I built my WO back in 2005, with a pair of DHM-108b, for use in my car.  It's 24x36, with the expanded throat opening.  I have used it in a few PA systems over the years.  Last night, I installed it in a "permanent" location inside the stage at my church.  It is almost completely enclosed in the stage, with the horn firing into two large cutouts that will be covered with non-adjustable furnace vents.  I am thoroughly impressed with the capabilities of this box!

I ran an RTA and a parametric EQ on it.  It has a strong peak at 80-100 Hz, but doesn't roll off until 40 Hz.  I flattened it out with an EQ.  I hit 110 dB at the front row (10-12 ft), and 100 dB at the back row, with ~525 Watts.  I showed the sub to a guy that builds PA systems (before it was installed) and he called it a "cute little sub" and wanted to sell me a pair of Peavey SP118.

I kinda like the hidden nature!  Makes you think...how is that much bass coming out of those main speakers?!?!  Plus, it shakes the entire stage!
We left room under the stage to upgrade to a 36x36 box if we so desired.