Stereo Miking Technique Reference

Reference: STEREO-MIC-01. The existing "3:1 Rule" tool on this site is about avoiding phase problems between separate mics on different sources — a completely different problem from this one. This is about deliberately configuring a matched pair of mics to capture a stereo image: overheads, piano, choir, or ensemble pickup.

Technique	Setup	Notes
XY	2 cardioids, coincident (capsules as close together as possible), 90–135° apart	Fully mono-compatible (no time-of-arrival difference between capsules) — the safest default when you're not sure the mix will stay stereo.
ORTF	2 cardioids, 110° apart, capsules spaced 17cm (7in)	Blends level and subtle time differences — wider, more natural-feeling image than XY, still solid mono compatibility.
NOS	2 cardioids, 90° apart, capsules spaced 30cm (12in)	Similar idea to ORTF with a wider spacing/narrower angle balance — a matter of taste between the two.
Blumlein	2 bidirectional (figure-8), coincident, 90° apart	Captures a lot of room/ambience via each mic's rear lobe — great for a live, spacious sound, less useful if you need to control bleed.
Mid-Side (MS)	1 cardioid (mid, facing the source) + 1 bidirectional (side, facing 90° off-axis)	Decoded post-capture into L/R (see diagram) — the width is adjustable after the fact, and it collapses to perfect mono automatically by just using the mid mic alone.
Spaced pair (AB)	2 cardioid or omni mics, no fixed angle, spaced 1–3m (3–10ft) apart	Big, wide image with a real sense of depth — the tradeoff is weaker mono compatibility, since the spacing introduces real time-of-arrival differences between the two mics.

Mid-Side Decode, Briefly

MS is worth calling out separately because it's not just "point two mics and pan them" — the side mic's signal gets duplicated, with one copy phase-inverted, then panned hard left and hard right against the mid mic's center-panned signal. That's what "decodes" the raw M/S capture into a standard L/R stereo image, and it's why MS is popular for broadcast and live use: you can adjust the width by changing the side channel's level relative to mid, after the fact, without moving a mic.

Sources: Shure Incorporated, Microphone Techniques for Live Sound Reinforcement, pp.32–33 "Stereo Microphone Techniques." Boyce, Teddy, Live Sound Reinforcement, §12.9 "Stereo Miking Techniques." Rewritten in Ryan's own words from the source material.