OK, this amp has been out long enough now that people might be able to offer some speaker advice. I hope :)
I have the head and will play it through a 1x12 semi-open cab (actually initially I'll put the speaker into a vintage Crate 2x12 combo that I have lying around, leaving the other speaker either in place, or close the baffle). I generally prefer American-voicing, but as many will know, the BB15 has a fairly dark clean tone, and the OD settings place it squarely in Tweed or Marshall territory. My style is Gilmour, classic rock, and blues, with some roots country. Usual guitars are a Tele, 335, and a vintage SG.
I've read though most of the posts in this forum, and diligently watched Vaughn's videos (thanks for doing those btw as they're invaluable). My initial speaker choice was not a WGS but was the Emi GA-SC64 but I've been recommended the ET-65 and personally I've also liked the C12C/S and the Reapers. Now based on the various comments throughout this forum some suggest that the ET-65 and the G12S would not complement the darker nature of the BB15. The thing is that I'm looking to enhance the Fender shimmer that I can coax out of the amp, while also providing the right platform for the warm OD sounds. So is the Reaper the right choice, or should I nevertheless go with the one of the two others?
I'd very much appreciate any thoughts as I REALLY need to buy a speaker to start getting the most out of this great amp!
Gotcha ... and what you are describing leads me to only one speaker ... the Retro 30! It'll have tons of that fender chime/shimmer ... and the bottom end is solid as a rock in that (mostly) open-back cab.