PJSprog maybe downplays it a bit. These are really acoustic in name only.. You need an amp even to sit in with a steel string dreadnaught. Bad enough with a 4 string, but an open B...
When all instruments were acoustic, the Contrabass was made gigantic and played with a bow to be heard in the orchestra. These days when I see a stand up bass with a jazz or bluegrass band it's a 3/4 size and has a pickup with an old 400RB or 800RB amp to be heard. In Miami I only hear Mexican mariachi bands playing truly acoustic. To keep up with with a trumpet, violin and a chorus of Mexican guitars you need a "guitarrón". I have tried to play a couple of these... very high action and it feels like you have a Volkswagen sitting on your lap.
I've never heard one, but it seems that the Russians have also not solved the size problem.
In both cases the lowest note corresponds to a low E string on a bass guitar.
(I would love to find a cheap contrabass balalaika, which is tuned like the 3 lowest strings on a bass guitar... I have given up on the guitarrón as ridiculously hard to play...but have huge respect for the guys who still do.)
The only fully acoustic basses that I know of that go lower are full-sized contrabasses with an extended 5th string which is usually tuned to C but occasionally to B.
But so much for answering the question you didn't ask! I would be tempted to try steel flatwounds, which is what you find on most uprights ;-)