Why low sensitivity speakers?

Pmwoodward - Why would a stiffer cone be less efficient? A more massive cone, yes. But a more flexible cone seems to me as if it would just do a poorer job of moving the air, thus requiring more amp power to produce the same volume. Isn't this why the ultimate theoretical driver surface would be both infinitely stiff and yet infinitely light (impossible in reality)?

What he said, and probably also because not enough attention has been paid to the potential of modified horn-coupling strategies in audiophile speakers (except in the SET fringe), as wide dispersion and flat power response have seemingly gotten priority over wide dynamic range and low distortion, for reasons unknown to me.

Cdc, IMO, there is no way to lay the differences you heard at the doorstep of driver material for sure - there are simply too many concurrent variables at work in any given loudspeaker design to determine which is responsible for what by ear. And BTW, were the two speakers you refer to set up in exactly the same system, and fed the same material?