Question: What stereo microphone techniques can be used with Audio-Technica microphones? (Part 3: Mid-Side)

Answer: Mid-side recording is a stereo recording technique using two microphones, a middle channel (mid) and a side channel. The mid microphone usually has a cardioid pickup angle, while the side is always a figure-of-eight microphone. Mid-side offers the greatest control over the stereo image in post-production. You can control the amount of direct sound from the mid mic and the ambient sound from the side mic, offering exceptional control over the stereo field width. With other stereo recording techniques you are stuck with what was recorded, but with mid-side, ambient space can be adjusted to provide a variable stereo image. Also, the mid-side recording technique provides a completely mono-compatible recording. This is the ideal technique for stereo recording if it may be broadcast in mono.

Step 1: Setting up the microphones

The mid mic is a directional mono microphone that is pointed at the center of the sound source, while the figure-of-eight mic is arranged so that it is aligned in the cardioid mic’s vertical axis, as close to the cardioid mic as possible. The figure-of-eight mic is pointed 90 degrees away from the cardioid mic with the positive (+) normal phase side of the capsule facing stage right (this is important when setting the stereo image from the front of house perspective) and the negative (-) reverse phase side facing stage left. The two mics must align on the same vertical axis as this technique depends upon the signals being phase-aligned.

Step 2: Setting up the recording program

In your DAW, set the mid microphone to one channel and the figure-of-eight microphone to a channel just to the left of the mid channel. Then record the source material. Copy the figure-of-eight recording to a track just to the right of the mid channel and invert the polarity. Pan the figure-of-eight channel on the left hard left and pan the figure-of-eight channel on the right hard right. Pan the mid mic to the center.

As the mid channel volume is increased, the stereo image becomes more centered. As the left and right channel volumes are increased, the stereo image becomes wider. Please note that it is important to keep the left and right channel volumes equal.

Audio-Technica has several stereo microphones with built in mid-side capabilities, such as the AT4050ST, the BP4027 and the BP4029. These are all equipped with independent cardioid and figure-of-eight elements configured in a mid-side arrangement with switch-selectable internal matrixing. The microphones give sound recordists the choice of selecting a left-right stereo output (wide 127° or narrow 90°) via the microphone’s internal matrixing system or choosing discrete mid-side signals for later manipulation.

If you have further questions about the mid-side miking technique, feel free to contact the Audio Solutions Department for assistance.

Read the next installment in this series: Part 4: Using the Blumlein Pair Stereo Mic Technique with A-T Microphones