19 omnis in close proximity?? How would that work?
Differential sum/delay processing is integral to these systems. The key word in searching for information on how this works is
beamforming. It uses carefully manipulated phase cancellation and reinforcement to create higher order patterns with more tightly focused primary directional lobes than can be achieved with single first-order microphones. The approach applies to both sensing (microphone arrays) and generation (loudspeaker arrays). The tradeoff for the increased directionality is increased noise, spatial aliasing, and funky off-axis behaviour. With a few exceptions, these types of beamforming arrays have historically been used primarily for measurement purposes and teleconferencing applications rather than music recording.
These systems typically use omnidirectional nodes for the most part, and can either be designed with arrays of those elements embedded in a surface (like the Zylia, and the 32 element Eigenmike) or suspended in free space. 3-dimensional arrays are usually either embedded in a rigid sphere or wire-frame supporting arrays. Planar arrays usually have the elements arranged in either a regular grid pattern, spiral arms, or randomly arranged.
Zylia's older brother, the 32 omni element Eigenmike-
The Trinnov SRP system is one of the few marketed for high quality surround recording of music, providing high-order directivity across the horizontal plane using eight omni elements in a sort of horse-shoe arrangement which I speculate is designed to increase order directivity in the forward direction more than other directions. Would you like that with 8 DPAs or 8 Schoeps omnis?
When this is applied to higher order ambisonics, channel count rises rapidly with increasing order.
1st order ambisonics requires 4 channels for full periphony (all directions), 3 for a single plane (horizontal only, as in double mid/side)
2nd order ambisonics requires 9 for full periphony, 5 for single plane
3rd order requires 16 for full periphony, 7 for single plane
etc..
Check out this 64 node single plane grid array of B&K measurement microphones-
I suppose we should update the
Surround Sound Microphones list thread with the Zylia and OctoMic.