Sound System Design

The component that most people associate with a sound system is probably the loudspeaker system as this is what we hear directly. This is only the last part in the chain of a number of different devices that produce, route, process and amplify the signal before it reaches our ear. There are four main parts of a sound system:

1. Input

There are two main types of input device: microphones that convert acoustic sound transmitted via the air into electrical signals that can then be processed and amplified by the system and audio players that convert audio signals encoded on a recording medium into an electrical signal that can then be processed and amplified by the system such as CD and MP3 players.

2. Signal Routing and Processing

The electrical signals derived from the input devices are then fed to a mixer or processor that allows adjustment of level (volume) and tone for each input signal to adjust the sound for the best blend with the other input signals and/or to reduce feedback. Processors are used to manipulate the electronic audio signal in some way, often to add effects and may be built into the mixer or a separate device. Processors are commonly used to increase the intelligibility of the signal and to create as natural a sound as possible.

3. Amplification

The power amplifier amplifies the mixed and processed audio signal to a level that is sufficient to drive the speaker system. These are a vital part of the overall system, handling higher voltage and current than any other component.

4. Output

The last stage in the sound system consists of the loudspeakers that convert the amplified electrical output from the amplifiers back into acoustic sound that we can hear (the reverse of a microphone). The output from the power amplifier is fed to the speaker’s voice coil, where it interacts with the magnetic field surrounding the voice coil to produce corresponding physical motion of the loudspeaker cone.

Sound system design for voice and instrument reinforcement covers wide range of venues from small caf├ęs that hold live events to large scale theatres and concert halls and the requirements for all these different live events are quite different. The sound system must be optimally matched to both the type of event or performance and the size and layout of the venue. Designs for a theatre sound system are completely different to those of a rock venue or conference centre. However, all sound systems are designed to provide a clear, natural (flat) overall sound. If the sound isn’t clear or some frequencies are unnaturally louder or softer than others, the audience will end up fatigued and will not be able to enjoy the event. Achieving clear directionality is also an important part of sound design, the audience should be able to clearly hear the sound coming from the same direction as the performers. The positioning and tuning of the speaker system is critical to achieving clear, natural sound directionality.

The loudspeakers should all be facing in more or less the same direction, and are often clustered together in the centre of the space. Often the primary speakers are not able to provide sufficient sound pressure level or intelligibility throughout the entire auditorium and therefore additional speakers may be positioned to ensure even coverage.