Hi,

I have the Q4s.
When mounted, the BOTTOM of the speakers is exactly 3 inches below the bottom of the mount.
This should allow you to measure the the distance from the ceiling to the top of the speaker.
Mine are 63 inches floor to speaker bottom and 21 inches speaker top to ceiling.
Hope this helps. (I'm assuming Axiom is using the same mounts for the Q4 / Q8s).