Waves B360 Ambisonics Encoder Plug-In (Download) - Manual (Page 4)

B360 Ambisonics Processor / User Guide
4
What is Ambisonics?
Ambisonics is a long-established standard for recording, mixing, distributing, and playing 360-degree sound audio. The
entire sound image of a space (360-degrees left and right, up and down) can be captured and encoded as a four-channel
stream.
Ambisonics differs from classic surround sound technologies such as Quad, Dolby Digital, SDDS, DTS, and others since
these formats create a surround image by sending specific mixes to specific loudspeakers. They can provide good
imaging when static, but as the sound field rotates, the sound tends to “jump” from one speaker to another. Also,
dedicated speaker systems are usually “front biased”: information from the side or rear speakers is not as focused as the
sound from the front. Ambisonics instead treats a soundscape as an uninterrupted sphere of sound around a center
point. This center point is where the microphone is placed while recording and where the listener’s sweet spot is located
while playing back. Ambisonic channels cannot be fed directly to speakers; they must be decoded for playback.
Ambisonics captures a full spherical sound image with four microphone capsules in a tetrahedral array. The raw signal
from these microphones is encoded to the four-channel “Ambisonics B-format,” which is the format used while mixing
and monitoring.
There are two conventions within the B-format Ambisonics standard: FuMa and AmbiX. They are quite similar, but not
interchangeable. Waves Ambisonics plugins use the AmbiX format. Ambisonic files that are FuMa B-format can be converted
with the enclosed format-changing plugins, which are described in Chapter 3. Below is the B-format AmbiX channel
sequence.
1 W Omnidirectional polar pattern. It contains all sounds in the sphere, from all directions at equal gain
and phase.
2 Y Figure-of-8 bi-directional polar pattern pointing to the left
3 Z Figure-of-8 bi-directional polar pattern pointing up
4 X Figure-of-8 bi-directional polar pattern pointing forward
Each of the three figure-of-8 microphones has a positive side and a negative (invert phase) side. Phase differences
between the four channels as well as gain differences, provide the sound information necessary to completely describe
the spherical sound space. Therefore, it’s very important that all B-format channels are processed together.