it's about 70".
It's plenty for one sub. Hell i have 4 18's with 118" of port and it sounds so good i haven't had or wanted to build a new one in 11 years now. I hope it sounds good though, i will know tomorrow or the next day.
DAYUM? Ive always been curious why you ran such a small (relatively) port compared to so many other multi 18 systems. isn't that like 6 sq inches per cube for your enclosure? What was your though process behind that port size. It obviously works very well.