The way I figured was
46.5w x 18.5d x 25.75 =(12.81cuft)
Port volume I did
8.25h x 18.5w x 20d =(1.76cuft)
12.81-1.76= 11.05 cuft
11.5 - .42(subs) - .4(bracing) = 10.23 cuft @ 34.5hz
I appreciate your help. I am trying to figure out the most accurate way of doing it. I did use a port length calculator but...