I'm going to use the next couple of blogs to review what happens to sound from its origin onstage to the final audible sound that emerges from the house speakers and is heard by the audience. For the purpose of the exercise, let's assume we are working with a nine-piece show band on a large stage in a hotel or conference center ballroom.
Here is what a typical stage plot for the band might look like when they (the band) give it to the event manager who forwards it to the audio company.
As you can see, there are quite a few extra pieces of equipment which have been added to what started as a simple request from the band. Let's look at what these are, but more importantly, why they are needed to convert the band's sound to one that can be heard by the entire audience. We'll do it by following what we call the audio signal.
First of all, the audio signal begins as a sound wave within the INPUT GROUP of equipment, most of which is generally found onstage. This group of equipment includes vocal and instrument microphones, which convert sound waves like a vocalist's voice into tiny electrical signals. Other members of this group include instrument DIs (direct input boxes), keyboard mixers, and occasionally CD/DVD players controlled by performers.
Second, the audio signal (now comprised of small electrical signals) goes into a transformer-isolated "snake" that sends one set of the same signals to the main mixer, and one set to the monitor mixer. The snake is really just a long "extension cord" that connects all the signals onstage to the equipment the audio engineer uses at the audio control position at Front-Of-House (FOH), usually at least 30 ft across the room. It also connects the onstage signals with the monitor engineer position near the stage. He/she is the person who controls the sound the musicians use to hear themselves because they cannot hear the main room speakers onstage since they (the musicians) are physically behind the main speakers.
Third, the audio signal is processed in the SIGNAL PROCESSING AND ROUTING GROUP, by the main house (FOH) mixer, located at that position typically 30 ft or more across the room from the stage, where it is raised in strength, and has various effects like reverb added in the house effects racks, then is looped back to the main mixer.
Fourth and last, the audio signal goes from the main mixer into the OUTPUT GROUP, in which a house equalizer adjusts frequencies, a house limiter controls the maximum strength of the signal, house crossovers split it into different frequency bands, power amplifiers boost its strength, and finally the house speakers which convert it back into sound waves that the audience hears.
That's a very brief and simple overview and no doubt some of the terminology is still confusing although you have probably heard the terms before. In my next post, I will review what is entailed in a sound check and what the audio engineer does during an event, as well as trying to explain in a little more detail what the purpose of all this equipment is.