A HT buddy and I are planning to build some sonosubs. I'll be cannibalizing my sealed DVC sub for the driver and amp. For a long time I've pondered the differences between the Manufacturer's T/S parameters and the Dumax results provided on the PE website. Specifically the manufacturer lists a Vas value (4.25 cu ft) that's 25% larger than the Dumax measurement (3.4 cu ft). Which do you use and why? My impression is that when building sealed subs people tend to go with the smaller Vas as it allows a smaller box size (typically 1.1 - 1.3 cu ft stuffed). But when building vented subs they tend to use the larger Vas since it allows a larger box size and easier porting. So far I've just averaged the T/S specs and gone with that. The current plan is 90 liter enclosure with a full-length 4 inch flared port (18 inches long). That should put tuning somewhere around 22-23Hz. Any opinions? My first instinct was to mimic my SVS 25-31PC sub's alignment. But it got a little confusing when I realized that the PC has to be under 80 liters net and uses 4 inch flared port that's only 14 inches long. Hardly stuffed at all, I can't see how they get 25Hz tuning. That port should be at least 17 inches long.