what i know is just from what i have seen. trends in the way boxes are designed and weather they work or not. lol... I dont really know why the wave reacts the way it does but i have seen TONS of box designs. And actually that the part of Car Audio that i love the most. How the box is designed and why. So with that being said With the designs that i have seen, lets say for ported boxes, (since the ported part of a bandpass seems to act the same as a regular ported box) I have noticed that if the box is longer you tend to find the subs on the oposite side of the box as the port. This is because you want the subs to pressurize as much of the box as possible inorder to create the proper cone movement and in turn get the most sound out of it. If the sub is aimed directly at the port and they are that close to each other then the box isnt going to pressurize. Its like playing the sub in free air especially with the port as big as it is. So the location of where the subs are in the chamber is actually very important in loading and pressurizing the enclosure. Now with the 4th order I dont think the sealed side of the box is suppose to counter act the loss of pressure in the ported side. It may help with that. But as far as i know Its the part of the box that is most responsible for the lower end of the frequency range. Thats why they tune bandpasses alot higher than regular ported boxes to account for the higher range of frequencies.
I dont know if that made sense or not or if it answered questions in this thread. Thats just what i have seen. If you want look at alot of designs that RAM does and notice he doesnt just put the sub in the middle of the baffle. There is a reason he puts them closer to one corner than the other, or closer to one side of the baffle than the other. Most of what i know is observations.