Performance, recording, calculation, programming by Stefan Kießling, 2023 Website tested with Safari 15 and Chrome 90 on macOS 12.5
Johann Sebastian Bach (1685-1750): Sonate Nr. 4 e-moll, BWV 528: Un poco Allegro. Recorded at Stadtkirche Brandis, Germany. Historic baroque organ built by Christoph Donat in 1705.
The microphone setups MS and XY are close friends. Both provide a stereo image that relies on intensity differences only, which is very precise. Theoratically for any MS-setup there is a XY-setup with the same recording angle and power distribution - and this works also in the other direction: the M signal is the sum X+Y, S is the difference X-Y.
Consequently also the width of a XY stereo recording can be adjusted in post, as it's commonly done with MS. As shown here, a MS setup with two mid microphones gives much more options, especially the power distribution becomes independent from the recording angle (stereo width).
Say we compare the captured power of a stereo setup in its center and at the edge of the recording angle. A MS-setup with Fig.8 and Omni has a constant attenuation of -2 dB of the center compared to the edges, no matter how the recording angle is set in post. MS-setups with directive M-mics show an increasing center emphasis when the recording angle increases. That is the same with XY. By adding an additional Omni for the mid, the center boost can be adjusted in post independently from the recording angle.
It is obvious that the same things works for XY, too: adding a microphone for the mid.
In this sample recording I set up a XY with super cardioids (40°) plus an omni in the middle. Two spaced rooms mics (Fig. 8 ±90°) add some reverb.
You can mix and try out here by yourself. Either by adjusting recording angle, center boost, reverb (the mix will be calculated automatically) or manipulating the faders directly.
Automatic Mixer
Recording angle (reciprocal to stereo width)
No solution.
Emphasize / attenuate center
Reverb
Manual Mixer
The individual tracks where normalized according to the mics' sensitivity, which means, that the mixer behaves, as if all microphones have the same sensitivity and were recorded with the same preamp gain.
Channelstrips 1+2 are summing the XY-mics to the center. This is the M-signal generated out of them.
Channelstrips 3+4 are taking the XY-mics again. However, Y is inverted. This gives the S-signal out of the XY-mics. The output to the right channel is inverted again to achieve the MS-decoding.
Channelstrip 5 is the additional M-microphone (omni in this case).
Channelstrips 6+7 are room mics (spaced Fig. of 8's, angled outwards, like Hamasaki).
With channelstrip 8 you can send the Omni signal to the subwoofer.
For surround sound change the routing of the room mics to Back Left / Back Right. Not all browsers support multichannel output. If you changed the system audio output to a surround-capable audio interface you probably need to reload this page.
Resulting Polarpatterns of the MXY configuration
Mixing those three microphones into a stereo sound that would be achieved with a pair of microphones of the angle and polar pattern shown here.
Show frequency dependent patterns
Stereo image
Shows the distribution of the phantom sources between the loudspeakers and the power distribution. A perfectly straight line indicates, that sounds from all directions are equally captured.