Efficiency = Performance is rediculous.

"The only reason to NEED more power is bad speaker design - Higher efficient speakers ALWAYS sound more dynamic more lifelike..."

" maybe a reason this 1940's K-Horn is STILL being sold is because it's probably one of the best 10 speakers ever built by anyone."

If efficiency were the standard of performance, a Volkswagon Beetle would be a much better car than a Ferrari and a Rolls Royce. It gets much better gas mileage hence it is more efficient.

Maybe the real reason Klipschorn is still manufactured is that it is regarded as the Founder's claim to fame 65 years ago and is heavily subsidized by profits from much more modern and successful designs offered by the same company. In the late 1950s AR1 clearly demonstrated that it could produce much deeper less distorted bass in fact about an entire octave lower at around a fifth the cost and the space. These enormous dinasaurs are museum pieces. Few serious manufacturers of high fidelity loudspeakers actually use horns anymore for midrange and treble because of their poor dispersion and uneven frequency response. Only a handful of diehards are wedded to them. Their one legitimate use is in being able to produce an acceptable sound level from puny antiquated amplifier designs like the SET. It is sad to see so many people nostalgic for the obsolete technologies of a time that existed long before most of them were born. Why were these techologies abandoned? Because better ones replaced them, that's why. Same as in every other area of life.