we've been chatting on the full range driver forum, seems it is a newer eminence b102, works well in 2.5ft3 tune to 50hz I think. You can either run a 6db slope at 5khz on some tweeter (hopefully rugged, the apt80 is not as good as they used to be). Ron used one of the selenium compression drivers. Another way is to run a 12db with a tweeter (such as the ribbon in the Zu essence).
Tekton made a similar design called the Uruz that I wanted to clone. But I'm usually doing 4 different things and never finish a single one !!!!!!!!!!
According to my simulations pipe lenght = quarter wavelength of the driver's Fs (about 65 Hz for the Druid) and very strong motor should be ideal. Commercially available fullrange drivers have too low Fs. A 10" pro mid that can be used without lowpass is the Ciare PM250.
A ready-available design for that driver is the Lilliput-Horn (send a PM to Cantare for questions). Bigger than the druid enclosure but without the 200 Hz cancellation. I would replace the bullet tweeter with the Gradient GRT-195 Mk2.
freddiy has used the 10" Eminence b102 already mentioned and tested it. Seemed to measure similarly to the Zu driver. He used the matching Eminence tweeter too. But Zu modifies these drivers for their designs making them unique. It is a nice looking speaker imo.