[Bad70sbchevy]

It all depends. There are two types of boxes, ported and sealed. Ported boxes have openings in the box that allow the box to "resonate" producing more base at a specified frequency depending on the opening. You can get very carried away with different formulas for tuning these kind of boxes (sometimes the manufacturer will give specs for a typical opening), but the simplest boxes and most popular is the sealed box (what I did). These boxes have to be air tight or sealed to work. As for the box volume, usually the manufacturer will specify a volume for the box. Shape usually doesn't matter, or if it does its not enough to make a difference generally. One thing to note though usually the manufacturer gives a range of volumes. Smaller volumes produce tight base which is good for rock music and bigger boxes tend to give a loose or lower base typically perfect for rap music.