Upper, Middle, and Lower HOPs

Figure 14: Three rows of nine HOPs $\approx 3$ m high and $4.5$ m wide

Figure 14 illustrates a simple extension from one to three multiband line-arrays for the purpose of providing three elevation levels. In the vertical dimension, it can be driven as three-channel VBAP, or stereo with a center channel. While azimuth perception is accurate to $\approx 1$ degree straight ahead, elevation perception is an order of magnitude less accurate, so a cruder sampling of the vertical axis is appropriate.