Soundfield B-Format Recording and Monitoring

Multi-channel surround sound recording has historically been a gear-intensive process, requiring a multi-track recorder and multiple microphones. One tool used to reduce the complexity of surround recording is the SoundField microphone system. SoundField is a single-point design, reducing complexity over multiple, arrayed microphones and their various microphone support rigs. SoundField microphones require four tracks for recording and record B-format program.

B-Format

B-format is, essentially, an intermediary format derived from the raw capsule signals. SoundField microphones use four-channel B-format to interface with recorders. B-format signals, referred to as W, X, Y, and Z, are typically recorded discretely. B-format decoders mathematically derive the target mix, whether it is mono, stereo, 5.1, or others from the 4-track B-format signals. An additional benefit of B-format is that the microphones on-axis direction can be changed without moving the microphone. It can be “steered” by mathematically using the four B-format signals.

Recording B-Format

Sound Devices 744T is a great companion to a SoundField ST350 microphone. The outputs from the ST350 preamplifier/control unit can interface directly to the line-level inputs on the 744T. The W, X, Y, and Z signals from the SoundField mic are connected to inputs 1, 2, 3, and 4, respectively of the 744T.

Monitoring B-Format

Because the B-format signals recorded by the 744T need to be decoded to some other format to be meaningful, the 744T has a B-format monitoring mode. B-format monitoring is selected from the headphone output Setup Menu option. When listening to the SoundField microphone, the 744T’s B-format monitor builds a stereo mix using the W, X, and Y signals. For more control in monitoring the SoundField, the ST350 controller includes a more flexible headphone monitoring system.

While customers with earlier ST250 SoundField microphones can use the 744T for recording, the ST350 preamplifier outputs are a better match for the gain structure of the 744T.

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