Understanding Audio Signal Flow: Vocals and Acoustic instruments
The third instalment of the series will go over the challenges of recording acoustic instruments and sounds in the physical world. You can find the 1st Part at Understanding Audio Signal Flow: Guitar & Bass and the 2nd Part at Understanding Audio Signal Flow: Keyboards and Synthesizers
Vocalists produce the majority of their sound through the mouth (duh) but there are also complementary sources that are worth mentioning. The mouth opens and out goes a pressure wave exciting the air in a room. But there are also small cavities in our body that are filled with air. They also produce a sound because they resonate much like how an acoustic guitar would resonate a dark hollow tone if you were to speak into its hole. Acoustic instruments work on the fundamental concept of exciting air. It's all fine and dandy until we need to record that into some medium.
The human ear is a device that reads air pressure waves and that's where the concept of the microphone came to be. Microphones sound different per model and brand and are divided into two categories. Before we talk about the differences we need to define the properties. There is frequency response measured in hertz referring to how low or high of a pitch the microphone can interpret. There is also the characteristic of polar pattern.
Polar pattern refers to how focused the microphone is regarding what it picks up in a room.Ranging from the most focused to the least we have shotgun, hypercardioid , super cardioid , cardioid , figure of 8 , and omnidirectional(That's the polar pattern of our ears). The two categories of mics are dynamics and condensers. Dynamics are more suitable for loud instruments and applications where there are suboptimal conditions like live situations. Condenser microphones sport a much more sensitive diaphragm and produce a more detailed result of a sound but are also less focused on what they listen to.
Mic placement and stereo techniques
This section is questionably more important than mic selection and that is because microphones behave differently depending on the distance from the source. As an example dynamic mics ( and condensers to a lesser degree) will produce exaggerated bass response when you get up close with them. This is called proximity effect. So far we have only talked about monophonic capturing of sounds. But humans have a set of ears and we use both sets of information to interpret distance , location , space and timbre. To capture the same sources in a stereo fashion we use stereo mic techniques. Depending on the nature of your source and the desired result you can go for ( among others) an XY, Spaced pair , or Mid-side setup.
The mic pre-amp
You're going into a mixer/dedicated box/audio interface and you hit the mic pre. This will boost the tiny signal that the diaphragm created into line level. It is always recommended to record a healthy signal meaning that you should boost your gain until the loudest point in the recording doesn't clip your input. Of course when you record vocals of a big dynamic range that can be a challenge so a good tool would be a compressor. Don't go ham on it since you want to retain control of most of the dynamic range for the mix stage.
Although we touched on all of the steps the signal travels through we have only scratched the tip of the iceberg. The amount of information you can find online truly resembles the iceberg in that metaphor. My tip would be to go ahead and conduct a recording, after all the most important thing is to get things done, but should you find yourself laying down acoustic guitar parts on a regular basis you should invest in knowledge. Look up the XY stereo technique and add that to your arsenal.
Knowledge is power. Knowing what mic to use depending on the circumstances will save you valuable time and yield better results. A fully fledged studio will be equipped with different mics and mic preamps fit for every job but that doesn't mean your two well placed mics can't stand up to the studio's results.
Price and brand is just that. A week ago i worked with a rap crew on some vocal recordings. They had brought their own expensive microphone to the studio and we commenced recording but after the first couple of takes we realised that their mic did not suit the vocal of the performers. We swapped that mic for a cheap behringer C1 and applied a touch of compression going into ableton. We loved the (in other situations exaggerated) top end of the mic and the body was there. In other words don't let price and brand affect your perception of the result. The only thing that should affect you is...the result.
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