@Toid No problem. I just appreciate all the advice!
Great catch on the port length. I must have been playing with too many options. You are spot on, I get 38.5″ after checking again.
I am excluding the port from the internal volume. The blue lines below show the cross section that I am using to calculate speaker volume. And the red line shows how I am measuring port length (based on one of your videos). Let me know if those look correct or not.
Now that you found the port length error, I am trying other designs. In general, how much can you push port velocity? I’m looking at making the box a bit bigger (4.5 cu ft), and going with 3 ports 1.25″ x 7″ x 32.25″. That has a peak of about 25 m/s for port velocity.
I’m assuming that I should try to keep the tuning frequency of the box at 21.21 Hz for this driver? Or should I push that up a little bit?
And, back to the sound dampening question … do I need to add foam on the inside and, if I do, do I need to make the box bigger to account for the volume of foam?