Does anyone know if the SPL ("efficiency") listed by other speaker manufacturers is anechoic? If they aren't, then the Axioms as a brand are very efficient speakers. The other brands typically only give a single number while Axiom provides both. I was curious in comparing the specs among Axiom, Polk, KEF, etc.

Most speaker brands publish the in-room sensitivity/efficiency specs unless otherwise noted, as far as I understand. Yes, the Axioms are efficient speakers.