Just picked up a 5-string bass to add to the collection, with low B at 30.87hz. It's the now-discontinued match to my 4-string Epiphone EB-3L. All these basses have solid necks glued into the body, (on the Rickenbacker, it goes all the way through the length of the body!), so they all have great low-end resonance.
I was originally planning on a cabinet with the JBL Sub1500 tuned to 40 hz, plus an E110 in the doghouse for mids/highs, but 'looks like I'll have to change my design plans... (Sub1500 is in a 4628B cabinet right now, with 2118H.)
John