Extending the four-way Huygens Array of §4.5 to five bands, and enforcing octave-band design all the way down yields a five-band Huygens Octave Panel for our consideration.
Figure 13 shows the driver outlines for two five-octave HOPs side by side. Each panel is about half a meter wide, so a 4m wall needs 8 HOPs.
The top three rows use drivers of the same sizes used in the Kenwood JL-840W four-way speakers (3, 6, and 12 cm), while the fourth row is reduced to 24 cm (down from 30 cm) in order to continue the octave divisions, and a fifth row is added employing 48 cm (19 in) drivers. Fifteen inch speakers are very common, and could be used as a compromise for the bottom row, and subwoofer drivers of diameter 18 and 20 inches appear to be available, but probably quite expensive to use in an array system.30