Steve, I have always considered the rule of minimum 1 port diameter away from any obstruction, it makes just as much sense as port end correction when doing a slot port using a wall of the enclosure. But what specifically are the effects of using only exactly 1 port diameter? Is there an end correction number for that? Obviosely anything less just shouldn't be done, that's like making a 10" diameter port but sliding an 8" diameter ring into it part way...bottle neck....
finally got internal dimensions measured from the inside... from the outside it looked like I could easily go 34" high, but not even close. 28" tall, 28" deep (not 24") and still exactly 48" wide.
So now I am down to 17-17.3 cubes with port, sub, and 2"x4" bracing taken into account. I'm going to have to go with an 8" port rather than the 10". Tuning between 18 and 20Hz. Variance is on whether I go with the 7 3/4", 8 1/4", or 8.75" sonotube.
Here is a freeair vid of Bassotronics Bass Mechanik's Bass I Love You. I didn't realize there is about a 5Hz tone as well as the 15Hz. The camera refresh rate makes them look the same.
This IB3 18 is amazing, I am looking forward to the 22".