Hi Archie,
The Wild Burro Audio Betsy driver is rated at 92.4 db efficiency.
Something Steve told me that I honestly didn't know is that the dipole configuration adds to the efficiency ..... as much as 3 db.
That probably explains why a pair of Betsy baffles fills the 35' x 17' listening room at my storefront with music being powered by a Decware SE84UFO amplifier. The room has an 11.5' ceiling, as well.
The drivers have a 5.9 ohm impedance and no crossover components which also makes them very Zen amp friendly .....
I have a page on my website that answers some common questions about the Betsy baffles. It can be found
here.
Best wishes,
Randy