RTFM (READ THE FINE MANUAL) !
24" max height for bass floor reinforcement AND keeping the tweeters BELOW ear level to smooth the treble response.
The treble response rises on axis and therefore should be slightly below ear height as they are designed.
So many people F Up on this and wonder why they don't sound very good.
Also pay attention to the port plug options as listed in the manual- one, two or no plugs depending on distance to the back wall.