How Do You Process an Acoustic Guitar?
The acoustic guitar is one of the most popular instruments in the music industry. It’s been on numerous recordings and remains a favorite tool among composers. Despite its popularity, mixing acoustic guitar may be challenging for a novice engineer.
Few instruments are as widely used as the acoustic guitar. Acoustic guitars are present in every genre of modern popular music, from folk to hard rock. While sample-based ‘virtual’ acoustic guitar instruments have improved dramatically in recent years, even a half-decent guitarist will likely give a more realistic performance by playing the part.
The difficulty of reproducing the sound of an acoustic guitar differs from those of an electric guitar. The goal of recording electric guitars is to capture superb tone from your amplifier. With acoustic guitars, the emphasis is shifted more directly to the instrument itself, opening up a new realm of concerns for the final recording.
If you have an acoustic guitar with an integrated pick-up system, such as a piezo, it might be tempting to connect it to your audio interface and play simply. While pick-up devices assist in decreasing the possibility of feedback on stage, keep in mind that every element of the instrument produces a different sound. As a result, a pick-up system will only record a tiny portion of the larger image; only a microphone can capture the complete diversity of an acoustic instrument and the space in which it is placed.
In this tutorial, we’ll explain to you how to get the finest sound out of your instrument and offer some mixing advice within the context of your recordings.
How Do You Process an Acoustic Guitar? | Choosing the Best Space
Before you begin putting microphones, keep in mind that the shape and sound of the space can affect your recording, so picking the proper position is critical. Acoustics is a science in and of itself, but a good rule of thumb to keep in mind is that space with a lot of hard surfaces (such as a bathroom or church) will have a lot of reflections, giving you a more expansive and characterful sound that may be amazing but can also be difficult to manage. However, recording in a room with a lot of furniture (such as a bedroom) will result in a tighter-sounding recording since the furniture absorbs the sound produced by the guitar.
Because your ears are the most useful tool, you have here, a smart place to start is just listening to the guitarist perform in your selected room, identifying the best sounding position, and setting up your guitar and mics there.
How Do You Process an Acoustic Guitar? | Selecting Microphones
Before you begin, you must decide which mics you will utilize. If you’re unsure about the distinctions between these types of mics, be sure to read our blog post about it here. Because acoustic guitars are fragile instruments with a lot of high-frequency information, a combination of condenser microphones is the most popular choice. However, there are no rules regarding which microphones should be used, and experimentation is essential to being an engineer.
With the guitar in great shape, we can start thinking about mics. As a general rule, a dynamic microphone will rarely do the acoustic guitar justice. Acoustic guitars are naturally rich in high frequencies, therefore, using a decent quality condenser microphone will likely produce a more pleasing outcome.
How Do You Process an Acoustic Guitar? | Microphone Placement
Knowing some of the instrument’s foundations will allow you to make educated judgments about where to put your microphone(s). Low frequencies, for example, are highest at the soundhole itself. As a result, capturing the sound here makes little sense if you want a balanced-sounding outcome.
Place the Microphone at the Bridge
The bridge of an acoustic guitar produces the most balanced tone. According to how the guitarist performs, the microphone may get in the way of their arm. Consider positioning the mike just below the bridge and inclined upwards in this scenario. Alternatively, raise the mic above the bridge near the guitarist’s shoulder and point downward. Either way, your microphone should be between 20 and 30 centimeters from the instrument. Moving a cardioid microphone closer will enhance the quantity of bass frequencies picked up. The proximity effect is responsible for this.
Placing the Mic Between the Neck and the Sound Hole
Placing your microphone between the 13th and 19th frets can bring the strings through much more forcefully if you want a louder, more percussive effect. By moving the mic nearer or far away from the soundhole, you may simply adjust the amount of bass response.
Using Two Microphones
It’s worth considering a microphone in both places stated above for the best of all worlds or simply to keep your choices open. When the two mics are mixed at varying levels, a significantly larger spectrum of tones may be obtained. Consider balancing the brighter tones from the neck with the warmer tones from the guitar’s body. A combination of both sounds might work well, depending on musical style and preference.
If you decide to employ two microphones, ensure the signals are in sync. If they are not in sync, this might result in phase issues or comb-filtering. You can reduce potential phase issues by placing each microphone at the same distance from the soundhole. To leave your mic location choices open, it may be preferable to manually modify the time inside your recording program via manual adjustment or by switching the phase on one channel. If your mics sound better in isolation, you may have a phase problem that has to be investigated.
Whatever microphone or approach you use, keep in mind that you’re trying to capture the entire sound of the guitar, the broad image if you will. Placing the mic closer will generally generate a drier sound, while moving it further away will bring more ambient ambiance. If you place the microphone too close to the instrument, you risk producing an artificial tone representing only one aspect of the instrument. Experiment with distance and location while wearing closed-back headphones to see what happens. Getting it perfect at this point might save you hours of trouble later on in the mix.
How Do You Process an Acoustic Guitar? | Mixing Your Acoustic Guitar
The entire tone of an acoustic guitar is mainly decided at this moment in the game. You should now try to adjust the recording to fit within the framework of the overall mix. In this case, less is more; the following are some common examples.
Balance
Begin by routing all of your acoustic guitar microphones to a bus. This enables fast modifications and the use of signal processing without changing the phase relationship of the tracks. Adjust the volume of the acoustic guitar, so it sits at an acceptable level in the mix after mixing each mic to create a balanced tone. A solid rule of thumb is that the acoustic guitar should be louder the sparser the arrangement. The guitar may be nearly loud as the singing in a minimalist arrangement. In a crowded mix, the acoustic guitar will most likely play a supporting role.
Once again, this is a trick for mixing multi-miked acoustic guitars. Always ensure that the signals from each mic are balanced so that they match in loudness. This guarantees that the guitar is centered appropriately and that neither microphone pushes the listener’s ear to one side. You should also ensure that the acoustic guitar is matched with the other elements of the mix. If it’s the main element of the artist’s music, it should be pretty loud. Alternatively, if it isn’t essential to the layout, you can significantly reduce its volume.
EQ
EQ is arguably the most difficult area for new engineers to master when mixing acoustic guitar. This is frequently because they attempt to add frequency content to the instrument before addressing any concerns. Instead, it’s better to start by removing any sections of the acoustic guitar sound that could be interfering with your mix. The most significant is using a high pass filter (HPF) to roll off a good amount of low end. As a starting point, try adjusting your HPF to at least 120Hz – 150Hz. Then, depending on the density of the arrangement, eliminate more. As previously stated, do not do this with the tune soloed.
After you’ve worked on reducing the poor frequency content in your instrument, you can start shaping its sound with EQ. Don’t overdo it with this step. One or two broad EQ strokes with a wide bandwidth will suffice. If you want the guitar to play a more harmonic role, try adding some material in the 500Hz – 800Hz area. If it’s a rhythmic component, though, you may add more of the pick sound by boosting about 4kHz – 8kHz.
Compression
Compression may be a powerful technique for shaping the dynamics of an acoustic guitar recording. However, when utilized incorrectly, it can entirely drain the vitality out of a performance. When dealing with acoustic guitars, I usually employ modest bus compression. Moderate compression can assist in binding the various microphones together and provide more uniform dynamics.
Set a medium attack time (20 – 40ms) with a medium release time to bring out the rhythmic plucking. Set your attack time to very quick and your release time to 20 – 40ms to draw back on the picking and bring out the body of the chords. In both circumstances, a small amount of gain reduction is required to get the desired effect. Begin with 4dB – 6dB of gain reduction and work your way up.
Begin with a slow attack time—typically 10-25 ms—to assist in emphasizing the attack of each transient. For a more realistic sound, use a short release time, often between 50 and 150 ms. I like to use a modest ratio of 2:1 or 4:1, with a gain decrease of 1-3 dB—just enough to compress the tracks when they need it.
If you’re dealing with a particularly brave performance, a faster attack time might assist enhance the sound’s punch. Just be careful—if you set the attack time too quick, you risk compressing the sound of the pick, which might result in unpleasant artifacts.
Delay
A stereo delay may be a terrific technique to add excitement to your acoustic guitar in the mix. However, the effect should be utilized sparingly because too much might make things excessively cluttered.
When employing this effect, the optimum way is to roll out a significant chunk of the high end (above 3kHz) and low end (below 300Hz). This will prevent the delay from becoming too noisy or muddy, allowing it to just cuddle the guitar’s harmonics.
When employed in a deep mix and synchronized with the beat of a song, the listener should not be able to notice the delay. However, it will be evident when the delay is absent. Once again, a small amount goes a big way.
Reverb
The acoustic guitar screams for reverb, especially with a gentler section. Reverb is an excellent tool for giving the guitar a broader spread and pushing it further back in the mix.
Play around with a reverb that has a medium decay time of roughly 1-2 seconds. A pre-delay of roughly 30ms will move it back in the mix while still keeping it fairly forward, while delays of 50ms or more would make it rather distant.
As with delay, rolling the high and low end is a good way to get a pleasant feeling reverb that isn’t too cluttered.
It’s worth noting that the UAD AKG BX 20 is my favorite reverb to use on acoustic guitar. It’s a touch more expensive than other possibilities, but it sounds stunning in this environment.
How Do You Process an Acoustic Guitar? | Conclusion
You’ve undoubtedly learned that there’s a lot to consider while mixing the acoustic guitar for such a simple instrument. Don’t be scared, though; after a few songs, these approaches will become second nature.
The most important lesson from this post should be to constantly consider the acoustic guitar’s function in the mix. This will guide your usage of EQ, compression, reverb, and delay. Checking the phase of microphones and correctly balancing them with busses is also something to think about while mixing.
Finally, employing automation will assist your guitar tone in developing as the music progresses. Follow these tips, and you’ll be able to take your acoustic guitar sound to the next level in no time.
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