What is the difference between direct radiation and horn loading?
With direct radiation, a vibratory element (such as a cone loudspeaker) radiates directly into the air. Horn loading takes place when the loudspeaker couples with air through a horn. In doing that greater efficiency is achieved, that is, more sound and less heat. We also get more directionality. The theoretical size for a horn is inversely proportional to frequency. That is why, for bass bins, the horn of which would be impracticably large, the horn has to be “folded” inside the box, thus referred to as a “folded horn” box.