While I've never seen or heard one, the SoCal-based luthier James Tyler (
www.tylerguitars.com) offered a bolt on six-string tuned F# thru G. Possibly you could contact him for more info. I'm sure there must be others. Mica could fill in if ALEMBIC ever built or considered one. Tyler could tell you where he got strings for it.
Tyler makes very sophisticated bolt-ons favored by big gun session guys like Stubenhaus and Abe Laobriel. They're not to my taste but are probably among the most innovative bolt-ons I've ever seen. Several Nashville guys use them here in town on record dates as well.
The fundamental of that low F# would be in the mid-20hz range. I guess it would all depend how much of it you want to hear, as typically we percieve the fattest, bassiest tone from the first several harmonics building on the fundamental. I doubt you'd hear much of it through a Super Redhead or Metro. It's gonna take a lot of power and drivers if not reinforced thru the house system. A LOT of cabinets quote response into the 20's, but this would really be a 'put up or shut up' test !
I'd imagine if you'd REALLY want to get as much of it as you can, you better get up with BagEnd (
www.bagend.com) and invest in some of Ron's ELF technology. This is an ingenious, 'outside the box' technology that truly renders deep bass in a remarkable, clear, and musical fashion. No doubt that with ELF it would be as usable tone . . but VERY low.
