It wouldn't be my first choice to use the 2225H in Cubo Kick 18 but it can be done, it's Xmax is on the small side for Cubo 15 so Cubo 18 is abetter choice. If the 3 cm depth difference is that important you could add 3 cm to the front of Cubo Kick 15. Alternatively you could also use the 2240H in Cubo Kick 18.
Both 18's drivers are suited for Cubo 18 Extended. The 2242H will take the most power as it has plenty of Xmax, for the 2240H I would use a 40 Hz high pass and around 500 W of amplifier power as it's Xmax is somewhat limited.
I believe they do meet all of the requirements outlined in the spec advise above. What I'm keen to know if whether the parameter advice when selecting standard or extended are the same as for the Cubo 15? As such if Vas * Qts for this driver comes in at 54.95 then the extended box should be used?
The parameter based selection advice for standard or extended is the same as for Cubo 15, so Cubo 18 Extended in the case of the 18NW100-4. I once build a Cubo 18 Extra Extended but found Cubo 18 Extended worked just as well.
Hey Cubo after you helped me and everyone else here so much, i thought you might be happy about some building Pics. I built 4 Cubo 18 extended in February and also did some measurements, which i uploaded as pictures too. If you're interested in the measurement data for group delay, distortion, etc. just tell me and i will send them to you.