Stereo Microphone

Stereo Microphone Technique

A stereo microphone technique combines two mic capsules in a single housing for conventional stereo recording. The type of microphone used for this combination can vary, from condenser to dynamic to ribbon microphones.

Stereo Miking

One of the most popular specialized microphone techniques is stereo miking. Using two or more microphones to create a stereo image gives depth and spatial placement to an instrument or overall recording. There are several different methods for stereo miking. Three of the most popular are the spaced pair (A/B), the coincident or near-coincident pair (X-Y configuration), and the mid-side (M-S) technique.

The Spaced Pair Technique

The spaced pair (A/B) technique uses two cardioid or omnidirectional microphones. Furthermore, they are spaced 3 to 10 feet apart, panned in left/right configuration to capture the stereo image of an ensemble or instrument. Effective stereo separation is very wide. When the program switches to mono and frequencies jump out or fall out of the sound, you can assume that there is a phase problem. This may be a serious problem if you play your recording in mono. Finally, this is typical in broadcast or soundtrack playback.

X-Y Technique

The X-Y technique uses two cardioid microphones of the same type and manufacture. They have two mic capsules placed as close as possible (coincident) or within 12 inches of each other (near-coincident). Also, they face each other at an angle ranging from 90 to 135 degrees, depending on the sound source's size and the desired sound. The pair is placed with the center of the two mics facing directly at the sound source and panned left and right. Due to the small distance between the microphones, sound arrives at the mics nearly simultaneously. This reduces (near coincident) or eliminates (coincident) the possible phase problems of the A/B techniques. The stereo separation of this technique is good but may be limited if the sound source is extensive. Mono compatibility is fair (near-coincident) to excellent (coincident).

Mid-Side Stereo Technique

The M-S or mid-side stereo technique involves a cardioid mic element and a bi-directional mic element. Moreover, they are usually housed in a single case, mounted in a coincident arrangement. The cardioid (mid) faces directly at the source and picks up primarily on-axis sound, while the bi-directional (side) faces left and right and picks up an off-axis sound. The M-S matrix combines the two signals to give a variable-controlled stereo image. By adjusting the mid versus side signals level, you can create a narrower or wider image without moving the microphone. This technique is entirely mono-compatible, and producers and engineers widely use it in broadcast and film applications.