71 dB
Headphoneus Supremus
You know what 71db, you are correct, I take that back (partially) because my own center speaker has no flat bottom (due to curved cabinet) and comes with rubber pads, a bit like the IsoPods that accommodate the curvature of the speaker. They allow for a slightly inclined angle, and alleviate surface reflections from whatever might be holding the central speaker. I'd say that these are workarounds for compromised issues from the start, and those especially relevant to center speakers because they often have to be placed on top of or bottom of a screen. The inability to place at ear level, horizontal dispersion, and fact that they often sit on shelves or inside of media centers, makes acoustics all the worse. But never mind that, I don't mean to go on about center speakers. The point is, yes, in certain compromised circumstances it is a good idea to tilt speakers up.
What a nice and matured response!
It's indeed the general idea that you can tilt your pc speakers or center speakers up to compensate challenging acoustic environment and location. Normal hi-fi speakers are supposed to be located so that there's not need for tilting (acoustically good places and on correct altitude).