[sdog21]

Not sure If im modelling this correctly. This is telling me that I'd have to go up to 600W per speaker to hit Xmax. I've read in other places that 250-350w would be the most you'd want to go with dual opposed IB318 subs to prevent from bottoming out.

 

[BP1Fanatic]

Have you tried modeling the speaker with other software? I use Hornresp, WinISD, and a modified version of Brian Steele's bandpass.xls which he has replaced with Hornresp on his diysubwoofers.org site.