Bill,

Similar to mics, all speakers have a certain sound distribution waveform. This is dependent upon cone angle and a few other factors. There is a website that will provide you with the basic information on speaker size and cone angle patterns, but I havn't visited the site for about five years, and that was three computers ago, so I no longer have their side address.

As for the Z-5500s, my best results have been haveing the satellites mounted about 5-1/2 feet above the floor when I'm performing at floor level. When I'm on a stage, they're positioned about 4 feet above the stage level.
As for the Barbettas, I generally position them about 5 feet above the floor at the bottom of the speakers.

Gary