It’s an audio receiver and amplifier integrated into a single component that lets you switch from different sources such as a DVR or Blu-ray Disc player and send the audio/video (AV) signals to multiple speakers and a TV or projector. Though it can be used as a stereo (2- or 2.1 channel) receiver, an HT receiver is meant to output discrete audio channels to at least five speakers plus a subwoofer (the “.1” channel), all external to a TV set’s own, usually inferior, speakers. An HT receiver is sometimes referred to as an AV or surround sound receiver.
In order to reproduce the spatial soundscape created for most HDTV programs, movies on Blu-ray Discs and DVDs and games for computers or gaming consoles, HT receivers are designed to decode the digital audio signal into five full-frequency channels and one low-frequency effects (LFE) channel for distribution to the appropriate speakers. A 5.1 receiver is meant to be wired to three front speakers (left, center and right), two satellites (surround or rear) and a floor-squatting subwoofer. This is the essence of a home theater setup.
The receiver contains outputs for two additional speakers that you position to the side or rear in your home theater for more refined directionality of effects. Alternatively, elevated speakers can be used to literally produce heightened sound. You place them higher than other speakers so that, for example, when a helicopter takes off on the screen, the sound seems to ascend and not just move from front to rear or back. As of the end of 2011, there were some 250 Blu-ray Disc titles available with 7.1 mixes.
The most common is Dolby Digital for 5.1-channel output. But there are variations that the receiver manufacturer might add. For instance, to support 7.1 channels, it may include Dolby Pro Logic IIz or DTS Neo X. Other advanced decoders include Dolby TrueHD and DTS-HD Master Audio. Of course, the program source needs to be compatible. While HDTV programs broadcast by the networks or carried by cable and satellite operators are typically encoded in Dolby Digital 5.1, Blu-ray Discs are most likely to offer a variety of encoding schemes. You use your receiver—set manually or automatically—to select the one that best exploits all your speakers.
Since you’ll likely turn to the best speakers and biggest screen in your home for auditioning any new audio or video device you bring in, a home-theater receiver should be endowed with a large a variety of inputs—some in multiples and some up front. You’ll easily want four or more HDMI inputs to accommodate the latest disc players, cable or satellite receivers/DVRs, media players and game consoles without having to routinely unplug one device just to accommodate another. An HDMI connection supplies both the digital sound and picture. If you have a camcorder with an HDMI output, a temporary connection is facilitated if the receiver has an HDMI input on its front panel. A notebook, ultrabook, netbook or tablet may also have an HDMI output and, again, a front-facing HDMI input is most convenient since such devices aren’t usually left attached to your home theater indefinitely.
If you have a 3D TV, make sure the receiver supports HDMI Version 1.4 or higher for connection of a 3D-capable Blu-ray Disc player, for example. (HDMI v1.4a has 3D pass-through capability, meaning that the receiver neither decodes nor degrades the 3D signal.) Sometimes a receiver is listed as having, say, “7 HD Inputs” with the HD being the abbreviation for “high-definition” video. The number may represent the total of HDMI and component video inputs—the latter being the type that supports an analog video signal but sound must be supplied through a separate audio connection. For digital audio support, you’ll want coaxial and optical connections. It’s good to have a receiver that supports legacy equipment—just make sure it’s not at the expense of plenty of the latest connections.
Only if you never throw anything out. But seriously, to accommodate source devices like VCRs, tape-based camcorders, early HDTV sets and DVD players or even your father’s 27-inch Zenith, you’ll want a receiver with inputs and outputs that predate even component video connections. That means inclusion of such analog connections as composite video, S-Video and stereo audio. Since an HT receiver usually includes an analog radio tuner, there will be RF inputs for attaching the included AM and FM antennas, too.
Some digitally savvy receivers may include a USB port, an Ethernet jack and an iPod dock (or iPod Ready via Optional Dock). The USB port may enable you to play music directly from a flash drive or MP3 player; the Ethernet port may facilitate the streaming of music from a networked computer or network-attached storage device as well as from manufacturer-selected online services such as Pandora or Spotify. An iPod dock speaks for itself, though some receiver manufacturers make the dock an accessory that you attach to a proprietary expansion port. Also, at least one manufacturer offers models that accept an HD Radio tuner accessory that can be plugged into the same proprietary port that otherwise accepts the dock accessory.
The workhorse will be a single HDMI output that you connect to your TV or projector. Secondary outputs include component video and stereo audio. Most outputs on a receiver are dedicated to discrete audio channels wired to your speakers.
It’s always on the front of the receiver (convenient) but almost always sporting a ¼-inch diameter—too large to accommodate the 1/8" (3.5mm) pin tethered to wired headphones or earphones that plug into every portable device. You’ll either need different headphones or an inexpensive adapter (easily misplaced) that converts the jack into one that accepts most of the earphones people carry today.
Because a minority of viewers use the tuner in their TV instead of the tuner(s) in a cable or satellite box, the 5.1 audio signal delivered by broadcasters is demoted to two-channel stereo or simulated surround sound if it stays in the TV set. This is in contrast to a typical home theater setup in which you use a cable- or satellite-compatible DVR for selecting a channel that is then output to your HT receiver, which in turn steers the signals to discrete speakers and the TV. Since using the tuner in the TV would seem to upend the natural order of home-theater components, manufacturers have devised several solutions. The newest is providing a back path along the same HDMI cable that connects your receiver’s output to your TV’s input. When a receiver supports an Audio Return Channel (ARC), you can use a single HDMI connection to transmit digital audio from your TV back to the receiver without needing an additional cable. Without ARC, the TV tuner passes the audio through a digital or stereo output using a dedicated audio cable to a matching input on the receiver. With the newest “smart” TV sets receiving a variety of programming from the Internet—bypassing both the TV’s tuner and an external cable or satellite box—there are more reasons than ever to send an audio signal from the TV to the receiver for output to your home-theater speakers.
The HDMI specification contains something called Consumer Electronic Control (CEC), a technology that enables components in a system to discover and communicate with one another. So, for example, when you turn on a Blu-ray player, the receiver may automatically turn on and switch to the particular HDMI input where the player is connected. This interoperability depends on the manufacturer, and the company may label its CEC implementation with its own name. A manufacturer leverages CEC as a way to sway shoppers to stick with its brand across components.
For the best performance, a minimum of 100 watts per channel (20-20,000 Hz, all channels driven) is recommended. Power is the most misunderstood specification in home theater. For example, a manufacturer might give their receiver a two-channel-driven rating of 100 watts at 20-20,000 Hz. Their five-channel playback (all channels driven) rating might look similar but mean something very different: 100 watts at 1000 Hz, for example. Because it's only given for one frequency, not the entire range, the second spec probably means there is a significant power drop off at the frequency extremes when all five channels are in use. The bottom line is, when looking at power ratings, try to get a rating that covers the full audio spectrum—not just one frequency.
Another factor influences how powerful a receiver you need: whether or not you have a subwoofer with a built-in power amplifier. With a subwoofer in the system, low bass frequencies are filtered from the signals driving the main loudspeakers, which reduce the amount of amplifier power needed to drive them. Low bass requires more amplifier power to reproduce than do midrange and treble frequencies. By directing the bass to the subwoofer and away from the main speakers, the receiver's power amplifiers don't have to work as hard. Adding a powered subwoofer reduces the receiver's power-output requirements by about 20 percent.