In this blog post I’ll explain several stereo techniques often used to record classical guitar – AB, ORTF, XY and MS (Mid-Side). You’ll be able to hear the difference for yourself and vote for whatever sound(s) you prefer!
The microphones used for this experiment were my Oktavas Mk-012 modded by Michael Joly with cardioid and omni capsules.
The composition on this track is Manuel Maria Ponce‘s Sonata III – 2nd movement, played by me several times over on my Bernd Holzgruber guitar.
The AB Stereo Technique uses two spaced microphones to record audio signals. Recommended spacing between the two microphones is between 40 – 60 cm and the microphones can either be pointed forward or angled slightly outwards. In this experiment I used a combination of all these settings.
1st Sample – AB Stereo, cardioid capsules, microphone spacing [s] 40 cm, pointed forward, distance between the guitar and either microphone [d] 80 cm, height [h] (distance between the floor and the mics) 115 cm.
2nd Sample – AB Stereo, omni capsules, pointed forward, [s] 40 cm, [d] 80 cm, [h] 115 cm.
3rd Sample – AB Stereo, cardioid, pointed slightly outwards, [s] 45 cm, [d] 65 cm, [h] 107 cm.
4thSample – AB Stereo, omni, pointed slightly outwards, [s] 45 cm, [d] 65 cm, [h] 107 cm.
5th Sample – AB Stereo, cardioid, pointed slightly outwards, [s] 60 cm, [d] 65 cm, [h] 115 cm.
6th Sample – AB Stereo, omni, pointed slightly outwards, [s] 60 cm, [d] 65 cm, [h] 115 cm.
ORTF is a stereo technique that uses two microphones spaced 17 cm (spacing between the diaphragms) and angled 110º creating the stereo image.
7th Sample – ORTF, cardioid, [d] 70 cm, [h] 115 cm.
8th Sample – ORTF, omni, [d] 70 cm, [h] 115 cm.
XY Stereo Technique uses two cardioid microphones in the same point, angled typically 90º. This is achieved by placing one microphone on top of the other with the diaphragms vertically aligned (see the photo below).
9th Sample – XY Stereo, cardioid, [d] 70 cm, [h] 110 cm.
MS (Mid-Side) is a special technique using one cardioid or omni microphone (Mid) and one bi-directional [Figure 8] microphone (Side) in the same point and angled 90º creating a stereo image through the MS-matrix.
This means the signals of both microphones should be rearranged separately with the MS-matrix that can be understood by these simple calculations:
Left channel = M + S
Right channel = M – S
This can be done with an MS decoder or a Direction Mixer plugin (for those using Logic Studio). Alternatively, you can do this manually by leaving the Mid channel in the centre and copying the Side channel, panning one copy hard left and the other hard right, reversing the phase of the latter.
10th Sample – MS Stereo, cardioid, [d] 75 cm, [h] 108 cm.
11th Sample – MS Stereo, omni, [d] 75 cm, [h] 108 cm.
So, the sound of which microphone technique did you prefer? Any comments will be highly appreciated!