I'm considering a sub project at the moment. I don't yet want to get bogged down in a detailed discussion of what I'm trying to do until I know it's feasible - but I will need to tune a relatively small box (1.3 cu ft) to a very low frequency (22Hz). For a 3" diameter port, the port length will be about 36", a ratio of 12:1, and will require a couple of 90deg bends to fit in the box. I am aware that I need to allow for the port volume within the internal box size. I've come across various suggestions for a limit to this ratio from 2.5:1 to 4:1. What is the audible or physical effect of having such a long port? Has anyone ever built such an enclosure and gotten satisfactory results?