Like two Altec 3182 woofers (18 inch, Fs=18, Qts=0.4, EBP=45)http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3702903562&category=47094&sspagename=STRK%3AMEBWN%3AIT&rd=1
In a closed box approximately 7 ft^3, they're F3 at 40Hz, -6dB at 30Hz
Vented at 30 ft^3, they're F3 at 20Hz
Now 30ft^3 does approach difficult to accomodate in a domestic situation (to put it mildly), but would it be worth it vs. 6dB of EQ in 7 ft^3 to flatten the response to 30Hz (probably not even that much boost with room augmentation)?