 10khz, producing a complex array of harmonics and overtones that contribute much to the instrument’s timbral character. It is therefore vital to choose the correct microphone for the job.

Condensers are usually the mics of choice when recording acoustic guitar as they capture a wide range of frequencies, are moderately flat across the frequency spectrum from 20hz to 20khz and are much more sensitive than dynamic designs. So abandon your trusty SM57 for this task.

I’ve found through experimentation that small-diaphragm designs work better than the larger capsule offerings as they behave a little better off-axis and are easier to place discreetly in front of the guitar. Recently I’ve been using a pair of Rode NT5s, which are a pencil design and have a cardioid polar pattern. However, I’ve had fabulous results with the famous Neumann KM184 and AKG C451s. As you can see from the photograph below I’ve got the mics in their elastic suspension mountings. This radically reduces any mechanically transmitted vibrations travelling through the mic stand, ensuring that the recording is as clean as possible. If your mics didn’t come with suspension mounts you can always purchase a universal type that should work just as well.

If you’re unsure about the term cardioid or the various properties of different microphone polar patterns you might want to buff up your knowledge by clicking here.

So now you’ve got the mics where do you put them?

Most of the problems recording an acoustic guitar begin with trying to mic the sound hole. I’ve heard many examples of this method but have never obtained a balanced recording using this technique. The frequencies emanating directly from the sound hole don’t accurately represent the complex array of frequencies that constitute the overall timbre of the instrument. You may have noticed from your own guitar that many of the high frequencies seem to come from the neck and face of the instrument. Indeed if you listen carefully you’ll find all sorts of resonant areas other than the sound hole. So let’s rethink miking the instrument at the sound hole.

Mono Recording

 Now, what I’m about to suggest might sound a bit weird but if you haven’t tried this before, take a leap of faith and trust me. You won’t regret it!

You’ll want to position the mic at a working distance of between 6″ to 10″ from the top shoulder of the guitar just above where the neck joins the body, this is usually on fret 14 for modern steel string instruments. The further back the mic is from the guitar the more “room” sound you’ll be capturing, conversely the closer the mic is to the source the less room sound will be captured. It’s really important to keep in mind when working with any directional mic, the “bass proximity effect” that occurs in close mic situations. That is, the closer the mic gets to the source the more exaggerated the bass frequencies become. So try to resist the temptation to mic the instrument too closely if you want to maintain a natural, balanced recording.

I would suggest starting with the mic on axis facing the guitar and making a series of recordings as you progressively move the mic off axis. It’s possible to obtain more bass frequencies by angling the mic towards the sound hole and brighter frequencies by angling the mic along the neck of the guitar. Proceed methodically and take notes of where the mic is for each test recording that you make. This way you can review your recordings to find the mic position that really works for your instrument and room.

Stereo Recording

 If you want to progress to a stereo technique it’s actually quite a simple process and can work wonders in post-production!

I’ve always favoured the XY coincidental (intensity-dependent) stereo technique for acoustic guitars over a spaced pair configuration as the phase coherence is much better. Although I’ve also had great success with the less commonly used MS setup. I do want to write a blog concentrating on MS as I think it has much to offer but is beyond the scope of this tutorial.

Before I continue if you are unfamiliar with stereo mic techniques or the term phase you’ll want to click here.

For this stereo technique you’ll need two mic stands an XY mic clip or a stereo mounting bar and a matched pair of mics. Our first task is to position the mic capsules between 90 and 130 degrees to one another so that they are overlapping forming a cross. The central point between the two mics should face the guitar at roughly the same working distance as before and aim towards the top shoulder of the instrument. The mics need to be panned hard left and right for the stereo image to become apparent.

It’s still important to observe the same working methodology as for the mono mic technique to obtain a natural, balanced stereo recording.

The XY stereo technique offers some great advantages over the mono version. In post-production it allows the guitar to sit at the edges of the mix, clearing the centre of the stereo image for vocals or lead instruments. It’s also very mono-compatible and as such translates well to small speaker systems with limited separation between speakers or mono systems… yes they still exist!

Below is a photo illustrating a similar XY configuration but this time using a stereo mounting bar. I find that this is very useful as it eliminates the need for two mic stands.

In conclusion here’s an example of a nylon-strung, classical guitar recorded with the above stereo technique. I’ve applied some compression to bring out the inner detail and processed the recording with EastWest’s Spaces reverb plugin.

I hope you find the information useful and if you need any assistance or more information please leave a comment.

Good luck with your acoustic guitar recordings.

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