The JBL construction guide suggests a 2 cu. ft. enclosure for a single 2206H tuned to with a 4" duct 7.6" long. Two questions:

What should the length be if I chose a 3 in. duct instead?

The 2206H data sheet shows good response tuned to 50 Hz in a 2 cu. ft. box. What would the corresponding lengths be for a 4 in. and for a 3 in. duct for 50 Hz tuning of the 2 cu. ft. box?

Application is for HT with LF crossed over to sub at 60 to 80 Hz. Thanks.

John Y.