FOSTEX FX120 BASS REFLEX PLANS
Below are the Fostex recommended box plans for the Fostex FX120 fullrange speaker. The bookshelf bass reflex plans are from the Fostex website.
Fostex FX120 Recommended Bass Reflex Enclosure
Fostex FX120 Recommended Double Bass Reflex Enclosure
The Double Bass Reflex enclosure drawing is from the Japanese* Fostex FX120 Datasheet / Notes (PDF - 536kB) which were included with the driver.
* I have assumed this is Japanese, please correct me if I am worng.