d&b 16C - Manual (Page 6)

2.1.2. Dispersion characteristics
The following graphs show dispersion angle over frequency of a
single cabinet plotted using lines of equal sound pressure (isobars)
at –6 dB and –12 dB.
Isobar diagram 16C vertical
2.1.3. Directivity index (dB)
Isobar diagram 16C horizontal
d&b 16C Manual 1.2 en 6