Acoustic Music Production – Part I – Recording in stereo with the mid-side technique

Recording acoustic music seems to be way much easier than recording an entire band. In fact, if we have less instruments to be recorded, the recording process will be easier. The differences between the two patterns will be seen in the mixing process. Last month I entered in the studios to record three acoustic songs. The format of the recording was very simple: two acoustic guitars and voice. For the people that doesn’t understand, if asked, they would say that we just have to put a microphone for the voice and plug the guitars directly on the hardware. However, this can be a mistake.

For recording processes with microphones, there are loads of ways of placing the microphones. Most of the techniques used with microphones are the so called stereo techniques. When we record a signal from a source, the signal will be stored in the computer as a mono signal, which means that, in general, the sense of ambience will be lost, since the signal will be reproduced in both left and right ears with the same characteristics.

Broadly and technically speaking, a stereo signal is a two channel signal. If we want to record an acoustic guitar, for example, in order to avoid the loss of ambience, at least two microphones would be needed. The technique that I used in the recordings of last month was the mid-side technique.

To do this, you need two microphones, one with the figure-of-eight pattern, and another with a cardioid pattern. The microphones are placed very close to each other, in order to avoid phase cancelation. The representation is shown in the figure below:



Figure 01 a) – Mid-Side technique diagram


Figure 01 b) – Mid-Side technique demonstration

Then, after the recording, we will have two signals, each one from each microphone. We then duplicate the signal from the figure-of-eight microphone (by this point you should have three tracks in your DAW software). The duplicated signal will have its phase inverted and panned 100% to the right (or left); the original signal of the figure-of-eight must be panned 100% to the opposite side of the inverted signal (right if the inverted is for left and vice-versa); the signal of the cardioid must be centered in the sound field image. With this, we will have a stereo recording without losing ambience.

In the next part we will talk about mixing acoustic recordings. See you!




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