The Science
If you wanted to design the Ultimate Loudspeaker, you wouldn't start with a box....
It is a strange fact that the science of loudspeakers has been almost entirely based on the assumption that the drive units should be mounted in a box. Thiele and Small have described in great detail the performance of a drive unit in a sealed enclosure, and a vented enclosure (Bass Reflex) and between them these two variants account for 99.9% of all loudspeakers produced today.
Yet the box has few advantages:
1) It prevents rear (out of phase) radiation from the drive unit from meeting the front radiation, and cancelling.
2) It is transportable.
3) It allows bass resonance to be used to supplement the output from the cone.
However, a box also has major disadvantages>
1) There is as much energy going into the box as coming out of it, which means that as the box cannot lose energy, it is re-transmitted through the walls of the box, through the port, and back through the cone, as distortion.
2) The pressure of air sealed in the box acts as a resistance to the movement of the cone-so the cone cannot behave as the signal requires.
3) The box has to be large to generate serious bass frequencies, making it ugly and obtrusive in domestic environments
4) Bass resonance is, in fact, distortion.
There is an alternative-read on.