My hometheater is getting close to being finished, and I am gearing up to build my final subwoofer. A while back, I posted a thread asking for help, and this is what I got. I am planning on building a coffee table sub, with 4 tempest drivers that I bought back in the preorder stage. I am going to build the table to house two sets of clamshell type iso setups (downward firing). I am looking for a Q of around .577. DanW wrote that if I have a net 220 litres, with (2) 4" flared ports 34 centimeters long, I would acheive a nice, low tuned sub. However, I just wanted to check things about before I started cutting, and put this info into the software available on adire's site, and came up with a -3db at 35 hz? Obviously, I'm doing something wrong? Any help would greatly be appreciated, should I just build with what he said, and hope my results are good? Thanks in advance.