Posted by Brian Lindsay on December 10, 2016
As such a versatile instrument, the sound of the acoustic guitar ranges from the rhythmic undulations of reggae to the heartfelt yearnings of a simple ballad. This instrument does not emanate its rich tones and overtones from the soundhole alone. This is a whole-instrument affair. Sound projects from the panels of the body, the strings and even from the resonating fretboard. As we explore the fine skill of recording acoustic guitar, keep this in mind.
We all know that great sound starts at the source, but with all the cool equipment, processors, hypnotizing meters and lights, we may need to be reminded of this from time to time. Always look for that great sound from the source.
Because of the fact that the acoustic guitar can be harder to service and modify than the electric guitar, there are fewer things that a musician or studio engineer can change on an acoustic guitar when it is brought into a recording session. Limited as they may be, there are a few things that may positively affect the sound of an acoustic guitar that you find yourself recording.
Renting an acoustic guitar may be a worthwhile possibility when a client comes in with an instrument that sounds like an angry cat. We are artists and recording engineers, not magicians.
You should NEVER use the direct output alone for the whole of your guitar sound. It’s not that I have anything against the sound of an acoustic guitar output. I just hate that sound in every way. Are we communicating here?
Having said that; It can be beneficial to record the direct output to a separate track. This extra track can be shaved, neutered and used to subtly reinforce the miked sound of the guitar.
Keep in mind that the direct signal will reach the recorder before the miked signal will. If the direct track is to be used constructively, it will need to be slid back (delayed) so that it lines up with the miked signal and does not create comb filtering effects
If you find yourself recording the direct output from the guitar, be sure to run it through a dedicated acoustic guitar preamp before it goes on to your recorder. While the flashy feature of the BBE Acoustimax may be their groovy Sonic Maximizer, I suggest going easy on the Maximizer and using the preamp, EQ, low frequency notch filter and other features that cater to dialing in an acoustic sound to refine the signal before it hits the recorder.
I’m going to open up this can of worms, and I’m not even going to feel bad about it. Aside from some healthy discussion about worthy microphones to try on an acoustic guitar, this subject will bring the couch commandos right out of the woodwork. It’s OK. Just laugh about it and do things your way.
We can all learn something from the fact that the SM81 tends to find itself pointed at plenty of acoustic guitars. Small diaphragm condensers generally have less off axis coloration. I know this is a sweeping generalization, but it’s true. This speaks to the fact that the sound of an acoustic comes from so many places on the guitar. That reduced off axis coloration is an important feature for any mic used on an acoustic, especially as you get closer to the guitar. You will find that the mics considered to be more desirable for acoustic recording will usually exhibit this feature. Watch for it in this list of mics.
Did you really hear what I just said above about off axis coloration? This blight is much reduced in the performance of the SR30 as well. If you take a look at the spec’ sheet of the SR30 or test it with your ears, you will find that the frequency response from the side of this cardioid patterned mic is much better than other mics from the front. While this is a bit embarrassing for some mic manufacturers, this is one area where Earthworks shines brightly. I have recorded some of the most beautiful sounding acoustic guitars of my career with a pair of SR30s. These mics not only shine with their extended high frequency response; they capture rich, coherent lows as well. Pawn a kidney, buy a pair of these mics and prepare to have your breath taken away.
The NT2A offers a bit of versatility in switchable polar patterns, high pass filters and pads. This comes in handy when you try out some of the different mic techniques that I will dish up later in this article. This is a large diaphragm mic, so the off axis coloration spec’ won’t match the previous two small diaphragm mics. This mic finds its way in front of a lot of acoustic guitars for very good reason. Give it a whirl and you will see why.
The way this mic looks a bit like a dragonfly is indeed cute, but there is more to it than interesting looks. Engineers all over the world have begun to praise Blue microphones as having a worthy place in their mic locker. The unique looking, rotating head is actually pretty handy when positioning the diaphragm for the best sound.
Everybody loves a Neumann, right? Although this is a spendy mic, sometimes you have to pony up the coin to get the right tools for the job. With switchable polar patterns, low frequency roll-off and a pad, this mic can be used in a number of guitar miking schemes. Of course, the U87 AI shines in a lot of different recording situations, but we are focused squarely on acoustic guitar at the moment. There are other mics on this list that will handle higher SPL, but with a spec’ of 127 dB, you would need to have a pretty excited guitar player for this to be a problem.
Just in case you don’t want to wait for your turn to win the lottery to stock your mic locker, let’s talk about a worthy but moderately priced large diaphragm mic. The C214 is a dual diaphragm mic that is fixed on a cardioid pickup pattern. The power handling of this mic is an impressive 156 dB. Considering that a jet plane comes in at 140 dB at 50 meters away, I would say that you can put this mic in front of anything in your studio with no worries. You find these frequently being used on acoustic guitars as well as electric guitar amps. It has a bass rolloff switch to help combat the proximity effect if you feel you must put it really close to the guitar.
If the U87 is a bit pricey for you, but the C214 fails to make your eyes water, faint not. There is a worthy option from Neumann that may be just what the engineer ordered. The TLM 102 carries the Neumann reputation with it, but simplifies the design a bit to bring the price down to planet earth. The TLM 102 is fixed on a cardioid pickup pattern and can handle up to 144 dB SPL. There is a slight boost above 6 kHz. This can add some nice presence to an acoustic guitar track.
While I could go on all night about every mic you could stick in front of a guitar, you can get that kind of information overload at the nearest recording forum. Let’s roll up our sleeves and get into some useful ways to use all those mics.
Before rolling through some of the best miking techniques you will find anywhere, I want to point out something that will serve you well if you listen. The ultra-secret technique is this: listen! Before you shove several thousand dollars worth of microphone right in front of the sound hole, listen to the sound of the particular acoustic for a moment. Plug one ear and move your head around the guitar while it is being played. Note the particularly nice sounds and where you find them. Although a mic does not pick up sound the same way that your ear does, it pays to get familiar with each guitar in this way before proceeding. After you have the lay of the land, ignore the strange looks you get from the guitar player and reach for your mic and stand. Try to capture some of those yummy tones that you found while exploring with your ear.
A useful variation of this move is to employ the help of an assistant to move the mic around the various zones of the guitar while you listen from the control room. Even if you do have the help of an assistant, I still suggest that you evaluate the sound of the guitar with your ears first. Really listen to every single acoustic guitar before you record it. The effort will pay off.
If you can not handle capturing the character of a guitar with just one mic, don’t bother moving on to multiple mic techniques. If one good mic is all you possess, know that you can still grab some amazing sounds from an acoustic guitar if you know what to listen for.
Don’t make the mistake of thinking that all the sound is coming out of that hole right under the zone where the guitarist typically strums. Most of the time, if you just stick your mic right up to that hole, you are going to get a boomy sound that will have irritating variations intermixed every time the guitarist’s hand moves between the mic and the sound hole. Seriously, don’t develop a sound hole fixation. That’s just not natural.
If you do find tones in the vicinity of the sound hole that you like, follow a few simple rules to safely put your sound hole fetish to work:
As a great starting point for setting up a single mic on an acoustic guitar, try pointing your mic right at the juncture where the neck meets the body of the guitar. Back the mic up at least 18” and see what that does for your aural sensibilities. Don’t forget to rotate the mic a bit and search for a sweet spot that may be lurking nearby on the guitar.
One worthy purpose of using multiple mics on an acoustic guitar is specialization. This means you use one mic (a large diaphragm condenser) to pick up the full sound of the guitar and then use the other to pick up the nuances of the strings and even the percussiveness of the pick if the song calls for it. Using multiple mics to specialize on the elements of the particular instrument and keeping each signal on its own track will allow you to dial in just the right balance of body and brilliance when it comes time to mix. Those brilliant string sounds are often found by pointing a small diaphragm mic at the upper frets of the neck. When capturing this element to be combined with the body of the guitar, it may be ok to get a bit closer to the guitar than you might do with just one mic. Let your ears be your guide. Always check for comb filtering effects caused by timing (distance) differences between the mics. Adjust the distances or phase switch on one mic to remedy this problem.
For a true stereo image of the acoustic guitar, try XY stereo miking. Keep in mind that a lush sound, both wide and immersive, may only work for songs that are not busy with lots of other instruments. You will also need to be certain that you have the capsules of the two mics aligned perfectly in relation to their distance from the instrument. A small test wherein you change the alignment of the two capsules slightly will convince your ears of just how critical this is. You can cheat on this issue by using an On-Stage Stands BY500 stereo mic bar. These handy bars hold two mics on one mic stand. This will allow you to set the perfect XY alignment and then move the whole concoction around to find the optimal placement of the stereo group. As an alternative to precise alignment of two mics, you may want to consider just using a stereo mic. The Audio Technica 2022 is one such mic. You stick it on your stand and manipulate it like a single mic. Pretty simple, right?
Try a Blumlein pair. Alan Blumlein was an English engineer who had a total of 128 patents to his name. He died in a plane crash during WW2 while testing top secret radar technology. What good does this do us in the studio? Blumlein pioneered a “stereo” mic configuration using two mics set to the figure eight pickup pattern.These mics are arranged one of the top of the other with the capsules as close together as possible. They are also rotated to be at 90 degrees to each other. Aim this conglomeration at your sound source and the result is a nice stereo image from the two channels with a nice helping of room ambience thrown in as well. This technique is only suitable for studio rooms that have good sounding acoustics.
A large diaphragm condenser paired with a small diaphragm condenser makes a great mid-side configuration. The trick here is that you have to be able to switch the large diaphragm condenser to figure eight pattern. Point the two lobes of the figure eight perpendicular to the face of the guitar. The “mid” mic will be placed just above the other mic, with the capsules close together. Aim the small diaphragm condenser straight at the guitar. Once you have these two tracks on your DAW, you will need to duplicate the “side” track and flip its phase. Pan one “side” track left and one right respectively. Leave the “mid” channel panned to the middle. The great thing about this technique is that it is completely mono compatible. When mixing with MS tracks, keep in mind that the more you blend in the “side” tracks, the more of a stereo effect you get.
I saved the vertically spaced pair for last because it is a favorite of mine. It seems to fit into situations where the acoustic guitar is the main instrument in an uncluttered song. Try this on and I know you will like it as well. Use two small diaphragm condensers that have a cardioid pickup pattern. These mics will be placed one over the top of the other vertically with one pointing at the lower three strings and the other pointed at the upper three strings. These may also be set up “crisscrossed” as well. Pan these two tracks left and right and you will get a sense of the guitar being spread out in front of you.
While EQing an acoustic guitar seems necessary most of the time, you should strive to get the tone and character you want right from the source. It’s really difficult to “fix” the sound of an acoustic guitar with EQ and not mess up something else in the process.
Bear in mind that an acoustic guitar that is EQd to fit in a busy song will most likely sound a bit thin if you solo it. Be prepared for artists to comment on this. Unfortunately for most bands, a lot of musicians do not grasp the concept that there are other people in the band besides themselves. This is a fact of life that you, as a studio engineer, will have to cope with.
Every acoustic guitar is different, and you will need to use your ear first when making EQ cuts or boosts. Here are some frequency ranges that are worth your attention when EQing an acoustic guitar track:
The acoustic guitar is a very dynamic instrument. This can be both a blessing and a curse. While I can easily tell you that the acoustic guitar can really benefit from some wisely crafted compression, I will also tell you that it often suffers all kinds of atrocities at the hands of inexperienced engineers.
Have you ever heard the story where a child sneaks a puff of a cigar and gets caught by his parent in the process? As the story goes, the loving parent decides to teach the child a lesson and buys a whole handful of them. He sits the child down and makes him smoke one cigar after the other. This goes on until the child is so sick of smoking these cigars that he cannot stand the smell of them. The child is “cured” of the bad habit and all is well in the world.
While I am not speaking to the intricacies of parenting, this story makes a good point. I want you to do this same thing with a compressor on an acoustic guitar track. Crank it up. Overdo it. Smash the smithereens out of that guitar until you cannot stand the sound of it one second longer. Remember the sound of an over-compressed acoustic guitar and when you hear it creep up in your mixes, run the other way screaming.
As a general rule: Less instruments in a song equals less compression that you are likely to need on the acoustic track. Aside from using a compressor to subtly tighten up the dynamic range of a guitar recording, we tend to use them to further narrow the dynamics so the quieter parts do not get lost in a busy mix. Let’s take a look at some starter compression settings that may work for an acoustic guitar:
When do you use an optical compressor or a VCA compressor? This is a good question. If you don’t understand what different compressors excel at, your ability to bring them to bear effectively will be reduced significantly.
If you plan on using a chain of compressors, which I sometimes suggest, you are going to need to have a handle on the art of extreme subtlety and also understand what the different compressors do well. Check out this article (scroll down to the subsection “Compression”) to read up on chaining compressors.
Let’s take a look at what the different types of compressors do well.
When thinking of reverbs and other spatial effects for the acoustic guitar, I feel inclined to remind you to first consider whether the particular song has enough space for much reverb on the acoustic guitar. Since there is such a wide sonic range of content in the acoustic guitar, reverbs need to be used judiciously. If you do use reverb, consider limiting its sonic range through the use of a high pass and low pass filter. This will help things to not get out of control in the mix.
If you have to record an acoustic guitar in a completely dead room (picture: the wall of old mattresses), you may really benefit from adding in some barely perceptible room reverb. Simply dial up a medium sized room reverb and turn the mix percentage down until it seems like you cannot hear the reverb any more. Next, bypass the reverb. If you only hear the difference when shutting the reverb off, you are on the right track. This provides some nice dimension without muddying up the mix with walls of reverb.
If you feel the need to set the acoustic in a larger space with the use of reverb, feel free to do so. Be ever vigilant to keep the reverb from getting out of control. Limit the reverberation with EQ or compression. Put on a pair of headphones and listen to the track carefully. Headphones can accentuate reverb. If it seems out of control in the headphones, tone it down.
Keep in mind that you can give the illusion of vast walls of reverb by using volume automation on your reverb track. When the acoustic is by itself, bump the reverb up a bit. When the rest of the instruments come in, tone it down. Splashing a little extra reverb at quieter junctions in the song can create this illusion without drowning your whole mix in walls of reverb.
If you happen to be one of the lucky few that have good studio room acoustics, set up a stereo pair of mics in your lush sounding room and record some ambience tracks in addition to the main guitar track.
I would suggest that you look into convolution reverb. Although it is processor intensive, it can yield some very realistic sounding reverbs. When using a convolution reverb, you first select and load an impulse file. This file was created by sampling the reverb in a particular room or piece of equipment. These unique reverb characteristics of the sample are convoluted with the audio you feed through it and the result is the impression that you recorded the instrument in that nice cathedral or warm wood room.
Here it is. The section of this article where I get to pass on the ultra-useful and sometimes strange bits of information that make life easier in certain situations. I love pocketing tricks of the trade. They are often hard-won and well worth the effort.
Recording the acoustic guitar takes some finesse. You will need to learn how to listen for the many facets of an acoustic instrument’s tone in order to capture them. Hopefully this post has provoked some interesting thought and provided the tools to do this job well. Happy tracking!
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