Home audio and video isn't as simple as flipping on the TV and cranking up the Hi-Fi anymore. Interconnection is adding a new dimension to entertaining technology.
Whole-house audio and video (A/V) systems are becoming more popular with many homeowners today because of their ability to centralize television and stereo equipment. As a home technology integrator (HTI), your goal is to provide the homeowner with the best hardware choices currently available and the ability to easily upgrade in the future. This third article in a series of 12 on home integration will address A/V system installations as part of the whole-house technology solution.
A whole-house audio system is designed to distribute audio signals from a central media room to the rest of the house, allowing the homeowner to turn components on and off or adjust the volume with a series of controls from any room in the house.
The residential structured cabling for an audio system described below should be wired in three runs:
Amplifier locations to the distribution device (DD)
Wiring in new construction that connects the amplifier and/or source equipment location to the DD should include six speaker wire conductors and one Cat. 5e cable. Four of the conductors feed audio signals to the DD, and the other two deliver low-voltage DC current to the DD for switching and control purposes. The Cat. 5e cable supports infrared remote controls and data communications.
DD location to the volume control locations
Each volume control should be connected to the DD using four speaker wire conductors and one Cat. 5e cable.
Volume control locations to the speakers
Each speaker should be connected to its associated volume control with a minimum of two speaker wire conductors. Cat. 5e cable will make possible future upgrades like the installation of amplified speakers and IR applications.
A single-source system distributes the same audio signal to all zones in the home, and a single amplifier drives all the speakers in the house (Fig. 1). Although simple in design, the single-source system is limited in functionality — some form of whole-house control system is necessary for making adjustments to source equipment. By contrast, a multi-source system will allow users located in different rooms of the house to select a different audio signal (Fig. 2).
As in whole-house audio distribution, the distribution device is the center of the design for whole-house video distribution. These systems use dual-connector coaxial wall plates in each room of the house to allow the homeowner to view any cable/antenna/satellite channel, as well as any video camera, VCR, or DVD player signal on any television in the house.
Several remote access systems are available for controlling whole-house A/V systems, including infrared-repeater and RF control systems, and infrared learning keypads. Most are usually dial-up or Web-based. Web access is possible with a browser and Internet protocol (IP) that uses a browser-based personalized control portal.
Externally provided services.
But how do these signals get into the home in the first place? Television programs and music enter the house via antenna, satellite dish, or coaxial cable. The delivery system is an important consideration that you and the customer must agree upon early in the design process.
Cable television is available in most regions of the country, and the number and type of services provided by cable companies continues to grow. In addition to basic programming, many cable television companies now offer digital cable and high-speed Internet access.
To receive a cable television signal in the home, homeowners need one of the following pieces of equipment:
Converters, or set-top boxes, are required when the homeowner doesn't have a cable-ready television. All televisions require a converter for digital programming.
Cable-ready TVs receive outside television signals and display them using an internal receiver/tuner that operates much like a set-top box.
Satellite dishes are necessary for capturing digital broadcast satellite (DBS) signals. DBS provides digital-quality pictures, but a different receiver is necessary for each television in the home for independent viewing on each TV.
Audio signals are transmitted in analog or digital form. Until recently, broadcast and telephone transmissions have used analog signals. The advent of digital audio has produced greatly improved sound and is becoming the preferred method for receiving music and other audio files.
Analog signals are amplified to add information to the signal. On the other hand, digital signals are discontinuous and change from one state to another in a limited number of discrete steps or voltage levels. A simple digital audio signal will have two states or signal levels — ON translates to digit 1, and OFF corresponds to digit 0. Both levels can also be represented as a positive or negative voltage.
Internet music, radio, and movies are common examples of external services shared throughout the home via the A/V components of a residential network.
An A/V system can be divided into two groups: the distribution equipment and source equipment.
Distribution equipment, as its name implies, distributes the A/V signal throughout the home to various source devices. A central receiver is the common distributor for an A/V system. Audio and video images from various source devices within the home are modulated, or put in various channels, and sent to the distribution device, which then makes the signal available to all rooms in the house. If the signal is to travel from room to room, it's a good idea to install an amplifier to boost the signal back to the required threshold. In whole-house audio systems, be sure to use multi-zone amplifiers.
Also note that if you connect a television to an outlet located too close to the amplifier, it may receive signals stronger than the threshold for normal functionality. If this is the case, you may have to install an attenuator to reduce the signal strength to a tolerable limit.
Source devices like security/surveillance cameras, DVDs, VCRs, and CD players produce audio/video signals that need to be modulated and amplified.
Speakers are electromechanical devices that convert electronic audio signals to sound. The following criteria will determine which speakers the system will need:
Dispersion — The even dispersal of sound is an important design element for whole-house A/V systems. Make sure the speakers you select give the customer maximum stereo sound coverage throughout the entire home.
Room size and sensitivity — Balance is key to sound quality. You may need to install additional speakers in larger areas to provide better coverage and balanced sound levels.
Aesthetics — You should select speakers to fit the décor of the room, taking into account color and shape.
In a multi-speaker stereo zone, try to locate the speakers equidistant from each other and away from the room corners or boundaries. Placing the speakers too close to a room boundary could cause an undesired booming effect.
Low-voltage wiring transmits signals using small or, in some cases, trace voltages for data transmission. The details for a standards-compliant audio cabling system are specified in ANSI/TIA/EIA-570-A-3. A typical A/V cabling system design will use the following cables:
75-ohm coaxial Series 6 (RG-6) cables are used for transmitting A/V signals.
Shielded twisted-pair (STP) wiring is used for balanced analog and digital audio signals in professional audio systems.
Shielded single-wire cables are similar in construction to coax and used for unbalanced analog audio signals in consumer audio systems.
14- or 16-gauge speaker wire is used for wiring audio speakers.
Unshielded twisted-pair (UTP) wiring is used in some A/V system installations for transporting certain control signals where Cat. 5 cable is needed.
Speaker wire should be run in pairs to each speaker and terminated in one of two ways. For stand-alone speakers, terminate the ends of the speaker wire to a speaker-connector wall plate — a banana jack or five-way binding post type connector is preferable. For in-wall speakers, terminate the ends of the speaker wires directly to each speaker.
Several types of video connections are available, and each has its own effect on picture quality. A sample of options is listed here in order of video quality, from worst to best:
Composite cable uses a single RCA connector to combine the black-and-white and color parts of the video signal.
F (or RF) cable uses an F-type connector commonly used in cable television installations. If you don't make additional connections for a separate audio signal, only a mono audio signal will be received.
A/V jacks are equipped with three RCA connectors: yellow for video, red for the right channel, and white for the left channel.
Super-video (S-video) cable uses a round multi-pin connector.
You can also use wireless connections for A/V and home entertainment subsystems. You can distribute the signals around the home without the use of any wires by using RF technology. Wireless speakers receive signals from the wireless line/level distribution system.
The most important aspect of a wireless video solution is the frequency spectrum on which the signals are distributed. The higher the frequency, the more effectively they'll be able to pass through physical obstacles like walls, ceilings, and floors.
Connecting A/V components.
Now that you've got the A/V infrastructure in place, it's time to interconnect the devices. To install A/V components, start at the source devices and run wire from the distribution devices to the speakers. Connect devices to the control amplifier first, and then connect the source devices to the receiver. Next, connect the A/V output interfaces of the receiver to a connecting block or speaker selector device. In each room, terminate the speaker wire and connect the volume control device to the speakers. You'll also need to connect the antenna components. Be careful to install the antennas away from outdoor power conductors to minimize interference, and be sure to securely attach the lead-in wires to the antenna.
Simply connecting A/V devices together in a home network doesn't guarantee that the devices will communicate with each other. They need to share some sort of commonly understood language or protocol that will instruct them on when and how to transmit signals across the network. The two most popular protocols in use today are Home Audio/Video Interoperability and the Digital Harmony suite.
Troubleshooting and testing.
A critical part of any installation is troubleshooting and testing the system. For terminated audio cable, check to see that the resistance (impedance) reading of the cable from the audio module in the distribution device is close to that of the terminals on the volume control or speaker to which the audio cable run is terminated. A measurement close to the resistance of the volume control or speaker indicates the cable is continuous and without shorts.
Look for damaged speaker cable runs and perform a standard continuity test. Check all connections for loose strands and make sure the terminal screws are secure. Once all audio module connections, volume control connections, and speaker connections are complete, turn the system on. Turn the volume all the way down and then slowly raise it to test overall system performance. Always remember to test the speakers before connecting the amplifiers to avoid accidental damage to the amps.
The easiest way to perform basic testing is to use a multimeter or volt-ohmmeter to test for shorts and continuity. Perform both tests on the length of cable from the distribution device to a junction box or wall outlet. Cables shouldn't be longer than 275 ft. Once you've tested the system and it's operating correctly, document all connectivity, equipment layout, device locations, and any final adjustments you've made. Finish up by performing a walk-through with the customer. Go over all warranty and operation material to ensure that the customer will be able to get the most from the system.
Dusthimer is publisher of Cisco Learning Institute Press, York, Pa.
Sidebar: The Next Generation of TVs
Flat-panel displays or plasma screens represent the latest in television technology. They offer better picture quality, take up less space than traditional televisions, and can be hung on a wall like a painting. Their resolution meets the high-definition (HDTV) standards with an aspect ratio of 16:9.
Sidebar: Beyond the VCR
One of the newest products on the market for digital television is the personal video recorder (PVR). TiVo and Replay Networks (maker of ReplayTV) were the first companies to release the first generation of PVRs. A PVR records, plays, and pauses TV shows and movies. It uses a large hard disk along with sophisticated video compression and decompression hardware to record television streaming.
To put it another way, a PVR is a stripped-down PC with a large hard disk that reserves storage space for downloading program listings every day. You use a remote control to select what you want to record and the PVR captures and stores these programs on the hard disk for future viewing.