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?