From the acoustics of the room to the instrument and player, from the the microphones you choose to where you place them, a lot goes into a quality recording of an acoustic guitar
From The Recording Guitarist © 2010 by Jon Chappell. Published by Hal Leonard Books, an imprint of Hal Leonard Publishing. Reprinted with permission.
When recording acoustic guitar, you can obtain great results with either dynamic or condenser mics, used singly, in a blend, or in stereo. For acoustic guitars, generally what you hear is what you get. If you use a better mic, you’ll get a better sound simply because the mic is providing a more accurate picture of what’s there. And while it’s true that some mic characteristics are preferable to others for capturing acoustic guitar, the better the guitar sound, the less those factors play into the equation.
You can get good results with either condensers or dynamics, but condensers are preferred as they are better able to pick up transients, or the high-frequency artifacts (noise) of the plucked string. A quality dynamic mic like a Sennheiser 421 works very well, though, positioned 18–24 inches away and pointed at the bridge, slightly off axis – as if the “beam” emanating from the top of the pickup were pointed at the 12th fret, and not perpendicular to the guitar’s top. Good miking technique involves nothing more than a lot of trial and error with placement, and then exercising good judgment when you listen to your placements over the monitors.
You’ll often hear people talk about an acoustic guitar’s “sweet spot” – a narrowly defined area where the guitar sounds best. This can be found by plugging one ear and using the other as the mic, pointing it at the guitar while someone plays it and moving around until you find where it sounds good. In this way, you are behaving like a directional mic. Move from fretboard to bridge, upper bout to lower, and vary your distance and angle to the guitar. Your ear doesn’t have the exact “pickup pattern” a mic does, but this can give you a good idea of which area gives you more of the tone you’re looking for.
When recording guitar, you should also listen for the quality of the room sound: make sure it has an ambience that makes the guitar sound good. You don’t necessarily need to understand acoustical theory to know when a room is working for you or against you. If things are sounding good in the room, use a mic to capture that quality. If there are harsh echoes and rattling, take steps to cut the room out of the picture.
Many acoustic guitars, both steel-string and nylon, come with built-in electronics that allow you to plug one end of a normal electric guitar cable into the endpin jack and the other into a guitar amplifier, mixing board, or effects processor. If there are onboard electronics (which include a preamp and EQ), they’re usually found inside the guitar body, with tone and volume controls on the top side of the upper bout.
Pickups are used more and more in live situations, even by the best acoustic guitarists, because of their convenience and manageability. Even in a recording situation, where logistics are not as much of a factor, some engineers and guitarists like the tonal quality of a pickup, and will blend it in with the pure mic sound. One reason for this is because pickups can deliver a more focused bass response than a microphone, and often people will use the pickup of an acoustic guitar to boost its low end while the mic captures the mid and upper frequencies. And of course you can always record just the straight pickup sound (no mic) of the guitar. It’s still unmistakably an acoustic guitar, but it sounds very different from a guitar recorded with just a mic. The sound is described as somewhat “compressed,” “focused,” or “sustained,” and is good for lead lines that need to cut through a busy or noisy mix. There are two types of pickups for acoustic guitars: magnetic and piezo.
Magnetic. A magnetic pickup is most similar to an electric guitar pickup (though it’s optimized for acoustic guitar) in that it uses a coil of wire wrapped around a magnet to capture the vibrating steel strings above it. Since this pickup type is based on magnetic energy, it won’t work on nylon strings. It typically sits in the acoustic’s sound hole.
Piezo. A piezo (pronounced PYE-zoh or pee-AY-tzo) pickup is a thin membrane that’s placed between the saddle (the bone- or ivory-like strip that sits in a slot in the bridge) and the bottom of the bridge. It works not magnetically, but through the varying pressure caused by the vibrating string bearing down on it from above. Contact pickups that adhere to the soundboard are also piezo-based, and some systems have multiple contacts at different points on the soundboard, which are then blended together. Because of recent advancements in piezo technology, the membranes have gotten more sensitive and responsive, and are generally preferred over magnetic pickups for a truer acoustic sound. There are notable holdouts for magnetic pickups, though, including Leo Kottke. And of course, you can always choose one or the other based on the sound you’re looking for or a certain situation.
Combining Pickups with Mics
A potentially negative phenomenon to watch for when playing pickup-equipped acoustic guitars is finger noise. This is the unavoidable skritch the left-hand fingers make when fretting, releasing, and moving along the strings. While this is a natural and listener-tolerated result of playing the guitar, recording guitarists usually try very hard to keep finger noise to a minimum. A pickup tends to give undue prominence to finger noise, because it picks the sound up directly from the string itself, rather than from a distance, as a mic does. Since the mic is some distance away, the musical information (the vibrating string) is usually much louder than the string noise, which is placed in the background. But the pickup tends to give the string noise a bit more “presence,” as though it’s closer to your ear than normal.
One trick that works particularly well in a rock context is to plug an acoustic through a combo amp’s speaker to get an even more compressed, focused sound, and then mic the speaker. You shouldn’t plug straight into the amp’s input, though. A better way is to go into a dedicated mic preamp or even the preamp of your mixer channel’s input. This provides a better match for the two impedances—the output impedance of the piezo and the input impedance of the mic pre. Then, via an aux send, take the acoustic guitar’s signal out of the mixer and run it into the effects return jack of the combo amp, bypassing the preamp stage (because your signal is already preamped). You then have a properly preamped piezo signal run through a nice tube power amp and a midrange-oriented speaker.
This method works well if you’re already in the studio playing an electric through a combo amp and the producer asks you to switch to a direct acoustic sound (and he doesn’t want a miked guitar, as setting up a mic and isolating it isn’t practical). You can have both instruments plugged in simultaneously, and without repatching, switch between the two guitars. Just remember to pull down the fader on the acoustic when you switch to the electric, so that no noise enters through the amp’s effects return jack. This method of using different amp jacks for electric and acoustic guitar works even if you’re not recording via the speaker, but using the slave or Speaker Out of the amp and continuing on to a load box and beyond.
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11 thoughts on “Recording acoustic guitar”
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Operating a studio that’s dedicated to singer-songwriters, I’ve recorded a LOT of acoustic guitars. First rule – listen to the instrument: stick your head down there near the soundhole and listen with both ears. Second rule – stay out of the way of the air column coming out of the sound hole. Mic off-centre and away from the hole. Here’s how we do it: I use a stereo pair of small cap condensors in the RTIF 115 degree pattern. I position them in front of the hole, about 8 inches out. Then I take a large cap condensor and place it near the lower bout of the bass end of the guitar – the part closest to the floor – aim it at the top. Then I take another small cap condensor and place it over the finger board. And finally we put a wide-pattern, almost omni large-cap about 5 feet back from the guitar for ambiance. We run all five of the guitar tracks through Focusrite preamps and check like crazy for phase issues. When we mix, the stereo pair is the main source, with the bass and fingerboard mics for bass and treble emphasis. The ambiant mic drives the reverb. If you can manage five tracks for one instrument, it’s a great sound.
10-4 from rainy BC,
For Recording Acoustic Guitar II go with a simplle approach. First I use an 11 gauge Nano web Elixir string set or other coated string on a Taylor GC8 or a smaller Parlor size or Grand Auditorium size body like a 214CE. I mic the instrument using a condenser MXL V67 by itself. Then go back with a little compression either digitaly in Logic or adding an analog MaxCom dual stereo compressor, then some Reverb or alittle lexicon mpx500 and an EQ or maybe two depending on where I’m at. I also may use adirect box. This way you get some strumming captured and also some hand effects sliding up and down the neck. I place it offset alittle from the center hole in the body. The rest of the processing gets handled when mastering. This works great. I also found that bouncing to -2DB helps before I master to get some headroom for mastering. My album : Personal Mastery can be heard or purchased at http://www.digstation.com search artist SIMES or http://www.cdbaby.com
I like using a Shure KSM32 in the vicinity of the sound hole, abou 8 to 10 inches away. Then I like to place a Shure SM57 up around the nut of the neck because I do like to pick up the realistic raw sound of the fingers moving along the strings with a little fret noise. And finally I like plugging the guitar direct by using its pickup.
All three of these signals are sent through individual channels. This gives me the freedom to to pan each track as I hear it should along with te volume that each signal will be producing. Most likely I’ll leave the KSM32 set in the middle with little to no effect on it. Then I can take the SM57 and pan a little left or right and do the same with the direct signal.
Then as I hear fit I will add a little depth with a touch of reverb or maybe a slight delay. This tends to give the acoustic a big rich sound, but still subtle at the same time. Once the EQ is set correctly you can place it where you want to within your mix depending on the style of song your recording.
I’ve had good results with the M-S or mid/side technique. I use a large diaphram mic like the U-87 and a condenser C-451. Placing the U-87 about 8-12 inches in front of the sound hole in the omni pattern with the mic “sideways” to the hole. You will create a phantom stereo image by using 2 tracks with the same mic input panning L/R and switching the polarity on the R track. I then take the C-451 and place that directly on top of the U-87 on its own track panned center. This gives a great open and airy sound to the acoustic guitar.
Well Jon, you kind of got close there, you did say to listen to the guitar, which most people who write books fail to say. But, listen to it with one ear plugged? Cool ! That’s how I always listen to music, yup. Look, there is such a thing as stereo miking, just put two mics where it sounds good to you, both of them pointed in the direction you’re looking, about the distance apart of your ears. Another really dynamic miking position is two condensers, one above, and one below the sound hole, both pointed at the sound hole about 8 inches out. This let’s you hear the relative motion of the hand, and differentiates the higher and lower strings into a left and right stereo. And most of all, a good large diaphraghm mic directly over the sound hole, at about the same distance as the upper and lower mics, captures the heart of the guitar. Personally, the last sound I want to hear is a mic over the neck, where there’s nothing but finger noise and rigid, thin, unsavory harmonic backwash.
And now kids, a final tip for using acoustic guitar pickups – if you put 2 pickups in the soundhole, one at each end of the hole, you will be amazed to hear that they don’t both hear the same thing, instead, they somehow ‘find’ different parts of the note’s character to illuminate. If you think about it, almost every electric guitar has 2 or more pickups, but for some reason, nobody has ever figured out that the same principles for pickups are true on acoustic guitars. Once you hear what 2 sound hole pickups sound like, you’l wonder why nobody has ever figured out that it sounds great, and has never written a book telling somebody else to do it.
In the end, kids, don’t listen to anybody about how to mic things, because the people who are telling you how to do stuff are the people who figured it out for themselves, and enjoyed and learned from the process of discovery, and then decided there was more money in selling books. Anybody who puts a mic where a writer tells them to put it is either too dumb or too lazy to figure it out for themselves, – discovery is the essence of art.
Why does this guy act like there aren’t mulitple approaches to miking, and why an article can’t possibly give a good suggestion that might cause someone to try something good they otherwise might not have tried? For example, everyone uses condenser mics to record acoustic guitar. I haven’t tried the Senn 421 yet, but after reading this article I’m going to give it a try. It’s not a waste of time to pick up pointers and see how they work for you.