Distributed Audio Systems

If you have even been to a shopping mall, there is a good chance you have heard music or an announcement coming through a loudspeaker system. These loudspeaker systems are known as distributed audio systems.

A distributed audio system, as its name implies, distributes audio to many loudspeakers at the same time instead of only one or a few loudspeakers. Other common names associated with these systems are 70-V System and Constant Power System. In a distributed audio system, transformers (typically 70V but higher or lower voltage transformers are not uncommon) are needed and amplifiers are used to power the loudspeaker appropriately. Transformers are needed both at the origin of the sound source and at the end point, or loudspeakers. At the origin of the sound source, the transformers employed are called “step up” transformers which allows a high voltage/low current signal to travel through the connecting wires. Each loudspeaker has its own “step down” transformer to convert the signal back to the desired voltage level. By employing transformers, it becomes possible to transmit signals over long distances without significant line losses, while at the same time the size of cables can be kept relatively small.

Distributed audio systems can fall into three categories, background, foreground or a combination of the two. In a foreground application, the sound is usually loud while in background systems the sound is usually quieter. In certain applications, both background and foreground are needed, like a shopping mall where the music is generally soft (background) but at times it may become necessary for an announcement to be made which would need to be louder than the soft music.

There are distinct benefits to using a distributed audio system such as:

-Smaller size cables can be used to connect speakers to the amplifier.

-Cables can be longer with negligible line loss.

-Loudspeakers can be added to the system as they are needed.

-One amplifier can control many loudspeakers.

-Volume control of individual loudspeaker is possible independent of the master volume control.

The biggest disadvantage of a distributed audio system is the use of the transformer; it adds cost.

The speakers in distributed audio systems can be either ceiling mount or surface (wall) mount.

Stetron specializes in designing loudspeaker drivers for use in distributed audio systems. Contact us for your next audio project.