For perspective, this now-discontinued loudspeaker was included in numerous
double-blind listening tests over several years. It always was a front-runner,
either winning or being in a statistical tie with the best competitors. So although
there are imperfections, one may conclude that this family of curves describes
a highly commendable standard of performance.
Figure 18.8a shows an active/equalized loudspeaker at an early stage in its
development. The well-mannered directivity seen here is characteristic of good
constant-directivity horns. If directional control is required, as in an acoustically
“live” room that cannot be altered, horns are an excellent solution, especially
since horizontal and vertical directivity can be independently manipulated.