Horns do it better

 
    Horns have been used for sound amplification for thousands of years.  Horns are a effective mechanical means of coupling the the sound reproducer to the air. They operate by converting high pressure, low volume sound waves into low pressure, high volume waves.
    Even though horns have been used for so long, how sound actually propagates from them is still not fully understood. The mouth and throat diameters, the overall length, and the amount of flare all have a effect on the qualities of the amplified sound.
   Some of the best sounding speakers ever made have been horn loaded, but so have some of the worst. Usually the later is caused by compromises made to the design due to aesthetics or cost control. Designing a horn that can play all the full spectrum of human hearing is the holy grail, but basic horns are limited to only playing about 3 octaves in range. As the human ear can hear over ten octaves, a speaker should require at least three separate horns to cover the range. A way to "cheat" is to use different flare profiles, or a combination of flares. Types of flares include conical (megaphone), parabolic, hyperbolic, exponential, bi-radial, and tractrix. While some of these designs perform much better than others at overall sound amplification, how the sound is dispersed into the listening area is also important.

  So why am I interested in horns when most of the speakers made today are not horn loaded? It comes down to distortion. A direct radiating speaker makes up for the lack of horn amplification by increasing cone excursion or piston area. The problem with this method is it requires more power to produce the same SPL levels as a horn and causes higher distortion. Every loudspeaker's cone has at least some amount of mass and the farther and faster it has to move, the harder it is to start and stop it precisely.