The FMB can angle the speaker out a bit and since the port is at the top you can probably get 3-ish inches from port to wall...

I bet Axiom says 3 inches

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8