I'm about to tackle a DIY subwoofer build. I'm totally comfortable with the woodworking but want to make sure I understand the acoustics, so I have a few questions: - I've been playing around with a subwoofer box designer from http://www.ajdesigner.com/speaker/index.php. I input all the parameters of my driver, but I want to make sure I understand Qtc, which isn't on the driver spec sheets. I can pick the value that I want for that, right? And depending on what I pick, I will get a different optimum volume and a different rolloff response? - If I want to build a dual-driver opposed design (sealed), do I just double the sealed volume I compute for a single driver? or is it more complicated than that. - Once I have my desired volume, should I add any loose fill or padding, or is that only for enclosures that are undersized? - I'm toying with the idea of a non-rectangular enclosure (maybe a trapezoid), mainly for aesthetic reasons. Is that going to help or hurt the performance? Or does it not matter as long as the volume is correct? Thanks for the help!