Technical backstage: Mid-Side and other stereo techniques

Today I started a little column where I brought into focus technicals stuff.

I’ll write short review about equipment in my studio and some tracking techniques that I use and why.

It’s not a didactic section (when needed I’ll link related pages on manufacturer site) but so as to explain my approach to recording.

I’ll post this column once a week (probabily sunday).


Mid-Side technique

It’s a stereo tracking technique by Alain Blumlein based on a coincident array of two microphone, one directional (typical cardioid) in front of the audio source (orchestral ensemble or musical instrument) and one bidirectional (or eight figure) turned by 90 degrees. DPA microphone about polar patterns.

Signals by Mid (cardioid) and Side (eight figure) using a matrix to achieve Left (M+S) and Right (M-S) channels (stereo signal).

L = Mid + Side and R = Mid- Side

It’s possible switch any stereo signal into a Mid-Side couple with another matrix where Left/Right are summed into Mid (L+R) and subtract into Side (L-R). This is a fine technique used, for example, in mixing and mastering to adjust center component like vocal or electric bass (you have to think on a stereo signal builded with three components: Left/Center/Right) and to broadcast stereo signal on FM modulation, where Mid (L+R) is a mono signal and Side (L-R) is component to rebuild the original L/R signal.

A particulary development of Mid-Side technique is double MS technique to make a surround recording (5.1).  Shoeps on double MS technique – pdf  (very interesting paper)


Why I like it

I like this technique for his nice and wide stereo front, mono compatibility (when stereo signal is collapsed Side dissapear) and fundamental possibility to encoding comeback (to rebuild original Mid-Side signals).

It’s important to highlight the front position of the cardioid microphone (Mid) because it’s the best way to shot center audio source. Unlike ORTF and XY where the microphones are angled and the recording may be less accurate for the off-axys coloration.

Since 1997 I realized M-S technique with several microphone: Rode NT-2 (cardioid) coupled with AKG C414 ULS (eight figure), with two matched AKG C414 TL-II and actually with a Shoeps CMC6/MK4 (cardioid) or MK21 (wide cardioid) to Mid and Shoeps CMC6/MK8 to Side.

Most of my recordings of strings ensemble or choir were made with this technique, sometimes I added close microphones (multimicrophones technique) to capture several instruments.


Other techniques that I use

ORTF technique

acronym of Organisation de Radio et Television Française

Developed by French public television, it’s composed by two matched pair microphones spaced at 17cm each other and angled by 55 degrees. It’s a near coincident technique. DPA microphone about ORTF tecnique.

Less wide than M-S tecnique I like it to record stereo close miking (like acoustic guitar), small vocal ensemble and, generally, when I need to minimize environmental reverberation.

It’s not monocompatible but it still works well.

XY technique

Also this technic has been developed by Alain Blumlein, he used a cardioid (originally eight figure) matched pair microphones angled 90 degrees each other with coincident capsule. It’s a coincident technique. DPA microphone about XY technique.

With a stereo front narrow, XY is the solution for small audio source (like a musical instrument) where it’s important monocompatibility, to attenuate a problematic environmental reverberation and to realize a simple stereo technique.

In this gallery I arrange microphones in ORTF and XY techniques.


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