You have no idea what you are talking about
Op you are probably going to want to go with a 4th order it will play extremely flat if designed right stick to a 2:1 or 3:1 ratio any higher than that the peak will be too high for what you want you want to start with massive port area and shrink it down to get the sound you want a good timing point to start at is ~45hz I am currently designing a 4th order wall for 4 sundown Z 18s
thanks zayres.