Recording the Acoustic Guitar: The Basic Rules

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While recording an acoustic guitar might sound like a straightforward job, getting a clear and natural-sounding recording can depend on a number of factors. The kind of microphone you use, the way the microphone is positioned, as well as the way the recording space reacts to the vibration of the strings, all play an important role in the final recording. All of these variables make recording an acoustic guitar at home a particularly tough job, but as long as you remember the basic rules that follow in this blog, after a little experimentation, you’ll be able to lay down some great-sounding demos with an acoustic guitar, and all in the comfort of your own home.

Vibrations

An acoustic guitar produces sound via vibrating strings, and these vibrations resonate throughout the entire body of the instrument so that the resulting sound is acoustically amplified. Most of the sound is ‘held’ inside the body and released through the soundhole (the opening in the soundboard). It’s at the soundhole that the sound of a guitar is most full and loud, but that doesn’t mean that it’s the best place to put a microphone. The sound of the guitar will sound slightly different from different positions, and this can largely depend on the model as well, so if it’s a dreadnought, concert, jumbo, a smaller-sized parlor, or a classical guitar with a plastic back (an Ovation), each guitar will produce its own specific quality of vibration and sound, and each guitar will have it’s own ‘sweet spot’: the optimum position for a microphone. The perfect position is completely subjective, but won’t be the same for every guitar, so you’ll always need to experiment a little to find it. More experienced sound engineers will have developed some good intuition when it comes to finding the sweet spot, but for a complete novice, it can be a difficult journey. In any case, you won’t find it directly in front of the soundhole, where the sound is simply too loud, the balance is too far off and the bass might just drown everything out completely. Be patient and listen to the guitar from various angles until you can hear where the tone is the most balanced – so not too bassy or treble-heavy – where it’s at its sweetest and you can hear every note clearly. This is where you want your microphone to be.

After a few recording sessions, you’re likely to notice the ‘low-end build-up’ you tend to get right next to the soundhole, and the ‘high-end build-up’ that happens when you place a microphone somewhere near the 12th fret. Where you place the microphone depends on your recording setup and the microphone you’re using, which will all help to shape the sound of the recording. However, that ‘sweet spot’ that you’re searching for always lies somewhere between the soundhole and the 12th fret.

Avoid Dynamic Microphones

Before you even think about recording, you need to figure out what kind of microphone to use. You could have the most stunning-sounding guitar in the world, but if you don’t have the right microphone or even if you set up the right microphone incorrectly, you’re not going to get a good recording. To record any acoustic instrument in the best quality possible, you’re likely to need a condenser microphone, and definitely not a dynamic microphone. The reason is obvious. Condenser microphones are far more sensitive and respond to peaks more swiftly. A condenser microphone picks all of these details up far more precisely than a dynamic microphone can – unless you have a really high quality dynamic microphone. Dynamic microphones, like the Shure SM57, for example, are really good for miking-up guitar amplifiers that don’t need such a high transient response. Besides these two types of microphone, there are also ribbon microphones that, more or less, offer the same kind of response as a dynamic microphone but are able to register extremely low frequencies – as low as 30Hz. The problem with ribbon microphones is that they’re pretty vulnerable bits of kit. While you can comfortably throw around a condenser or dynamic microphone on stage, a ribbon microphone just wouldn’t be able to handle it. However, ribbons have made a bit of a come-back in recent years because they have such a nice and soft, warm character to them, and they tend not to sound as shrill as some condenser microphones can, making them a pretty good alternative. They’re also more flexible, since ribbon microphones are generally used for recording woodwind and brass instruments and electric or acoustic guitars, so if you want to make distinctly warm home recordings, then they’re actually a pretty decent choice. Just bear in mind that, like condenser microphones, active ribbon microphones will need to be fed phantom power in order to function (note: never feed a passive ribbon microphone phantom power).

There are two different types of condenser microphones: small-diaphragm and large-diaphragm. The difference between the two is that large-diaphragm microphones capture slightly less detail than their small-diaphragm counterparts, the flip side being that they do sound a bit fuller. The sound of small-diaphragm condenser microphones is the most true-to-life, which makes sense as every last detail is captured and the frequency response of these microphones is extremely flat. A large-diaphragm condenser microphone is your best bet when you’ve got an acoustic guitar at the core of your composition, which is usually the case with singer-songwriters. Need to record a crowded arrangement where the acoustic guitar plays a relatively small role? Then go with a small-diaphragm mic instead. Read our blog on the Difference Between Dynamic & Condenser Microphones for an even deeper insight.

» Large-Diaphragm Condenser Microphones
» Small-Diaphragm Condenser Microphones
» Ribbon Microphones

The Recording Space

The space you use to record in has a pretty big role to play in the quality of your recordings. Generally, you should avoid recording in a room that’s too small. The problem with small recording spaces is that they often cause resonance problems, since the frequency of ‘echoes’ tends to match the mid-range frequencies of a guitar, making it really difficult to find the right microphone position. Every little change in the position of the microphone or guitar makes a big difference when it comes to the frequencies that the microphone finally picks up. If your recording space is big enough, life immediately gets much easier, but of course, if the room is too big, it also comes with its own issues. When the space is too big or the sound is bouncing off the walls, it can sound like you’re sitting in a cave, and your mixes will already sound like they’ve been drenched in too much reverb. Even any objects in the room will have an effect. Of course, if you’re recording, you might want the natural reverb and ambience of a larger space, but if it’s not what you’re after, then some acoustic treatment might be needed. Even just installing a single acoustic screen in the right place can improve recording, but when it comes to acoustic treatment, there is a balance to be struck, because if you have too much, the effect can be just as negative as having none. So to record your acoustic guitar, it’s worth finding a good space that has some nice natural reverb to it and lends a naturally ‘full’ sound to the guitar. If you’re a guitarist yourself, then you’ll be able to hear what’s best. If you’re not sure, you can always walk around the room while strumming a few chords to find the sweet spot.

The Single Mic Technique

You can use a number of different techniques to record an acoustic guitar. In recording studios, a special setup involving two different microphones that can be placed in various different configurations is often used. Usually, sound engineers will have their own preference when it comes to the gear and kind of space that they use, and these preferences are specifically formed by their experience in the recording game. If you’re recording at home, the easiest and most flexible way to record and get the best results is to use either the single mic technique (also known as the mono mic technique); the dual mic technique (or stereo technique); or if you have an electro-acoustic guitar, you could combine a single microphone with the pickup. The technique you decide to use will ultimately depend on what’s possible and the gear you have access to. With the single mic technique, of course, you’ll just need a single microphone and can start by placing it around 40cm away from the 12th fret, between the 12th fret and the soundhole. In any case, always play around and experiment with the distance, since every microphone will give you different results. If the setup isn’t giving you the sound that you want, then try placing the mic a little closer to get more volume and detail, and pull the mic back a touch if the sound is starting to distort. Is the sound a bit too dark or are you getting too much bass? Then point the microphone further towards the headstock of the guitar. If the sound is a little too sharp, then point the microphone more towards the soundhole. An alternative setup if the sound is too sharp is to place the microphone near the bridge and point it to the right of the body of the guitar. It’s also worth noting that, when using the single mic technique, the sound can be a little lifeless, monotone and, for want of a better word, boring. But if you’re recording something that’s going to be mixed in with other instruments, then this more flat sound won’t be such a bad thing. And, if you’re recording a full band, then using the single mic technique to record the acoustic guitar is actually a preference. But if your acoustic guitar is going to form a focus point in the finished track, then it’s a better idea to use a different setup, like the dual mic technique. Also, if you had a more sparkling sound in mind, then try doubling the guitar – so record the same part twice; once with the microphone placed closer to the soundhole, and once with the mic placed nearer to the headstock. With both takes, you can set up the microphone at the same height of the 12th fret, or you could use the same setup that will be described in the stereo mic technique below (where one microphone is placed at bridge height, and the other is placed at the height of the 12th fret). The one condition of using this two-take technique is that you have to be able to play the guitar part identically, but once you have them down, you can balance the two takes in the mix, giving the guitar sound some lush sparkle and body.

The Dual Mic Technique

The chance of making a really good recording gets way bigger if you’re able to use two microphones. Known as the stereo technique, the dual mic method gives you more control over the sound when both recording and mixing. To start, place a microphone at the same height as the 12th fret and at a distance of 40cm to 80cm from the 12th fret, making sure it’s pointing to the left of the soundhole. Then, place the second microphone at the height of the bridge and just to the right of the soundhole. An alternative setup is to point the first microphone at the 12th fret, and then point the second microphone at the 8th fret. Play around with the setup, distance and where the mics are pointed to find what works, but what you’ll immediately notice is that, because you’ve set up two microphones, the sound is clearly improved. The more open and natural sound that you get with two mics is easily explained: you have two ears, not one, so when recording with two microphones, the result immediately makes more sense to our brains. There are also many different configurations you can use when setting up two microphones. For example, if you’re using both a small and large diaphragm microphone, you can place the small-diaphragm mic above the large-diaphragm mic, making sure that they’re not touching each other, and point the small-diaphragm mic at the soundhole. The small-diaphragm will then register a sharper sound while the large-diaphragm will pick up a fuller sound. During the mix-down, both recordings can be balanced until you get what you want from them. If you don’t have much time and even less space, then an XY configuration is an option, where you use two microphones placed at a 90-degree angle from each other, while making sure they’re not touching. The angle is then pointed at the sound source, which in this case, is the soundhole of the guitar.

Using a Pickup

If you don’t have the budget for two good microphones, but you already have an electro-acoustic guitar, then you could also experiment with recording with one microphone and the pickup built into your guitar, but bear in mind that you’ll most likely bump into phase issues. That’s because the sound of your guitar will reach the pickup before the soundwaves make it to your microphone, which can result in a strangely hollow sound when you play both recordings at the same time. To solve this problem, you’ll need to use your recording software to zoom in on the two tracks and literally mirror the microphone recording with the pickup recording. If the audio signals are the exact opposite, the issue can also be fixed by inverting the polarity of one of the takes. Also, the recording quality will heavily depend on the quality of the pickup, and in many cases, the result won’t match up to the kind of sound that you can achieve in the studio. But, if you don’t have a microphone, then a good quality pickup can still conjure good sound.

A Few Tips

The Best Microphones for the Acoustic Guitar

There are so many microphones available that it seems like an impossible task to figure out which ones are best. On top of that, picking out a microphone heavily depends on your budget and preference. The Rode NT1-A large-diaphragm condenser microphone is definitely a ‘safe bet’, especially since, according to those in the know, you’re getting a great microphone for less than two-hundred quid. A step down on the budget-ladder is the Audio-Technica AT2020 small-diaphragm condenser microphone which comes in at around £100, and if your budget is a bit smaller, then there’s the Behringer B-1 – definitely great value for money on that one. These days, there are also plenty of microphones you could get for around £40 up, but I have to say that it does pay to raise the bar a little higher. By paying even a little extra, you’ll get a mic that delivers less noise, has a better build quality and definitely better sound. For those who have the cash to make a bigger investment, then there’s the Shure SM81 small-diaphragm condenser microphone for £350 to £400; the Rode NT2A large-diaphragm condenser (Multi-Pattern) microphone, Shure KSM141 SL small-diaphragm mic, and the AKG C214 Cardioid large-diaphragm mic, all for around £400 to £450; the Neumann TLM 102 large-diaphragm condenser for £700 to £750; the Shure KSM44 large-diaphragm condenser for £1000 to £1050; and the Royer R-121 Studio Ribbon microphone for about £1300 to £1350. Ultimately, any decision you make when it comes to gear will come down to what you prefer. For any singer-songwriters or duos, a model that really floats to the top (if you have the cash) is the Ear Trumpet Labs Evelyn condenser stereo microphone which will set you back about £1900. But if you’re planning to record a lot, then investing in one of these microphones is actually far more likely to give you the results you want than a really expensive guitar ever could.

Polar Patterns

Depending on the microphone you choose – dynamic, condenser (large or small diaphragm) or ribbon – the resulting sound will also depend on the polar pattern. The polar pattern describes the area around a microphone where it’s most sensitive to incoming sound and matters a lot when it comes to the acoustics of the room and how much of it you’re going to hear back in the recording. The polar pattern also matters for the balance of the sound as highly focussed microphones will boost the lower frequencies with more strength the closer they’re set up to the sound source. This is known as the proximity effect, and it’s actually something that omnidirectional microphones aren’t affected by. Besides omnidirectional microphones (which are sensitive to sound coming from all around), there are microphones that have a cardioid (sensitive to sound coming from the front) and microphones that have a bidirectional, or figure-of-8 polar pattern (sensitive to sound coming from the front and rear, ‘deaf’ to sound coming from the sides). For more on pickup patterns, see our blog, Polar Patterns Explained.

At Least Two People

Of course, there’s nothing stopping you from recording your guitar yourself, but it’s going to be much easier, faster, and more efficient with the help of at least one other person since you won’t have to get up every time your recording gear needs your attention, or faff with placing your microphones with a guitar in the way. No matter how independent a singer-songwriter you might be, that extra pair of hands will be invaluable.