OK, I can explain this.

The article references the original EP0 design, which used a single woofer behind a passive radiator and a larger cabinet. The currently shipping EP0 uses a single woofer in an M3 cabinet. I believe that the performance is similar, although I've not compared the two back to back, as the older subwoofer is not compatible with the newer amp.

I am the Doctor, and THIS... is my SPOON!