3 keys for getting quality DIY recordings from acoustic instruments.
Recording acoustic instruments on your own can seem like a daunting task, especially if you have never done it before and you are recording yourself DIY style. To start with you will need some basic equipment of at least one microphone, an audio interface, a pre-amp, and your DAW. Next you need to adapt a three key formula to your recording project: Your knowledge about microphones, microphone placement, and the quality of your signal. When you understand the relationship between these three aspects, you will have the basis to capture what you need from an acoustic instrument even with minimal or inexpensive equipment and in most any environment. The more you research these subjects the better prepared you will be. The formula is a trial and error process of experimenting with different mics in various positions and adjusting your levels until you find the sound you want. This procedure of selecting mics, mic positioning and finding your levels is a craft that should be approached with patience.
Knowledge about microphones
There are many different types of microphones that can be used but an important detail to familiarise yourself with is the microphones polar pattern. The polar pattern is the three dimensional space around the capsule where the mic is most sensitive to sound. This pattern exhibits where microphones receive sound and where they don’t. When you have a good understanding of microphone polar patterns(the three basic are cardioid, bi-directional and omnidirectional) you will have a better idea of which mics to use and how to direct them in a way that reduces undesirable background noise or unwanted reflections. The mic is the tool that not only captures the sound of your instrument but also of your recording space. The polar pattern will serve as a guide when you are finding the best balance between the two.
Every microphone has a diaphragm which is a thin device that is used to capture the vibrations of a sound wave and then that acoustical energy is converted into electrical energy (which is your audio signal). Diaphragms vary in size and depending on its size it will have different characteristics in its sensitivity, frequency range, dynamic range, self noise etc. Typically the large diaphragm mic is more sensitive and has a narrow frequency range whereas the small diaphragm mic has lower sensitivity and a wider frequency range.
The two most popular microphones today are the condenser and the dynamic. The most important difference between the two is that the condenser mic is good for recording any instrument as long as the sound level pressure isn’t too strong (guitars, strings, pianos etc.) and the dynamic mic is better for recording at high sound pressure levels (drums, percussion etc.) but it also can be useful and sound remarkable in low sound pressure recording situations. Each different microphone has a personality that it gives to a recording. For instance, sometimes you want to have an acoustic guitar that will sit comfortably in the middle back of the mix as a rhythmical texture and other times you want an acoustic guitar right up front in the mix as a solo. In the process of recording either of these guitar parts you would try out different mics and different positioning. You don’t want to create the novelty of your instruments sound completely in post-production, try and create it live and it will feel more natural in the mix.
Mic placement involves understanding the various sources of sound coming from your instrument in relation to the environment you are recording in. There are many ways to mic any instrument depending on what you want it to sound like. Here are a few basic examples of mic placement for various acoustic instruments.
Piano: One mic on the low strings and one on the high strings. The further the away from the strings the more space you will capture but also the more expanded the sound wave coming from the piano. You should also experiment with an open and closed piano lid.
Guitar: point a small diaphragm mic at the 12th fret about 20cm away and point one larger diaphragm mic at the bridge about 30cm away. Adjust the mic positions while playing and listening in your headphones until you find what is best for you. Tip: don’t wear a shirt with buttons when recording acoustic guitars, they can click and tap on the guitar while you are recording and you might not notice until listening back after playing your fingers to the bone trying to get the take.
Drums: Place two small-diaphragm condenser mic about two meters above the drum kit, each at a 45 degree angle on an XY stereo mic stand. Adjust the height accordingly. When recording snare with top (dynamic) and bottom (small-diaphragm condenser) be sure to experiment with height and pointing position as well as inverting the phase of your bottom microphone so that the two don’t cancel each other out when played together on your track. For the kick and toms use dynamic drum mics.
The quality of your signal
When musicians were recording to analog they would push the sound hot in order to not hear the hiss and the hum of the equipment. The hotter you pushed it the better it sounded because tape saturation is a natural compression that gives the subtle impression of sounding warm. Now most musicians are recording digital and they still want to get that warm sound but it is not possible by pushing the signal hot to digital because you will only get clipping. If you are recording digital and you clip and you can see it on your DAW, you might as well scrap it because it will sound horrible no matter how much you work at it with automation and plug-ins. You don’t want to record with high gain into your digital system but you can turn it up in your monitors so that it sounds hot in your headphones while performing but still the actual recorded audio signal is in a comfortable sweet spot.
Remember you can always boost a signal in post-production but you can’t really go the other direction without your recording sounding poor. You have to experiment with your levels to find the perfect loudness and at the same time be sure not to record sound that’s too quiet. The key is to push your levels so the VU meter consistently hits 50 percent and 70 percent at peaks. This way you should get a quality signal that will sit well in any mix even if parts of the performance get louder in volume. Be sure your input volume is as low as possible on your interface and to push the sound up with your pre-amp, not the interface, in this way your signal will be solid and your recording will sound dynamic and full.