my subsonic is set to 25hz....
Which would mean your box needs be tuned at 27-28Hz to be effective...and there is no way the port is 45" long to yield a 27Hz tuning
I'd suggest getting an adjustable filter.
lol my box is tuned to 28hz...
OOhh and FYI port dimensions=9x23x37...
how many cubes is the box?
well id half to dig up old google sketch up plans but i believe 12cuft..