Many times it’s surprising the difference an extra mic can make when miking an instrument. A second mic can add depth and ambiance even without resorting to a stereo configuration, which can be perfect for the right track. Here are 3 techniques for using two mics when recording an acoustic guitar, culled from The Ultimate Guitar Tone Handbook that I wrote with my good buddy Rich Tozzoli.
“The use of a second microphone on an acoustic guitar opens up numerous tonal options. Remember, the sound does not come from the soundhole alone; it’s a combination of all the elements of the instrument – its body, neck, strings, and the integration of the overall design.
The two mic option has many alternatives in terms of positioning, where each mic can be placed on a different part of the guitar. Several mics can be also be placed directly next to each other in order to create a wider sound field. You can also separate them where one captures the direct sound of the instrument and another records the room ambience or is placed over the guitarists shoulder.
Although the mics can be grouped onto just a single track, recording the mics on individual tracks provides more options during mixing.
Two Mic Technique #1 – Recording Different Parts of the Guitar
Many excellent recordings have been made by placing a single mic where the soundhole and neck meet, and another on the body (see the Figure 1 on the left). For example, you could place a small diaphragm condenser such as the AKG C451 on the soundhole/neck to capture the brightness of a guitar, while placing a ribbon such as the Royer 121 near the body of the instrument. Or, you could choose to place the ribbon on the soundhole and the condenser on the body – or any combination of mics.
You can also experiment by moving the soundhole mic further up the neck to increase the brightness captured by that mic, or further towards the bridge to darken the tone. When placing a mic on the body, it’s best to listen to the instrument first, as every guitar has it’s own unique projection. Once you’ve listened and found what you think is a sweet spot, place each mic the same distance away from the instrument.
The reason you should try to place both mics at the same distance from the guitar is so that they record in time with each other. Any slight time delay between the mics, even if not noticed during recording, can cause the mics to be slightly out-of-phase with each other, which will cancel out certain frequencies and cause an almost ‘washy’ effect. An easy way to check phase is to listen to one of the channels in and out of phase, either by applying a plug-in (with delay compensation!) that has phase reversal or selecting it on your mixing console or microphone preamp. If you notice one of the mics is out of phase, you can either move the mics or try to visually adjust the waveforms in your DAW.
With the old adage ‘there are no rules’ in mind, the above information should be taken with open ears. Some very cool guitar sounds can be had by actually recording out of phase, or better yet, by sliding separately recorded tracks on your DAW by a few milliseconds. This can create a short delay sound, which in certain productions, may actually work sonically to lift the guitar louder in the mix. A few minutes of experimenting should tell you what works and what doesn’t.
One last thing to think about with recording separate parts of the guitar. If you have one high quality mic and one that’s simply mediocre, it makes sense to put the good mic in the most important position, which is usually the neck/soundhole. By letting the quality mic do the ‘heavy lifting’ of capturing most of the sound, the other mic can then be placed either on the body or the strings to complete the overall sound.
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| Figure 2: Close and ambient miking |
Technique #2 – Close And Ambient Miking
Another technique using more than one microphone involves placing a mic close to the guitar and another in the room to record the ambience (see Figure 2). The first mic, which can be placed either at the usual fretboard/soundhole position or near the body, will capture the more direct sound of the instrument. The second mic should be placed at least three feet further away from the first mic (out in the room) to maintain proper phase integrity.
This method is quite effective when using either a small diaphragm condenser or ribbon mic up close, and a large diaphragm or omni mic as the distant mic. Make sure to achieve a good recording level on the room mic, as the sound level will obviously be less due to the distance from the source. This technique depends upon the quality of the room and the actual amount of room space that’s available.
Two Mic Variation #1
Another optional placement of the second mic in the room is to position it above the shoulder or head of the player, facing towards the front of the guitar. This approximates what the guitarist hears at the playing position and can add a nice sense of depth to an acoustic recording. Try using a shotgun mic, if available, placed above the player’s head or shoulders. By virtue of its design, shotgun microphones are highly directional and will minimize the recording sensitivity to the left, right and rear, focusing on the sound projecting in front of the guitar.”
