The soundstage height of the SoundLabs is normally ear height, or a little above ear height. If you're sitting, then it's at seated ear height. If you're standing, then it's at standing ear height. If you sit on the floor, it's at seated on the floor ear height.

I think this is because the first sound from the line source panel to reach your ears is that which travels the shortest path, and so the vertical image height is derived from this shortest-path first-arrival signal.

Now if one SoundLab panel is leaning forwards or backwards a little bit more than the other, it can screw up the imaging more than you'd expect. Best to get them both at the same vertical angle.

The reason the image height is sometimes slightly above ear height is due to a phenomenon first documented back in the early 30's (if I recall correctly) and subsequently confirmed by multiple researchers. That is, the ear has a tendency to mistakenly localize the height of a high frequency sound source slightly above its actual height. So if the program material has a lot of high frequency energy, the soundstage height can seem to be bit higher than normal.

Duke