Setting Up an Audio System in a Media Room or Home Theater
The basic building blocks of any entertainment system are sound, sources and displays. For most media rooms, the sound or audio system is a combination of an audio-video (AV) receiver plus five or more loudspeakers and a subwoofer.
The heart of the AV system is the receiver. Today's receivers perform many functions:
They power the loudspeakers; the speaker wires are connected to the back of the receiver.
All of the sources (cable box or satellite, DVD, game system, etc.) are connected to the receiver, which lets you select which source you want to hear.
The AV receiver lets you control the volume and adjust the balance between the loudspeakers.
The receiver also sends the video signal to the television or monitor.
The receiver processes the audio, including the information for surround-sound effects. On some newer receivers, it also performs video conversion.
Many better televisions also have audio amplifiers, connections for multiple sources and surround processing, but for most applications it is better to use a separate audio video receiver. The receiver will almost always have more power and flexibility.
The receiver contains five or more audio amplifiers, which power the main loudspeakers. Most subwoofers have their own amplifiers. It's easy get wrapped up with the wattage rating for a receiver, but keep in mind that all watts are not created equally. There are many different ways of measuring the wattage output of an audio amplifier; lower-quality amplifiers are often rated at a smaller frequency range. So it's a good idea to stay with quality brand names and look for a power rating that covers the full range of human hearing: 20Hz to 20kHz.
The loudspeakers in a typical media-room system include:
- A center channel loudspeaker, which is the most important loudspeaker. Virtually all of the dialogue is sent to the center channel. Don't skimp here; a low-quality speaker will make it difficult to understand the actors in your favorite movie. The center channel speaker should be placed as close as possible to the television. It is usually mounted directly above or below the screen.
- A left front and right front loudspeaker, which should be identical and placed an equal distance to the left and right of the television.
- At least two rear surround sound speakers to give the sound a three-dimensional effect. They should be placed above and slightly behind the main seating area. How much sound comes from these speakers depends on what the sound engineer producing the program wants. In many movies that are mostly dialogue, the rear speakers might never be used, while in an action adventure movie, they could be utilized during the majority of the film. Sound coming from the back can be as dramatic as an airplane flying overhead, or a car approaching from the rear in a chase scene, or as subtle as background noise in a restaurant.
- A subwoofer can be placed almost anywhere in the room. Humans can't identify the direction from which a bass sound comes --a phenomenon that makes it very convenient for placing the subwoofer in home theaters and media rooms. Usually the largest of all of the loudspeakers in a surround-sound system, the subwoofer can be placed where it is partially or totally concealed. In some loudspeaker systems, the woofers for the bass are in the main left and right loudspeakers.
- For more on speaker placement, check out the section on room layout at the Dolby website.
Some of the most common questions I get are about Dolby Digital and DTS surround systems, often defined by numbers such as 5.1. With such systems, the number 5 specifies the number of main speakers that can be used; the 1 indicates that a subwoofer can be connected. Later versions of surround-sound processing allow for six or seven main loudspeakers; they are labeled 6.1, 7.1, etc.
Dolby Digital and DTS (digital theater system) are the main surround-sound processing systems. Most audio video receivers are capable of decoding either one.