Understanding the Basics of Distributed Audio Systems



Barry Manilow gently sings “Copacabana” in the background as you pick up a jar of mayonnaise, when suddenly the jar slips from your fingertips and crashes to the supermarket floor. An announcement blares over the soft music: “We need someone to clean up Aisle Nine!” Then Mr. Manilow’s music gently swells back up.

Restaurants, fitness centers, office buildings and many other businesses rely on a specific kind of sound system. These systems are referred to as "distributed audio systems." Other names are used to refer to these systems as well, including “70-Volt Systems” and “Constant Power Systems.”

What truly differentiates a distributed audio system from a standard PA system is that transformers are built into the speakers and special amplifiers are used to power the speakers properly. The speakers’ onboard electronics distribute the power from the amplifier evenly and safely. This enables many speakers to be chained together in parallel, which in turn enables hotel staff to announce that “Elvis… has left the building.”

Distributed audio systems can be as small or large as you need them to be. You can install your own system if you’re comfortable with basic speaker wiring techniques. It’s important to pay attention to details. You must make sure the power rating of your chosen amplifier can safely run the speakers in your system.

Larger-scale systems often require more involved wiring schemes and heavy-duty construction. Professional contractors are sometimes required for those types of installations.

Distributed audio systems must be designed to suit individual needs. In order to determine what equipment will be necessary to create a system, you must first determine the requirements of the installation. Is the system being used only to project someone’s voice throughout a quiet building, or will you need a more powerful system that can page and provide background music at a noisy bar?

There are three basic types of distributed audio systems:

  1. Background
  2. Foreground
  3. A combination of the two

Quiet office buildings and recreation centers generally require soft background music, with the ability to page. This is an example of a background system. Nightclubs, performance venues and loud restaurants need the ability to turn up the volume, and thus require a foreground system. Basically, a background system is restricted to only providing low volume levels. A foreground system has the ability to provide louder volumes.

Health clubs commonly require loud background music in the treadmill area, quiet ambient music in the yoga room and perhaps even promotional material looping in the reception area. They also need the ability to page members and trainers throughout the gym. This is an example of having the need for a combination of the two types of systems.

Two types of speakers are used for fixed installations:

  1. Ceiling-Mount Speakers (internal)
  2. Surface-Mount Speakers (external)

Surface-Mount speakers usually offer better sound quality for music and are easier to install. Ceiling-Mount speakers are hidden away inside of ceilings and walls and offer a better choice for visually non-invasive, aesthetically-minded customers. Structural limitations must be taken into consideration when designing a distributed audio system. Varying construction materials such as drop ceilings, concrete walls and high rafters will affect your speaker options, mounting options and the sonic characteristics of the space.

Once the proper speakers are chosen, a "distributed amplifier" will be needed. Depending on the number of speakers in use, and the overall power requirements of those speakers, multiple amplifiers or a multi-channel amplifier may be necessary. If you want to have different audio playing in different zones, like the fitness club described earlier, you’re going to need an amplifier with multiple zone controls.

Next you must consider what sound sources will be needed. These sound sources may include microphones, a CD player, an MP3 player, radio, satellite radio, the audio output from a DVD player, cassette players, etc. More often than not, an installation will require mixing more than one of these sound sources. This is why a mixer is required. B&H sells both stand-alone distributed audio mixers as well as mixers that are integrated into the distributed amplifier in a single unit. B&H also sells distributed audio mixers with CD players, MP3 players, etc. built into them.

Other possibilities to consider are options such as remotely positioned volume controls. This way a yoga instructor can turn down the volume and a Jazzercise instructor can crank it up. There is equipment available that gives you the option of installing a wall-mounted volume control that also features a microphone input and a button to select the proper audio for the room. There are many different components available to customize a system that could give your business a creative edge.

Another option to consider is the use of a "ducker." In the professional audio world, a ducker is not something you feed breadcrumbs in the park. A ducker allows your voice to be louder than the background music when you make an announcement, like when you dropped that jar of mayonnaise and the check-out clerk’s voice momentarily overpowered Barry Manilow. Interfacing your telephone or fire alarm into the distributed audio system are also possibilities.

If you’re planning on installing a system, it’s important to familiarize yourself with the process of matching amplifiers with speakers. There are more resources about this topic available at the websites of some of the manufacturers that B&H carries, such as Atlas, Bogen and JBL. The majority of larger-scale systems are designed by experienced professionals. A qualified contractor needs to be familiar with all of the options available and all the pitfalls to avoid. In both cases, proper system design will serve all of your organization’s needs and let you concentrate on more important matters, like cleaning up Aisle Nine.

Have any questions about distributed audio systems? Please post them in the Comments section below.




A "wall-mounted volume control that also features a microphone input " was mentioned but I can't seem to find that here. Could you recommend some specific models that do this? Basically, I am peicing together a 70v system for a small multi floor church, and it would be great to add microphone input for some rooms but not for the entire system

By microphone input for indivual rooms, I mean having the mic only heard in the room it's in, not heard across the rest of the 70v system

Hello -

Currently we do not offer a wall plate that combines a volume control and a microphone input.  They are available as separate componets only: 

Astatic 40-347 Single 3-Pin XLR Female Wall Plate   and  Bogen Communications SLC Signal Level Control