Hmmm,...good question. Don't know. I have never seen anything (articles, reviews, spec sheets, etc) to indicate any difference in the 12" SE/R, LSE or SE driver. I would assume they are the same. I also would not take the 305mm and 307mm to mean anything. The Status Acoustics web site lists the driver as 300mm, the RBH site shows the 305mm for the SE and 307mm for the SE/R, but some other RBH reference material I have shows them both to be 305mm???
If you really need to know, I'd suggest you call RBH.