The recording angle, explained

The recording angle is one of the most useful and most misunderstood numbers in stereo recording. It answers one question: how wide a slice of the sound stage ends up between the two loudspeakers?

The definition

Take a stereo microphone pair and a sound source that moves from the centre line outwards. At some angle, the source is reproduced fully in one loudspeaker. Twice that angle is the recording angle (often abbreviated SRA, for stereophonic recording angle).

• A source inside the recording angle appears somewhere between the loudspeakers.
• A source outside it appears hard in one loudspeaker and no longer moves, however far out it goes.

So a recording angle of 100° means the microphone sees 50° on each side of its centre line that map onto the loudspeaker base.

It is not the pickup angle of the microphones

Two things often get mixed up:

• The pickup pattern (cardioid, figure-8) describes how each capsule responds to sound from different directions.
• The recording angle describes where a source ends up in the stereo image after both capsules and both cues are combined.

A pair of cardioids at 90° and a pair at 110° with 17 cm spacing have very different recording angles although the capsules are the same.

What changes it

Typical values from the standard setups: XY cardioids at 90° give roughly 190° or more; ORTF about 96°; NOS about 81°; Blumlein about 76°.

Matching the recording angle to the ensemble

The practical use is the fit between the recording angle and the angle the ensemble covers when seen from the microphones:

• If the ensemble covers more than the recording angle, its outer players crowd into the loudspeakers and the edges of the image look squeezed.
• If it covers less, the image is narrow and does not use the full width.

You adjust the fit with the distance: move the pair closer and the ensemble covers a larger angle; move it away and it covers less. Distance also changes the balance between direct sound and room, so the trade-off is not free.

Try it

Use the orchestra and ensemble angle tool to compute the angle an ensemble covers, and the stereo recording angle tool to see where the outer players will appear.

Draft: written by an AI assistant, awaiting technical review.