Spaced Pair Microphone Technique

Spaced pair stereo recording positions two microphones several feet apart to capture time-based stereo information. Sound arriving from different directions reaches the microphones at different times, creating natural directional cues that produce expansive stereo imaging.

Technique Fundamentals

The spaced pair approach relies on timing differences between microphones rather than directional sensitivity differences used in coincident techniques. When sound arrives from the left, it reaches the left microphone before the right microphone. These millisecond timing differences create strong stereo localization cues.

Spacing typically ranges from three to ten feet depending on the source width and desired stereo image. Wider spacing produces more expansive stereo, while narrower spacing creates more focused imaging. The 3:1 rule suggests spacing microphones at least three times farther apart than their distance from the source, though this guideline doesn’t always apply.

Omnidirectional polar patterns work naturally with spaced pair technique since they capture sound equally from all directions without the off-axis coloration of directional patterns. This results in natural, extended frequency response across the entire stereo field.

Polar Pattern Considerations

Omnidirectional microphones remain the traditional choice for spaced pair recording. Their smooth off-axis response ensures consistent tone regardless of sound source angle. The lack of proximity effect allows consistent low-frequency response at varying distances.

Cardioid patterns can be used in spaced configurations when room rejection is needed. Pointing both cardioids forward creates a quasi-stereo image, though with less natural phase relationships than omnidirectional spacing.

Figure-8 patterns in spaced configuration capture significant rear room sound. This can enhance recordings in excellent acoustic spaces but proves problematic in lesser environments where rear reflections compromise the recording.

Spacing Guidelines

The relationship between microphone spacing and source width determines stereo image character. For sources narrower than the microphone spacing, the stereo image spreads beyond the physical source boundaries. Sources wider than the spacing compress into the stereo field.

Drum overhead recording often uses spacing roughly matching the kit width. Guitar amplifier cabinets suit closer spacing proportional to the speaker configuration. Orchestral recording may employ spacing of ten feet or more to capture the full ensemble.

Height and distance from the source interact with spacing decisions. Higher positioning allows wider spacing while maintaining appropriate perspective. Closer positioning typically requires narrower spacing to avoid an artificially wide image.

Phase Considerations

Spaced microphone positions create inherent phase differences between channels. These timing differences that create stereo also cause frequency-dependent phase relationships that affect mono compatibility.

When spaced pair recordings sum to mono, certain frequencies cancel while others reinforce. This comb filtering can make mono playback sound thin or hollow. Critical applications requiring mono compatibility may need alternative techniques.

Careful spacing choices minimize worst-case phase interactions. Avoiding spacing that places the microphones at exact fractions of common wavelengths reduces problematic cancellations. However, complete elimination of phase effects in spaced recordings is impossible.

AB Configuration

The classic AB stereo configuration places two omnidirectional microphones spaced symmetrically about the center of the sound source. This arrangement captures a naturally wide stereo image with full-bandwidth frequency response.

AB spacing for orchestral recording typically ranges from eight to twelve feet, positioning microphones roughly over the outer sections of the ensemble. Pop and rock applications might use three to six feet for drum overheads or piano recording.

The simplicity of AB setup makes it accessible to beginners while its results satisfy professional requirements. Two identical microphones on stands at appropriate spacing capture remarkably natural stereo with minimal complexity.

Decca Tree Variation

The Decca Tree extends spaced pair technique with a third center microphone. The configuration positions a center microphone forward of two spaced flanking microphones, creating a triangular array.

This arrangement improves center image focus while maintaining the wide imaging of spaced technique. The center microphone fills the phantom center hole that sometimes appears in wide spaced recordings.

Originally developed for orchestral recording, the Decca Tree applies effectively to any wide source where centered focus and expansive width both matter. Drum overhead applications benefit from the additional kick and snare focus the center microphone provides.