Ah, thanks, I see that nowJust_a_fan wrote: ↑18 Feb 2021, 12:28
No, on a heavily reflex diffuser such as fitted to the T.50, you get separation at all speeds because the change in direction is too big for the air to follow it naturally. The fan works against that to remove the dirty air in the reflex section and make the diffuser work better at all speeds. There's a nice little video earlier in the thread where Murray shows this on a white board.