very efficient, horn loaded drivers can extend frequency response by anywhere from 1-3 octaves on the low end, if done correctly they dont sound "trumpety" big with people using tube amps because of the low output of them they need speakers with as much efficiency as possible. i know a guy who has horns with a 99db efficiency and using his low power tube amp he can reach levels high enough to permanently ruin your hearing. they usually work best if you mount a separate tweeter in its own enclosure not in a horn because horns do weird things to high frequencies (if they arent designed right they will "ring")