I would like to know how you calculate air space for inverted subs. Is it any differant? I know that boxes for inverted subs are alot smaller than the traditional way.
The volume equation is LxWxH/1728. Most manufacturers list what the box size should be w/o having to calcule driver displacement, so that you don't have to add driver displacement to the volume of the box if you build your own. This means if a manufacturer lists a box size of 1.25 cu ft, you should build it 1.25 cu ft, and not worry about how much airspace the sub takes up. In this example, inverting the sub will call for 1.25 cu.ft minus the sub's driver displacement. Find a PDF on your sub and see what the driver displacement is, and subtract that from the recommended box size.