High efficiency or perhaps more correctly high sensitivity unto itself is an admirable attribute. High sensitivity can play louder, tends to allow lower amplifier distortion, reduce power requirements and ergo reduce cost,size, weight and heat. High sensitivity also allows more noise into the signal. On the other hand it’s easer to create a steady lower impedance than higher one. A steady impedance is easier on amplifiers, reduces the potential for phase angle challenges, and frequency response linearity deviations. There are many considerations that go into speaker design, balancing them all sometimes requires sacrificing the ultimate capabilities of some attributes in order to better accommodate other considerations. How many commercially available high efficiency loudspeakers capable of time and phase coherence can you name? How many high efficiency speakers can demonstrate a good step response or square wave?
