The Holy Grail of distributed audio; unlimited zones and unlimited sources, cost effectively. That milestone will be achieved, and soon, through the combination of digital amplification and IP based distribution systems. There are systems available today that use one or both of these technologies, such as Oxmoor's Zon system and Netlinks' Netstreams product line. The trend will only continue to grow.

The beauty of this approach is that digital music is data, and, as such, can be distributed easily via an Ethernet network. The traditional concept of zones virtually disappears, as each amplifier on the network gets a unique IP address, enabling an audio stream to be routed to it. When combined with a digital music server, the number of zones is limited only by the ability of the server to serve independent audio streams.

The advent of cost effective digital amplification, produced by companies such as D2 Audio and Flying Mole, allows a small, highly efficient audio amplifier to be located close to the speakers, either in the room or mounted in an electrical box. The logical evolution of this approach is to collocate amplifier with the speaker, creating an active speaker. Additional benefits are realized by incorporating the speaker as part of the circuit. This enables the designer to engineer the speaker and amplifier circuits for optimum performance as a system.

Low powered designs of this nature could take advantage of power over Ethernet (POE), simplifying system wiring by allowing a single CAT-5 cable to be run from the router to the speaker. This would not supply a large amount of power (about 15 watts) due to the constraints of the 24ga conductors used in CAT-5. However, the efficiencies gained by an integrated speaker / amplifier design would mitigate this concern to some degree. This type of system is sufficient for background music applications in many residential environments.

Higher power systems can use the existing speaker wire, in the case of a conventionally wired system, to carry power. It can / does use the existing control cable, since many systems have been wired with CAT-5 to the volume control location, for the data.

The bandwidth of a traditional 10/100 network allow, for all practical purposes, an unlimited number of zones and sources in a residential environment. Partly because of this, Audio Over Ethernet has been used successfully in the commercial audio and sound reinforcement world for a number of years now. Cobranet, from Cirrus Logic is the most popular commercial AOE system used today. Another popular system is available from Digigram. These systems both use the MAC layer of Ethernet and are not actually using IP for transmission.

For both residential and commercial applications another primary advantage of using Ethernet is the ability to use the medium for transporting both audio and control signals down the same wire. This increases flexibility and reduces cost for both installation and material.

As was true in the commercial world, the distribution of audio (and soon, video) and control via Ethernet will continue to proliferate in residential distributed audio applications. The combination of flexibility, cost effectiveness and capability are to attractive to be ignored.