Understanding Live Sound

Live sound applies to both the musician and the DJ. The first thing you need to learn about sound is sound itself. What is sound? Sound is nothing more than waves of changing air pressure that cause your eardrums to move. Sound starts with a physical resonant source this could be your vocal cords, a speaker or anything else that makes sound. This vibration causes air to move. And when this moving air hits your eardrum, your eardrum will resonate in proportion with the source. This is the essence of sound. It takes all three ingredients; a source, a medium to pass it through and something to receive it. OK now let's talk about dispersion. Dispersion is the direction that sound will go, after it has left the source. You'll usually hear the term dispersion in reference to live PA speakers. You know, 90X60, 60X40 and so on. Once sound leaves a piezo or compression driver it needs to be controlled. A horn attached to a driver will do just that. At the base of the horn, is the throat. The throat is a narrow channel that the sound squeezes through. Once the sound leaves the throat, it wants to explosively spread out in all directions. Now it's up to the horn flare to control the angles of dispersion. Some horn designs are better than others though. If you have a 90X60 horn, you would expect that all the frequencies would be dispersed in this pattern. This is not always the case. The best horn designs that we deal with are waveguides and constant directivity or CD horns. These are both designed to disperse all audible frequencies in the specified angles. Waveguides look like round dishes and naturally, they give a cone shaped dispersion. CD horns are what you see in most PA cabinets today. They offer a more horizontal dispersion. www.musicanddjinstructionalmedia.com