This is about Logitech z2200 specifically. I guess with 15" speakers or something like that, they are parallel to floor and that works.

As for z2200 (probably z5500 as well), I see the speaker angle to horizontal is about 30 degrees upward. This is relative to the Logitech stand that is part of the speaker housing, which I have mounted on a horizontal platform.

So, what height off ground (audience ground level) do you think the speakers should be positioned? Or no concern at all?

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