Jbl 4818 and ports

i am the possesor of 3 jbl 4818, in fact 1 is jbl and the 2 other are replicas from atelier 33 a french manufaturer, My problem is that i think the ports are too small. So i need your help to figure this out !

The 2 non jbl seemsto work a little bit better, almost no air noise from the ports, but the jbl one that has smaller ports makes a lot of air noise. They are all equipped with RCF's l18s801. I even think it is possible to recalculate new ports.

Thanks for you help  !