A true transmission line wouldn't fit in a trunk, that's where the chamber comes in. By adding a small compression chamber, you can effectively shorten the line length and add some power handling capability back to the subwoofer that you would lost with a true transmission line.
it is rich's design and it sounds great.. i cant explain the difference it made from my standard ported box..i watched it get built...it has so open area in it..just a small chamber thats it