The acoustical guitar

acoustic guitar

I covered some acoustic guitar recording in an earlier post, but only to show how many uses there are for one microphone. I’d now like to revisit the acoustic guitar and share some techniques, advice, and love for an instrument that is the focus of recording for most of you.
If you’re planning on recreating the guitar sound of one of your favourite artists (names clients use to ruin my day include Eric Clapton, Taylor Swift, and Ben Harper), give up now because it won’t happen. Of course, if you tell me you have their exact guitar, physical attributes (down to bone density), exact same technique, and you’re recording with the same gear in the same studio with the same engineers and producer, then shut my mouth. I’m wrong and I admit that I’m wrong. If however, you have 5 years of playing under your belt and a $599 guitar, I’m going to disappoint you. The aim of recording your guitar should be to capture its own unique sound and character, as with your own, in order to record some good music. After all, that’s what it’s all about.

Most of you don’t have the option to purchase a top-end guitar, nor do you have the luxury of hand selecting microphones and preamps to cater to the sound in your head. So let’s simplify things and use what we have. I won’t recommend a Martin D28, I won’t recommend a Royer microphone, and I won’t suggest Neve preamps. I’m merely going to lay out my knowledge and experience of recording acoustic guitars in the hope that you can use it to get the best out of your instrument without needing Clapton’s wallet.

Ready…Wait!
Before you even think about reaching for a mic stand, make sure that your guitar strings are in good condition, that the guitar is in tune, and more importantly, that you feel like playing. If you’re hung over or just don’t feel like playing, it’ll come through on the recording.

Microphones
Take a look at the ‘Weapons check’ post to determine which type of microphone to use to get your desired sound. Generally, a large diaphragm condenser will give you a richer, warmer, fuller sound and a small diaphragm condenser will give you a more detailed, clearer, cleaner sound.

Mic position
This is the big one isn’t it? OK, the first thing to understand is that different type of microphones will produce different sounds, and different parts of the guitar will produce different sounds. A good tip (which has been covered in previous posts) is to wear headphones when placing the mic to give you an idea of the sound you’ll get in that position. Choose a position for the mic and move it around a little, also adjusting the angle of the mic. You will be able to hear subtle differences which will help you to find the sound you’re after.

Position 1
The most widely used mic position for acoustic guitar points the mic at the area where the neck joins the body. This is because you will achieve the best balance between the body and the detail and liveliness of the fretboard. A small amount of time spent with the mic in this neck of the woods should have you finding the sweet spot for your desired sound sooner rather than later.

Position 2
If you find the sound from position 1 a little too thin, or that it doesn’t capture enough of the body, then try the ‘amateurs favourite’ and stick the mic directly in front of the guitar facing the sound hole. I would always use a large diaphragm mic for this position, and you always want to angle the mic slightly so that it is off-axis with the sound hole. Otherwise you will get a boomy sound caused by air coming out of the sound hole directly into the mic (kind of like singing without a pop filter). Again, move the mic around in this general position and listen to the difference it makes. Some producers have the mic a little higher than the sound hole and angled down towards it to emphasise the ‘strumming’ sound.

Position 3
For a bigger, fatter guitar sound, placing the mic around the bridge of the guitar will yield more lower frequency response as this is where the low frequencies of the guitar come from. The issue with this position is that it doesn’t tend to capture enough high frequency to produce a balanced guitar sound, so it may be something to use in conjunction with another microphone placed in position 1 or closer to 12th fret.

Two wrongs don’t make a mic
A common technique is to use two microphones, one on the sound hole and one on the neck, but this usually just gives you two problems to deal with – boom and rattle. The best idea is to get a good sound by using one of these three positions before choosing to use a second mic in another position to complement it. Don’t over complicate things, because you’ll only find problems.

Getting fancy
It’s not always necessary to use anything other than the mic placements listed above, but sometimes out of boredom or just getting carried away, we use more complex mic techniques. 

Mid-side
One of these techniques is mid-side miking. I won’t go over this again as I wrote a post about it not long ago entitled ‘Secret Weapon’. Basically, it gives you a centre-of-the-mix mic placed directly in front of the guitar, and with a little work, another mic picking up hard right and hard left. By bringing these two channels into the mix, you get a huge spread of acoustic guitar right across the stereo field. It can be a very nice sound, but it’s more often just too much guitar in the mix.

X-Y
This technique involves two microphones crossed over in order to get a wider response and more tonality. Mics in this configuration would usually be placed in position 1 with one mic aiming at 12th fret and the other at the sound hole. The good thing about the X-Y technique is that it rarely causes phase cancellation, whilst picking up a good balance of frequency.

Backup
If your acoustic track is going into the mix with several other instruments, you’ll want to be careful about how you record it. A thinner, brighter sound will work much better in a mix than a big, warm, bass heavy sound. If, however, your acoustic track will be the main focus in a mix with minimal instrumentation, or even just voice, you’ll find that you need to fill out the sound more to make the song sound ‘complete’. So, on top of your already sterling guitar sound, you may consider adding a room mic. 
There are situations in which I would add a room mic and there are situations in which I would not. First of all, a room mic really needs to be a large diaphragm condenser, as you’ll want a fuller, warmer sound. Secondly, it really needs to be an acoustically pleasing room. If you’re close miking a guitar, the room doesn’t have to be fantastic as the sound of the room will be very subtle in comparison to the direct signal from the guitar (although with an acoustic instrument, the room does come into it, so it still can’t be a bad sounding room). However, when you set a microphone back from the guitar to capture more ambience, the room suddenly appears, and if it’s a bad sounding room, you’ve got a monster in the mix. I’m not saying that you should have a room like a mini orchestra hall, but you’ll want a moderately large room with nice characteristics and light reverb – even if it means taking over the lounge room for a day. I guess the easiest way to find out is to record a room mic. On playback, you should hear a nice, warm, pleasantly reverberant sound – not a cold, boxy, or overly reverberant sound. Unfortunately, some rooms just don’t work, so you’ll have to make do with some reverb during mixing.

So, a good player with a good guitar in a good room are the raw ingredients to making a good recording. If you sit and play the guitar in the room in which you intend to record and it doesn’t sound great, guess what? It’s not going to sound any better once you’ve recorded it. Actually, it’s almost certainly going to sound worse. 
On the subject of rooms (whether you are using a room mic or not), a small room isn’t great for recording as they tend to have resonance issues and are generally acoustically poor.

With that knowledge, go forth and record your guitars.

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