The Digitization of Whole-House Audio

Multi-Source and Multi-Zone Audio is in the Midst of a Sea Change, as it Moves into the Digital Realm
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Multi-Source and Multi-Zone Audio is in the Midst of a Sea Change, as it Moves into the Digital Realm

The steady transition from analog to digital sources and source material, the nascent but growing movement toward digital audio transmission, and the march of networking and the Internet protocol (IP) into the residential market has the once staid and stable field of distributed audio in a bit of a froth.

Until recently, the way that multi-source multi-zone systems are designed has been fairly uniform: multiple analog sources are plugged into a matrix audio switch, having X number of inputs and Y number of outputs. The outputs, which are at analog line level, are fed into a bank of audio power amplifiers. Usually, all of this equipment is located in a central location and speaker wires run from there to speakers located throughout the house. Control has usually been handled via keypads in each room, or a handheld remote, with the control medium typically being infrared (IR) or electrical signalingoften RS-232.

This centralized approach has been the norm since the dawn of audio. However, the increasing use of digital communications techniques means that whole-house audio systems may start adopting more distributed architectures. Indeed, a protocol such as A-BUS has had a distributed architecture for many years, but as audio becomes packetized and sent over networks, it has become easier to implement a distributed system without compromising audio fidelity.

Whether such topology changes are improvements or not is up for debate. To Shay Brummer, president of Interstate Audio & Video in Edmond, Oklahoma, its not about technology or topology. For his firm, product performance, reliability, and ease of installation are key considerations. Multiroom audio is the companys specialty, Brummer said. Its really allowed us to grow our business.

The company has settled on essentially one key vendorELAN Home Systemsfor almost all of its multiroom systems, based on breadth of product line and flexibility. Were able to take ELANs system from an entry level all the way up to one selling in the six figures, Brummer said. We dont have any issues integrating ELANs products with third-party equipment, such as the various source equipment.

Proponents of the digital, distributed systems point to the advantages of getting the power amps closer to the speakers, and shortening speaker cable runs. But those who dont want to take the plunge into digital audio distributionor arent ready just yetsay that the technology isnt mature enough, citing issues such as latency on packet networks, and other audio quality concerns.

One example of the distributed digital approach to whole-house audio is the ZON system, developed by Oxmoor Corp., and distributed through Klipsch Audio Technologies. The ZON system uses keypad-like audio controllers (standouts because of their jog wheel function control and integrated digital stereo amplifier). At the heart of the system is the ZON router, which accepts digital audio streams from up to eight sources and routes them to the various audio controllers, in up to four zones (multiple ZON routers can be cascaded, to add zones).

A distributed architecture comes easily when digital transport is used. Within reason, amplifiers can be a great distance away from the central router device without signal degradation as long as cable lengths are kept within certain prescribed bounds. In fact, the ZON system easily incorporates multiple sources, no matter where they might be; ZON input modules can accept either digital or analog sources. Configured like a single-gang wall plate, the ZON input module takes analog inputs and does a 24-bit analog-to-digital conversion. It then sends the resulting digital audio stream to the ZON router.

Enhanced Category 5 (Cat-5e) or Category 6 cable is used to connect the ZON router to the audio controllers and the input modules. The system can thus leverage a homes structured wiring. This isnt an Ethernet network, however. Oxmoor uses RS-485 to carry data and control signals. (RS-485 is similar to the RS-232 serial data link, but uses differential signaling for improved signal-to-noise ratio, and extended-distance capabilities, as well as higher data transfer rates.)

Putting the power amplifiers in the wall-mounted ZON audio controllers is an interesting approach, but raises questions about heat dissipation and ventilation, as well as how the audio controllers are powered. Oxmoor chairman and CEO Lynn McCroskey said that the Zon Router supplies power across the same Cat-5e cable that carries the audio data and the control signaling.

Twisted-pair network cable might seem like a small-gauge wire to carry much current, but Oxmoor handled that issue in several ways. First, the ZON system delivers power across all of the wires in the cable, rather than just using one or two wire-pairs. This means that the current-carrying demands are spread across more wires, minimizing the current requirements for any one wire. Secondly, Oxmoor uses digital power amplifiers, which the company rates as being more than 90 percent efficient. With that kind of energy savings, the ZAC-60 only requires about 66 watts, while driving the speakers with a total of 60 watts. The wall-mounted ZON audio controllers have an LCD display that gives lots of feedback to the user about the source selections being made.

Another company that takes the distributed digital approach is NetStreams, which has two major lines: Musica, and the flagship, DigiLinX. Musica keypads have digital amplifiers to power the speakers locally, and they use a Cat-5e cable to connect to the Musica Audio Distribution Center. Rather than delivering power to the keypads and power amps across network cables, NetStreams uses the speaker cabling to carry the power. NetStreams cabling recommendationfor either the Musica line or DigiLinXis to run Siamese cable, combining a Cat-5e cable with four conductors of 16-gauge speaker wire, from the head-end or other central location to an appropriate wall location in each room where distributed audio is desired; from there, the cabling then continues on into the room where the speakers are located. The Musica Audio Distribution Centerthe heart of the Musica systemprovides the DC powering to the Musica keypad/power amps and has inputs for up to four analog sources, which it can distribute to as many as six zones. Up to three Audio Distribution Centers can be cascaded, to support up to 18 zones.

NetStreams top-of-the-line DigiLinX system is a fully, end-to-end IP-based distributed audio system with all its audio transport and control handled across a 100BaseT (100 Mbps) Ethernet network running a TCP/IP protocol stack. Touchscreens and keypads control the system, while power amplifier modules, known as SpeakerLinX, power the speakers. In most installations, the SpeakerLinX modules would likely be placed as close as possible to the speakers that they drive to minimize speaker cable lengths and to reduce the attendant resistance losses. Audio sources are brought into the DigiLinX network via MediaLinX modules, which take a digital or analog input and convert it into an uncompressed WAV audio TCP/IP packet stream. DigiLinX uses IP multicasting to efficiently distribute a single stream to multiple devices.

One benefit of a fully IP-based system is that theres virtually no limit to the number of sources or zones, as a 100 Mbps Ethernet switch can support several streams. Another benefit is control. NetStreams has keypads and touchscreens to control the system, but almost anything that can send TCP/IP packets could be used for control, including laptop or desktop computers, Web tablets or PDAs. Connecting a customers home PC LAN to the DigiLinX network is as simple as running a Cat-5e cable from an available port on the PC LANs switch or router to a port on the DigiLinX switch. This would be useful, for example, if the homeowner has music stored on a Microsoft Media Center PC, and wants to be able to stream those files across the network.

A-BUS multi-room audio technology, such as Russounds A-H484 four-source, four-zone hub system, uses keypad controllers that have built-in power amplifiers for the speakers. Cat-5 cables connect keypads to a central A-BUS audio distribution hub. The hub delivers low-voltage DC power to the keypad/power amplifiers across the Cat-5 cable. The fact that A-BUS systems deliver power over Cat-5 cable, while perhaps the systems greatest advantage, is also one of its biggest challenges. Cat-5 cable was developed to carry low-voltage digital signals, and the fairly small wire gauge of the individual wire-pairs used in this type of cable means that they wont handle high levels of electrical current. The power output levels of the distributed amplifiers is thus limited by how much current they can draw (in the case of the Russound keypads, the power amplifiers are rated at 7.5 watts per channel).

As whole-house audio programming material is more likely to be used as background music, rather than for focused, critical listening, the power limitation, in fact, may not be much of an issue. Still, those designing and installing A-BUS systems will want to pay attention to sensitivity specifications when selecting speakers, as every dB gained through speaker sensitivity is a dB that doesnt have to be bought with amplifier power. Filling exceptionally large rooms with high-volume sound would be yet another challenge for these types of systems.
Although the A-BUS system is distributed in architecture, the rest of Russounds product line is centralized. Russounds CA range is the next step up from the A-BUS system, with the CAS44 four-source, four-zone controller and the CAA66, which handles six sources, serving up to six zones. Both of these systems have built-in power amplifiers, delivering 20 watts RMS per channel.

Rather than go for a distributed topology, Niles Audios multirooom audio products continue to use analog transport and a centralized topology. For Niles, the big trend has been the proliferation of digital audio sources, such as media servers, satellite radio, and Apple Computers iPod.

These types of sources make it necessary to deal with not just the audio stream, but metadata (source name, frequency of the radio station being tuned to, name of band or performer, title of song being played) as well, said Keith Kennedy, director of product management for Niles.

At the recent CEDIA EXPO, Niles introduced its newest multi-source, multi-zone audio system, the IntelliControl ICS. Expected to begin shipping in the first quarter of 2006, the product line is centered around the IntelliControl ICS GXR2 receiver, which is a six-source, six-zone modular receiver with a media bay. Niles plans to offer a full suite of source modules, including an AM/FM tuner module, an XM satellite radio module, a Sirius satellite radio module, and an iPod interface module. There will also be an audio input module, to bring audio from CD players, DVD players, cable TV or satellite TV set-top boxes into the system. The GXR2 receiver delivers 60 watts RMS per channel into six stereo zones. Multiple GXR2s can be linked together to create a distributed audio system covering up to 30 zones.

With the system, Niles will offer a range of controls, from keypads to a color in-wall touchscreen. In addition, a new handheld remote, known as the iRemote, will use Zigbee radio technologya newly emerging wireless standard targeted at a variety of automation and control applicationsto communicate with the rest of the IntelliControl ICS system. The iRemote sports all of the controls needed to operate the various sources, as well as a display that gives the user feedback about source selections and shows any metadata associated with the music being played or the current station.

Lee Travis, CEO of Home Technologies, in Bellevue, Washington, says that multiroom audio is one of the more stable chemicals in our mix of products that are changing all the time. Like Brummer, Travis doesnt find the question of distributed versus centralized architectures to be important. The bigger issue is controland getting feedback fromthe audio sources.

When asked if there was anything in the way of distributed audio systems that he wished were different, Travis cited infrared emitters as sometimes being an annoyance. People cleaning equipment can easily knock them off the components, and they can sometimes malfunction. The next phase of controlling all these devicesand its a surprise to me that its not here yetis that they will all be IP addressable and Ethernet enabled; thats the most logical way to control these sources, and get feedback to the user.

Tim Corder, president of Hods Home Theater (Waterford, Michigan), says that the biggest differentiation point for us, among the various systems weve dealt with, is the level of feedback that the customer gets, as theyre using the system. In years past, Corder observes, there was a wide chasm between entry-level distributed audio systems, which he positioned as selling for a few hundred dollars per room, and the Crestrons and AMXs of the world, which were $3,000 per room. The result, he said, was that the user experiences for those two polar opposites were radically different.

Corder sees the user interface amenities that were typically the domain of the high-end systems moving down to more attractive price points. Hes particularly looking forward to the availability of Crestrons newly announced Adagio whole-house audio line, which targets a more modest price point than Crestrons previous and current higher-end solutions.

That Crestron is already a key supplier for his company, and that Adagio can tightly integrate with Crestrons other control capabilities hold a lot of appeal for Corder. Unlike most multiroom audio systems, which usually have the look of a basic metal box, and are typically expected to be hidden away in an equipment room somewhere, Crestrons new Adagio line comprises several products that are styled like audio components. The Adagio Audio Distribution system (AADS) is a six-source, six-zone multi-room receiver with 12 channels of power amplification (45 watts per channel), an AM/FM tuner, and a XM satellite radio tuner. The AADS can be expanded to support 12 zones by adding an Adagio Audio Expander (AAE). By using multiple AAEs (up to three), as many as 24 zones can be served.

The Adagio Entertainment System (AES) is similar to the AADS, but instead of the built-in AM/FM and XM tuners of the AADS, up to three optional radio tuner cards can be installed. These cards consist of a dual AM/FM tuner card, an AM/FM tuner plus XM tuner card, and an AM/FM tuner plus Sirius satellite radio tuner card.

As befits audio components, both the AADS and AES can be controlled from the front panel, as well as by a number of Crestron keypads and touch panels. Crestron also offers several audio source products, including the Adagio Audio Server (AAS) and the Apple iPod Connect iPod dock.

Clear Communications Needed. Joe Arceo, manager of the A/V division at NuSystems Inc. in Gardnerville, Nevada, cautions that we need to take the time to really understand what it is that our customers are looking for. Some are perfectly happy with a single-zone system, while others really do need multiple zones. A lot of clients dont necessarily know exactly what we mean when we use terms like multi-source, or multi-zone, he said. In other words, its important to speak with clients in language that they understand.

We use a lot of SpeakerCraft systems, Arceo said, citing SpeakerCrafts MZC-66 multi-zone controller as one that they frequently use for multi-room audio systems. They can program the SpeakerCraft keypads to do some automation, and the keypads have IR receivers built in. So were taking command codes and programming them into a handheld remote (from Universal Remote Control). With that remote, the user can change channels, volume, etc., right from the remote, and the keypad relays the IR commands back to the source devices.

For situations where users need more feedback from source devices, Arceo said, Were typically putting in an AMX touchpanel system.

AMX bases its audio distribution solution around its MAX Media Server, which is capable of simultaneously serving up as many as 25 audio or audio/video streams per server. (The MAX handles video as well as audio media.) The MAX connects via Universal Serial Bus (USB) to AMXs Audio Only Module, which has four analog stereo line-level outputs. These outputs can be fed to power amplifiers, to drive the speakers. A pair of Audio Only Modules could be used to serve eight zones.

The aforementioned SpeakerCraft MZC-66 Multi-Zone Controller is a six-source, six-zone system incorporating built-in power amplifiers providing 12 channels of amplification, with 30 Watts per channel. SpeakerCraft expects to soon be shipping its MZC-88, which will offer more power (50 watts per channel into 16 channels), and the ability to handle more sources and more zones (eight sources, and eight zones). Two of those sources can come from the two built-in AM/FM tuners. Bill Cawlfield, VP of SpeakerCrafts electronics group, noted that both of these systems utilize digital power amplifiers, which dissipate significantly less heat than their analog brethren. This enabled the company to pack a large number of power amplifiers into one box, without running into thermal problems. SpeakerCraft also offers an MZC/iPod Interface kit.

With home networks, the structured wiring concept dictates that cabling be home runned; each Cat-5 (or Cat-5e, or Cat-6) cable is run from the RJ-45 wall jack in the room that it serves, to some central point in the home, where it terminates on a patch panel, usually mounted in some type of structured wiring enclosure. When wiring a home for distributed audio, much the same approach is followed, with speaker wires and Cat-5 cables converging on some central pointbut just where should that point be? According to Scott Sylvester, director of product strategy for Sonance, In most systems, somebodys home theaterwhich has all the sources connected to itis in fact the unifying point to which one of our multiroom audio boxes connects. A simple connection to that home theater lets you get audio signals and even video signals from it.

The Sonance product has traditionally been designed as a premium brand, Sylvester noted. We have amplifiers that will handle long distances, and drive low impedance loads, and we tend to use nothing but discrete components, so the sound quality level is high.

Sonances DAB1 Distributed Audio System is a four-source, six-zone distributed audio system. It includes a built-in AM/FM tuner. Amplifier power is 30 watts per channel. The DAB1 also includes a handheld IR remote. On the source side, Sonance offers the iPort, the docking station and interface for Apples iPod.

Although several companies are coming out with distributed, digital multi-room audio systems, theres as yet no consensus that this is the only way to go. System performance, reliability, a powerful yet intuitive user interface, technical support, programming and integration support remain key considerations for dealers and their clients.

Theres certainly consensus about the explosion of new audio sourcesmost of them digital, and many of them able to report their status and deliver metadata to the user. This raises the requirement to support a large number of sources, and to integrate tightly with an expanding range of sources. It has caused most manufacturers to re-think their user interface at the keypad/touchscreen, and also resulted in a flood of Apple iPod docking stations and interfaces.

Media servers are looming large as one of the key sources for multi-room audio. That being the case, one consideration for multi-source, multi-zone systems is the number of audio streams that the media server can simultaneously deliver.

A former loudspeaker designer, Alan R. Frank ( is a freelance writer and networking consultant.