Stereo Miking Techniques (Part.1)

Regarding the stereo recording techniques, there are different ways to proceed according to the type of microphones used. However, they all are based on the following 2 concepts : Intensity stereo recording or Phase stereo recording.

INTENSITY STEREO RECORDING

The stereo imaging is created by the fact that the level of a given signal differs between the microphones used to record a sound source. One mike being positioned a little bit more towards the “sound source” as compared to the second microphone. The results are that the levels received by the 2 microphones are slightly different.

One advantage of the intensity stereo recording is that it offers (if needed) a good compatibility with “mono” due to the fact that the capsules are stacked. However, the stereo image perception will remain less “natural” than a signal recorded with the Phase stereo recording technique.
One example of an intensity recording technique is the so-called X-Y recording. This technique is sometimes also called coincident.

Ones should recall that due to the lack of differences in time-of-arrival/phase ambiguities, the sonic characteristic of X-Y recordings has less sense of space and depth when compared to recordings employing a “Phase recording setup”.

PHASE STEREO RECORDING TECHNIQUES

Because the microphones are – in this approach- not stacked, the capsules won’t receive the sound waves at the same time. While, the distance can be slightly different, the sound velocity being 340 meters per seconds our brain has the capability to create a realistic stereo space.
Generally speaking, these techniques using the Phase recording include the A-B and the ORTF techniques.

This technique is not recommended if you need mono compatibility.

THE MAINS STEREO COUPLES USED FOR RECORDING

Stereo recording techniques are numerous and could be customized according to the effect desired ; however, the main techniques are :

• XY couple
• ORTF couple
• AB couple
• M/S couple

La plupart des autres étant des variantes des 4 citées au dessus, elles ne seront pas abordées dans cet article.

RECORDING WITH THE XY TECHNIQUE

XY couple technique requires 2 microphones with cardioid characteristics and, in the best of the world, matched paired capsules that will present similar or extremely close frequency responses.
Microphones unmatched separately build and bought could (and often have) some slight difference in the frequency response chart in sensitivity.

Cardioid microphones are optimal when their capsules are directed in axis of the sound source. Their sensitivity and response will be modified when they are off axis. I addition, they are restricted to track what is in front and do not record any sound source on the back as shown below.

Generally, small membranes condenser directional microphones are used (but that’s not a requisite rule…). The 2 microphones (and their capsules) are stacked at the same place, typically pointing at an angle between 90° and 135° to each other according to the sound source recorded and the stereo width desired.
They are generally used to record small ensembles such as strings quartet but also as overheads for drums or acoustic guitars to get some larger space image than mono.

One important point to pay attention to is that – in your DAW - the left positioned microphone will be your “right” channel of your stereo track (since is directed towards the right). The Pan has to be set fully right. An vice and versa for the other one.

Thanks for reading the first part of this serie of articles. In the second part, we’ll discuss other stereo miking techniques and especially the ORFT technique.