The Ultimate Guide to Recording Acoustic Guitar

December 9, 2018

Acoustic guitar is an instrument that many people want to incorporate into their songs, but the problem is that capturing a quality recording can prove to be quite challenging if you’re new to recording. I’ve put together a list of tips that will help you achieve the professional quality sound you’re chasing, both on a budget, and with high-end gear.

This guide is split up into different sections that each deal with a particular part of the recording process. By the time you finish reading this guide, you should be more than capable of capturing a professional level recording. The sections of this guide include:


Choosing the Right Guitar

The Importance of Using New Strings

Frequent Guitar Tuning

Acoustic Treatment

Microphone Polar Patterns

Microphone Selection

How to Identify and Correct Phase Issues

Microphone Placement

The Mono Recording Technique

The X-Y Recording Technique

The Spaced Pair Recording Technique

The Wide Spaced Pair Recording Technique

The Mid-Side Recording Technique

The Trident Recording Technique

The 3:1 Rule


Choosing the Right Guitar

You can buy a guitar for a couple hundred dollars, or a couple thousand dollars. Surely, a more expensive guitar is going to sound "better," right? Guitars prices are based on various factors such as the materials a guitar is made of, the manufacturer, and other information that we may never be privy to. Each guitar produces a unique tone, meaning more expensive guitars aren’t always better; just different.


If you’re lucky enough to have access to multiple guitars, you’ll know that choosing the right guitar for your song has nothing to do with price at all. You’re going to reach for the guitar that produces a tone that fits the vibe of your track. Nobody has access to every guitar on the planet, so pick one based on what’s available to you and start recording. If you only have one guitar, that’s fine too; it’s one less decision to make.


I recommend you buy a guitar through Sweetwater if you’re in the market for one. Their sales team is fantastic and can help you find a guitar that meets your needs. Once they suggest a couple of guitars, see if your local guitar shop carries the same models so that you can try them out. Sweetwater rewards customer loyalty very well, which is yet another reason to buy with them.



The Importance of Using New Strings

When strings get old, the sound they produce deadens, and they lose their brightness. This is obviously quite an issue when recording guitar because you don’t get to experience the guitar as it’s intended to be listened to.


You know that black stuff that builds up on your guitar strings? That’s rust and dirt, which indicates it’s time to change your strings. To test for dirt, just run your finger under the strings and take a look at your fingertip. If it’s dirty, it’s time to swap out the strings. Another time you should change your strings is when one breaks. New strings won’t produce the same tone as old ones, so it’s essential that you change all your strings if one breaks.


The benefit of using new strings is that your hands will slide along them easier, and the strings will also stay in tune longer. JustinGuitar suggests buying coated strings, which delay string corrosion, but he mentions that he finds they deaden the sound produced by his guitar more than non-coated strings; choosing one type of string over the other will let you customize the sound produced by your guitar.


You can get a 3-in-1 guitar string winder, cutter, and bridge puller tool to make changing guitar strings easier for about $7 on Amazon.


Frequent Guitar Tuning

Tuning your guitar seems like a given, and although most people will tune their guitar at the beginning of a recording session, they’ll forget to re-tune it throughout the session. In sessions that are unusually long, or in which your guitar is being played a lot, failing to regularly tune your strings can prove to be quite a problem. When you splice one of the recordings from the beginning of your session together with one of the recordings from the end of your session, a guitar that isn’t tuned will stick out like a sore thumb.


I particularly like this guitar tuner from Mugig because it clips onto the end of your guitar, and rotates to allow you to view the screen easily.



Acoustic Treatment

Acoustic treatment is absolutely essential if you’re recording guitar at home. People’s homes are not typically built with acoustics in mind. Most bedrooms are rectangular, space-efficient cells with drywall that are complete acoustic nightmares.


I know “acoustic treatment” sounds scary and expensive, but it doesn’t have to be. You can sound treat an entire room by hanging up moving blankets on the walls for about $60. This isn’t just going to make a slight difference, it’s going to make a big enough difference that you can start capturing professional-quality guitar recordings at home. Moving blankets don’t look very pretty, but if you’re on a budget, they sure beat spending $1,000-2,000 on professional acoustic treatment.


If professionally sound treating your room is something you’re interested in, Auralex has a deal set up through Sweetwater in which they’ll provide you with a free room analysis. You fill out a form, send it to your sales engineer at Sweetwater, they contact Auralex, and then they provide you with suggested acoustic treatment.


Another excellent option for people living in Los Angeles is to contact LA Sound Panels. They come to your studio, conduct a personalized room assessment, and then install the panels for you. Companies like Apogee, Avid, Disney Music Group, and Dolby have used them before.



Microphone Polar Patterns

Each microphone has a unique polar pattern that dictates the physical range which it is capable of recording audio. For example, a microphone with a cardioid polar pattern will record audio in front of the device but reject most of the sound behind it. Other polar patterns include omnidirectional, subcardioid, super cardioid, hyper cardioid, bi-directional (figure-8), and shotgun. Using a microphone with an appropriate polar pattern for the task at hand is important for optimizing audio quality.


Image courtesy of The Podcast Host


Microphone Selection

Condenser microphones are especially adept at recording acoustic guitar. They’re capable of picking up all the smaller details in a sound that many dynamic mics can’t. In general, I would consider condenser microphones to be quite articulate in the way they record audio, making them a perfect choice for recording the nuances of acoustic guitar.


An excellent entry level microphone that can produce a professional sound is the AKG P170. It’s a small-diaphragm, condenser cardioid microphone with a switchable 20dB pre-attenuation pad that can capture sounds between 20Hz-20kHz, and it requires +48V phantom power. These microphones drastically overdeliver considering they cost just $79. This also means that picking up a pair of these microphones for stereo miking applications is within the budget of most home recording enthusiasts.


The workhorse of many professional studios is the AKG C414 XLII large-diaphragm condenser microphone. It has 9 switchable polar patterns, making it an incredibly versatile tool. This microphone provides a slight presence boost to make vocals, and solo instruments like a guitar stand out in the mix. Taking it further, the AKG C414 offers three bass cut filters, three switchable pre-attenuation pads at -6dB, -12dB, -18db, and a clipping LED to indicate overload. This microphone will also require +48V phantom power. With all these features, the AKG C414 will cost you around $1,099, and a matched stereo pair will cost more than double that.


You could also consider renting microphones from a store like Long and McQuade, or Hollywood Sound Systems (if you live in LA). Picking up a pair of high-end microphones for the day typically won't cost more than $40. If you’re doing recording work for a client and they’ve requested a specific microphone that you don’t own, this is a great way to get your hands on it.


How to Identify and Correct Phase Issues

I’m about to talk about “phase issues” a lot throughout this article, so it’s essential that you know what I’m talking about. The waveforms you’re used to seeing in your DAW tell your studio monitors how to behave. They tell the drivers within the speakers when to push and pull the cones in and out of the speaker box. The movement of the cones create waves of compression (high pressure) and rarefaction (low pressure) in the air that travel to your ears. Learn how hearing works for a better understanding of what happens to sound once it reaches your ears.


Phase issues occur when the information sent to your speakers can’t be physically reproduced. If a speaker is told to push and pull by the same amount, at the same time, the result is silence. Yikes! In many situations, full phase cancelation doesn’t occur, but partial phase cancelation does. This can reduce the impact of elements within your mix, causing them to sound weak.


When you sum a mix to mono, you combine the left and right stereo fields. If elements coming from your left speaker are out of phase with elements in your right speaker, phase cancelation can occur. Phase issues can also arise in stereo when the elements coming out of one speaker aren’t phase aligned.


You’ll want to get your hands on a solid phase correlation meter like the one found in iZotope’s free Ozone Imager plugin. There’s a bar with a -1 on one end, and a +1 on the other end. If the moving line is above 0 and spending most of its time towards +1, it means your song is mostly in phase. If it falls below 0 now and then that’s ok, but the closer it is to -1, the more likely it is that you have phase problems.


Ensuring that the audio you record is in phase from the get-go should be a top priority, but sometimes a little editing is required. If you have two audio files that are the same, and that you’re trying to phase align, you’ll want to match up the peaks and troughs in their waveforms. This will ensure that both waveforms are telling the drivers in your speakers to push out and pull in at the same time. Plugins like InPhase by Waves are explicitly designed to assist with this.

Mix Better Now has a great video explaining how you can identify phase issues using your ears and correct them. These techniques are demonstrated using a drum kit, but the same concepts apply to guitar recordings:


Microphone Placement

Finding an appropriate microphone position is actually quite simple. You’ll need a pair of headphones for this process because you’ll be monitoring your input signal through them. First, select the type of microphone placement technique you’d like to use: mono, X-Y, spaced pair, wide spaced pair, or mid-side. The following sections cover these techniques in detail. Once you’ve done this, put your headphones on and move the microphone(s) around your guitarist until you find a position that captures the tone you’re looking for.


There are plenty of articles out there covering specific microphone placements, stating you should be X inches away from your sound source, and I think they work as a decent starting point. However, what really matters is that you have a general sense of what type of character each section of the guitar will generate. This will let you target the part of the guitar that produces the tone you’re after and zone in on a microphone placement that fits the needs of your song.


The four main sections of a guitar that you should concern yourself with while recording are the fingerboard, the area where the body meets the neck (around the 12th fret), the sound hole, and the body of the guitar. Aiming your microphone at the fingerboard is going to pick up a lot of high-end frequencies, and string noise caused by the guitarist's fingers sliding around.


As you aim your microphone towards the 12th fret, you’ll hit what many people refer to as the “sweet spot.” The reason they call it this is that you can often find a nice blend between the brilliance coming from the fingerboard, and warmth emitted from the sound hole and body of the guitar; it’s in the middle of all the action.


The sound hole is rich with low-end frequencies. Pointing your microphone directly at the sound hole can overpower the top end of the guitar, but this knowledge is precious when trying to achieve a balanced sound at a recording level. If what you hear in your headphones is too bright, get closer to the sound hole. If what you hear is too boomy and bass heavy, move further away from the sound hole.


Aiming your microphone at the body of the guitar, below the bridge, captures what I would consider the most muffled of these 4 microphone positions. It leaves out a lot of the sparkle found up the fingerboard, and in some situations, this is what you want.


Don’t forget that you can position your microphone above, below, behind, and to the sides of your guitar. As for how far away from your guitar you should set up your microphone, I recommend starting about one foot away. This will mostly capture the area of the guitar that the microphone is pointed at, and as you move further away, you’ll begin to capture more of the guitar in its entirety.


If you’ve recorded vocals before, you’ll know that when you position your vocalist close to the microphone, the recording ends up sounding very intimate, and rich with low-end. When the vocalist is placed further away from the mic, their voice has more time to interact with the room, and less of the low-end energy from their voice makes it to the microphone. The same concept applies to guitar, but keep in mind that multiple parts of the guitar are producing sound, as opposed to just the mouth of a vocalist.


Something else to consider is the positioning of your guitarist. Are they hugging the guitar too tight? That can affect how the body of the guitar resonates. Try moving them around the room to capture different tones, or put them in an entirely different space altogether. It’s important to do everything within your power to create the sound you’re looking for at a recording level. Some things can’t be fixed once you start mixing your song, so it’s best to address them at the source.


I’ve provided you with many concepts to keep in mind when sculpting your recording. Experiment with moving your microphone around these hotspots, and decide for yourself what sounds best to you. Don’t be afraid to trust your ears.


The only thing you need to worry about if you’re using multiple microphones is phase cancelation. Each of the recording techniques I’ll be mentioning attempt to avoid phase issues, but it’s still best to check for phase problems by analyzing the waveform visually in your DAW, and by making use of a phase correlation meter.


The Mono Recording Technique

Single microphone pointed towards the 12th fret.

Recording with a single microphone is the easiest way to capture a guitar performance because you don’t need to worry about phase issues. All it requires is that you press record once you find a microphone position that you like.


If you only have one microphone, it doesn’t mean that you can’t create a wide stereo recording. Record a second take with the mic in the same position, panning one recording left, and one right. There will undoubtedly be differences between the two performances, but these small nuances can make your wide-panned guitar seem more natural. This recording technique is often used to create thick lead vocals as well.

I’ve included diagrams for each recording technique in this guide, and I should mention that I’ve really simplified them to get my point across. The red dots indicate the microphone diaphragms, and the dotted lines indicate the direction each microphone’s diaphragm is facing.

Justin Colletti of SonicScoop has a great video that covers some different mono mic techniques with acoustic guitar:



The X-Y Recording Technique

Two microphones forming a 90 degree angle, attached to a microphone bar.

If the thought of phase issues keeps you up at night, using an X-Y microphone configuration will allow you to sleep easy. You can set this placement up by first attaching a microphone bar to a microphone stand. A microphone bar will enable you to position two microphones together carefully. Attach your two microphones to the bar and position them in a 90 degree L-shape with the heads almost touching each other. Arranging your microphones in this way will allow you to record a stereo image that captures both the fingerboard and body of the guitar.


If you want to get even more width using this technique, you can angle the microphones further into one another, opening up the L-shape and capturing material both further down the body of the guitar, and higher up its fingerboard.



The Spaced Pair Recording Technique

Two microphones parallel to one another, attached to a microphone bar.

You can use a microphone bar for this technique as well, and just turn your microphones so that they’re parallel to one another. Phase issues now become something to think about, so keep that in mind.


The spaced pair technique is excellent for capturing guitar to be panned just slightly left and right of center. If you have a vocal panned up the center of your stereo image, it will have room to breathe because the guitar won’t be in its way. A good starting position for this microphone technique is to aim the right microphone at the 5th fret, and the left microphone where the neck connects to the body. As mentioned previously, the distance away from the guitar that you position the microphones will depend heavily on the sound you’re trying to achieve.

Rode has a video demonstrating the spaced pair technique in action:




The Wide Spaced Pair Recording Technique

Two microphones equidistant from the sound source.

There’s another version of the spaced pair recording technique known as the wide spaced pair recording technique. When capturing the overheads of a drum kit, this technique is often used with the two microphones equidistant from the center of the snare to minimize phase issues.


For guitar, the setup is quite similar to drums, although the microphones aren’t placed way up in the air. Set up your two microphones a couple feet apart; the farther they are, the wider the sound. Use a microphone cable to measure the distance from the spot you’re targeting on the guitar to each microphone; the distance to each microphone should be the same to minimize phase issues.

Audio Technica has a video demonstrating how to record overheads using a wide spaced pair of microphones. You can apply the same concept to acoustic guitar:



The Mid-Side Recording Technique

A microphone with a cardioid polar pattern aimed at the guitar, and stacked on top of a microphone with a figure-8 polar pattern picking up sound to the sides.

The mid-side recording technique is fascinating because it uses two microphones with different polar patterns, stacked on top of each other, to achieve a wide stereo image that’s perfectly mono compatible. The first microphone uses a cardioid polar pattern, and the second uses a figure-8 polar pattern (indicated by the dashed circles). For example, you could use the previously mentioned AKG P170 for its cardioid polar pattern, and the AKG C414 XLII with its polar pattern switched into figure-8 mode.


Further processing is required to hear the benefits that this mid-side technique provides. With the cardioid mic recording panned to the center, you’re going to duplicate the figure-8 mic recording and pan the duplicate and the original hard left and right. Now, you’ll invert the phase of the duplicate.


This seems like a catastrophe waiting to happen, doesn’t it? The hard panned signals sound super wide in stereo, but they’re going to cancel each other out in mono. Well… that’s the point! The cardioid microphone is panned dead center to ensure that the lost stereo signal is made up for on mono playback systems. Although phase cancelation is often thought of as a bad thing, there are times like this in which you can take advantage of it, and use it to enhance your mix.



The Trident Recording Technique

Three microphones attached to a microphone bar.

The trident recording technique uses three microphones and doesn’t cause the hard panned microphones to phase cancel each other out when summed to mono. To set up this configuration, you’ll start by facing one microphone towards the guitar. Now, place another microphone on each side of the first mic, and point them all in the same direction.


You can arrange the microphones using a four-microphone mounting bar, as it seems microphone bars aren’t typically manufactured for three microphones. Depending on the shape of the microphones you’re using, it may just be easier to use three tripod boom microphone stands.


Same as before, you’ll pan the left, and right microphones hard left and right, but you don’t need to invert the phase of either of them. If you do invert the phase of one, they won’t completely phase cancel each other out, so there’s no point. Instead, make sure that all three microphones are in phase with one another to ensure mono compatibility.



The 3:1 Rule

The second microphone is three times the distance from the first microphone that the first microphone is from the sound source.

The 3:1 rule is more a rule-of-thumb than something that’s set in stone. It states that when recording with two microphones, you’ll often get the best results when you place the second mic three times the distance from the first mic that the first mic is from the source. When written out like this, it seems somewhat confusing, but the image up above should hopefully clarify the 3:1 rule. This setup minimizes phase issues, and you can apply this rule when using a room mic, or when miking multiple guitars at once.


Almost none of the techniques mentioned in this guide use this rule, demonstrating that it’s not essential to capture a quality recording. However, using this rule can help if you’re experimenting with alternative microphone placements.


The following video by Premier Guitar demonstrates many of the recording techniques covered in this guide:



Conclusion

There’s a lot of information in this guide, but to get started recording acoustic guitar, just choose a recording technique that interests you and give the whole recording process your best shot. You can make adjustments to your workflow the more you record, refining your process over time. The most important thing is that you start recording, no matter how much recording gear you have, or the quality of it. You could even use your iPhone’s microphone if that’s all that’s available to you.


I want to invite you to join me in the Black Ghost Audio group on Facebook; it's full of producers currently working in the music industry who are more than happy to help you improve your productions. Leave a comment below if you have any questions regarding this article. Your feedback is always appreciated, and we'll take it into account when we publish future articles!

The guitar PNG used in the microphone technique graphics is courtesy of CI Amper via pngtree.com.

Charles is a Mixing and Mastering Engineer at Black Ghost Audio. After graduating from the University of Manitoba with an English degree, Charles continued his education at Icon Collective, a music production school based out of Los Angeles, CA. He is the founder of Black Ghost Audio, an audio engineering company that creates educational content for music producers. You can send him a work inquiry at www.blackghostaudio.com or contact charles@blackghostaudio.com.