Suppose we build a linear array forming an equilateral triangle with the centered listener, as in typical stereo speaker placements. Denote the side-length by . The listener distance is then from the array. Suppose we want to sit back three meters from the array for normal listening. Then , which is about 7 HOPs across, following the example of Fig.13. To reduce edge effects, we can add one more HOP on each side to obtain nine HOPs, as shown in Fig.14. As discussed in §4.6 on page , the five-band HOP places the crossover to VBAP/stereo at Hz, or lower as discussed in §4.7 above, and the subwoofer nominally crosses over at 80 Hz, or wherever the VBAP/stereo band lower limit may be.