Ever hear a group of unamplified musicians playing spread apart on a stage...anywhere? No phase or time allignment occurs. Hmmm...
Not true...
For instance, say a single French horn player is playing a note that has the fundamental in the woofer, and harmonics in the midrange, and even higher harmonics in the tweeter.
Do you want those harmonics to all be related to each other?
Or do you want the midrange to have the phase flipped?