Hi Mojo,
It is really about total radiated sound power. If someone is facing away from you, you can still hear them speaking, even in an anechoic chamber. A speaker works the same way and one of the most important set of curves about how a speaker will sound is the sound power average of curves. It's close cousin, the directivity index, is also important. By having drivers mounted on the rear of the speaker with a separate amp channel being controlled through a DSP we have almost endless control over every curve radiated from the speaker all the way around that make up the sound power and directivity index.
