Monday, September 14, 2015

How to Buy an AV Receiver






Oh boy, the times, they are a changin’. With the explosion of integrated soundbar offerings—including some pretentious premium models—it would be easy to dismiss the audio/video receiver, once the great ruler of the home theater world, as an aging relic. Enthusiasts know better.Sure, AVRs are more complicated to hook up than an all-in-one soundbar, and receiver-based systems virtually scream for a universal remote (or at least a kick-ass control app) to ease day-to-day operation. You need to run all those cables, too. But what you get in return for spreading out your (carefully selected) speakers and installing a bona fide, hard-core audio amplifier at the heart of your system can be summed up in one word: performance. It all comes out as improved dynamics (the ability to react to sudden peaks in the audio program), a more realistic soundstage (sounds appearing in distinct locations), and greater detail (especially at loud volume) than you’re likely to hear from any soundbar or small, powered speaker system. Factor in Dolby Atmos and DTS:X, the new object-based surround formats that are so far only available in receivers and separate surround processors, and you’ve got a compelling argument for sticking with the tried and true AVR.

All-in-One Fun

An AV receiver combines two separate audio components in one box: a preamplifier/surround processor (often called a pre/pro) and a power amplifier. The pre/pro is where audio and video switching occurs, allowing you to connect multiple sources to the same AVR and select each with the push of a button. Once selected, your source components (a cable box, Blu-ray player, smart TV, or even your smartphone) deliver a low-level audio signal to the unit’s preamp section, where it can be manipulated for volume or tone (equalization) adjustments and surround decoding before being sent to the AVR’s power amp section.
The surround processor section decodes the multichannel digital audio bitstream signals from discs, broadcasts, or Internet video streams—say a Dolby Digital or DTS soundtrack—and directs the appropriate sound to each speaker. Matrix-surround signals encoded onto stereo analog tracks will also be decoded here. Alternately, the surround processor can take a two-channel stereo track and derive a form of surround sound from that, utilizing all the additional speakers in the system. Once all that’s done, the power amplifier simply provides gain to pump up the signal level and drive your speakers to sufficient (if not earth-moving) volume.




How Many Speakers?

We remain committed to the idea that the basic 5.1-channel configuration is sufficient for an engaging home theater experience. This includes front left-, front center-, and front right-channel speakers; a pair of surround speakers placed ideally along the side walls (and slightly behind the prime seats); and a dedicated powered subwoofer (the .1). Blu-ray Discs and streamed movies that carry discrete high-resolution 7.1-channel soundtracks have become more common in recent years, which helps justify adding back-wall surrounds, but any extra speakers beyond 5.1 channels are an enhancement, not a requirement. If your AVR comes with extra channels, they can often be configured to drive a pair of speakers in another room, usually referred to as Zone 2.
Until the introduction of Dolby Atmos for the home, the only way to make use of a nine- or even 11-channel AVR (besides running extra zones) was with processing that artificially derives information for additional front-wall-mounted height or width speakers. With no discrete soundtracks available, the value of adding those extra speakers and amplifiers remained dubious. But object-based surround sound, which provides discrete information to two, four, or even more ceiling-mounted speakers (or the equivalent), changes that equation. See “Surround Modes,” below, for more on object-based surround.

Much Power?

Amplifier power is a critical spec for any AVR, but it’s difficult to shop by the numbers. Any receiver priced over $500 today is likely spec’d at or near 100 watts per channel, each with an appropriate 0.1 percent total harmonic distortion measurement (at least, with only one channel running at a time). So what’s the difference between one similarly rated amp and another? The answer, more or less, is what we call “headroom.” A great amp with power supply capacity to spare will rise to the occasion on loud, complex passages on multiple channels without introducing audible distortion. Other AVRs will sound coarse, or run out of steam and clamp down on power output to all the channels (or even shut down temporarily) to avoid overheating.
A telling sign is the five- and seven- channels-driven test bench measurements Sound & Vision includes with AVR reviews. Although this torture test is far more demanding than any real-world situation an AVR is likely to encounter, power output that meets or approaches the published two-channel specification with five or seven channels working all out simultaneously usually indicates a more robust power supply and the ability to drive your system to louder levels with less strain. Keep in mind, though, that the amp that achieves this isn’t always the biggest or heaviest. Newer circuit topologies—notably Class D switching amps—can deliver their power to the speakers more efficiently than traditional hotter-running Class AB or Class A amplifiers. However, Class D AVRs seem to vary widely in subjective sound quality. Read the reviews before you decide.
THX-certified AVRs, when mated with THX-certified speakers, will guarantee the ability to achieve cinema reference volume level at the listening position in a room whose cubic volume is specified by the level of certification. Other measures of performance, compatibility between components, and simplified setup chores are also accounted for in THX certification. Visit THX.com for more information.




Surround Modes

Every modern receiver offers the same basic surround modes to directly decode the soundtracks embedded in today’s software and broadcasts. Although these are often accompanied by additional playback modes, and experimentation is encouraged, you are best advised to play back your content using whatever mode is native to the original soundtrack. This will likely be standard Dolby Digital and DTS embedded on DVDs and the high-resolution lossless formats Dolby TrueHD and DTS-HD Master Audio found now on most Blu-ray Discs. The latter formats are noticeably superior to the earlier lossy compression formats. Most TV broadcasts carry lossy Dolby Digital, and some streaming content from major services, such as Vudu and Netflix, are encoded with Dolby Digital Plus, which provides modest benefits in transmission efficiency or sound quality. Set your new AVR’s surround mode to its automatic setting, and if you’ve selected bitstream audio output from the menus in your Blu-ray player and other digital sources, the receiver should recognize what’s on the source material and set the surround mode accordingly. If you set your player to PCM audio output and hook it up via an HDMI connection, full multichannel decoding will usually take place in the player, and it will be indicated as multichannel PCM on the AVR’s display. The sound quality should be about the same either way, though Blu-ray players can only pass the remote’s button sound effects and secondary simultaneous audio tracks associated with the disc extras if the player is set to PCM.
The next suite of essential listening modes found in AVRs is for decoding matrix- surround-encoded two-channel sources and converting two-channel stereo recordings or TV shows into quasi surround sound. The best known of these are probably Dolby Pro Logic IIx and DTS Neo:6. These vary in their effectiveness depending on the program material, but one or both are generally available as part of the Dolby and DTS processing package included with the receiver.
Dolby Pro Logic IIz, Audyssey DSX, and even the 11.1-channel DTS Neo:X processing modes, previously used to derive signals for front-wall mounted height and width speakers, were common till recently in mid-level to high-end receivers. These have now been outmoded with the latest object-based surround formats, Dolby Atmos and DTS:X. Instead of using front-wall-mounted speakers, these formats use ceiling-mounted speakers to provide discrete surround effects that can come from directly over the listener. (As an alternative, Atmos systems can use upward-aimed ear-level “Atmos-enabled” speakers that bounce the sound for the height effects off the ceiling.) In our tests so far with Dolby Atmos, using Atmos-encoded Blu-ray Discs, we’ve heard noticeable benefit to installing at least four Atmos height-effect speakers, which would require a minimum 9.1-channel AVR that includes the Atmos processing.
At this writing in late July, DTS:X-enabled AVRs were not yet available for testing, though DTS has stated that their system is flexible in the placement of speakers and we are assuming for now that a Dolby Atmos setup can function for both formats. What remains an issue is the availability of discs and streaming content that carry these discrete object-based soundtracks. Both formats also come with modes that can upmix regular stereo and 5.1-/7.1-channel tracks to derive signals for the height speakers, though until the library of discrete titles ramps up, there’s less incentive to spend the extra money. Still, future-proofers should take good note of what potentially lies ahead.

Compression and Volume Modes

When you need to turn the volume down to avoid disturbing neighbors or family during the loudest passages, dynamic compression and volume normalization help your ability to hear quiet dialogue without being blasted by the special effects and spare you from aggressively riding the volume control during TV shows and movies. Some AVRs still come with a Night mode for this, but they don’t typically achieve the performance of recent third-party offerings by Dolby, Audyssey, and THX. Audyssey Dynamic EQ and THX Loudness Plus (offered on THX-certified receivers) seek to maintain proper frequency balance and dialogue clarity as the volume gets lower, as does Dolby Volume. Dolby Volume, as well as Audyssey Dynamic Volume, can also help minimize swings in loudness as you transition between TV programs and commercials, or between source components with different output levels that you can’t adjust in the source or receiver.





Hi-Res Audio
Increasingly, more and more music is becoming available for download as high-resolution digital audio files—defined as better-than-CD quality. High-resolution audio discs also abound these days—either as SACD releases, or as DVD or Blu-ray Discs offering stereo or multichannel music files. Enjoying these files at their best quality means having a digital-to-analog converter, or DAC, that is compatible with the file type, which may be designated by both a sample rate and bit depth that describes its resolution (for example 96-kilohertz/24-bit or DSD), and/or by the digital wrapper used to package it (such as high-bit-rate MP3 or a compressed lossless file like FLAC or ALAC). The best high-res DACs still tend to be standalone devices that go between your computer and an analog input on your AVR, primarily because they offer “asynchronous” operation that improves sound quality by taking control of the data stream and not relying on the originating computer’s internal clock. But many AVRs now offer built-in DACs that can handle files up to 96-kHz/24-bit resolution or higher, and we’re seeing AVRs now that can directly accept and decode DSD files. A very few AVRs also offer an asynchronous USB connection, but this remains a rarity in the 2015 model crop.

Video Processing

Programming from TV broadcasts or DVDs must eventually be scaled and/or deinterlaced before being displayed on a native 1080p HDTV or one of the new Ultra HD/4K sets. Most often this is done by the display, but some better AVRs offer onboard video processors, often from respected brands like Marvell Qdeo or Anchor Bay, to perform these functions in the receiver, sometimes to better effect. Another benefit to onboard video processing is the ability to cross-convert the analog composite and component video from legacy components like VCRs or game consoles for viewing through the AVR’s HDMI monitor output. But don’t assume onboard video processing is either standard or mandatory for a great audio experience; some very good AVRs skip the fancy video processing to put the money into better-quality audio circuitry and simply act as HDMI switchers.

Auto Setup and Room Correction

Setting up a receiver properly involves making menu selections to tell the AVR how many and what type of speakers you have, what their relative locations are to the primary listening position, their bass capabilities, and what volume level each should be set at relative to the others so the listener hears a coherent soundfield. You can do all this manually—or just run the microphone-enabled auto-setup routine that’s included with most AVRs nowadays. In addition, many receivers will take it a step further and apply equalization across a range of frequencies to smooth out the in-room response, a particularly helpful benefit when it’s applied to the low bass frequencies where most rooms have their worst problems.





Audyssey still has the best-known solutions for auto setup/EQ, with different levels of resolution applied to products at different price points. (You can read more at audyssey.com.) AVR makers that don’t use Audyssey often have proprietary systems that range in quality. Again, you’ll have to read the reviews to see whose systems work best. Either way, you’ll usually have the option to tweak the results or ignore them.

Connectivity

The HDMI interface widely used for digital video source components, switchers, and displays evolves all the time. HDMI 2.0, which handles 4K content at 60-hertz frame rate, is the new kid on the block, and should be accompanied by compliance with the latest digital copy protection scheme HDCP 2.2. (HDMI 2.0a, which some models can be upgraded to at a future date, will allow passthrough of high dynamic range (HDR) 4K content that is planned for the future.) You may still find some AVRs out there offering HDMI 1.4 connections, and, critically, some holdovers from the 2014 model year that offer HDMI 2.0 but without the updated HDCP 2.2 copyright management. If you expect to be able to use your AVR to switch among future 4K source components such as Ultra HD Blu-ray players or streaming media players, you’ll want both HDMI 2.0 and HDCP 2.2. If the AVR features don’t list HDCP 2.2, it’s probably not there.
Legacy inputs for composite, S-video, and component video sources are becoming harder to find on AVRs, so if you have older non-HDMI components, check carefully to make sure you have enough inputs of the right type. One legacy input that’s making a bit of a comeback is the classic phono input, thanks to surging vinyl LP sales. A dedicated phono preamp can be added to any AVR that doesn’t have one.
Among the most used connections on AVRs these days are those that let you take content off your smartphone, tablet, or iPod. Apple AirPlay, straight Wi-Fi, and Bluetooth connections (sometimes via an adapter) are common in various combinations and let you push music from your mobile device to your network-connected AVR. AVRs also offer Made for iPod USB connections, which allow direct digital connection of an iDevice. MHL inputs let you feed audio or video from compatible Android phones.

Network and Internet Services

Nearly all AVRs beyond entry-level will connect to your home network with a wired Ethernet or wireless Wi-Fi link. More often than not, they feature the ability to directly stream music via services like Pandora and Spotify, as well as some facility to capture Internet radio streams from distant lands and your local stations (sometimes a more reliable and better-sounding option than an FM antenna). But these services and many more can also be easily added to an existing AVR with an inexpensive streaming media player. DLNA compliance, another common feature, lets you call up audio and video files from your network-attached computer or hard drive to play on your AVR and HDTV.

Remote Control Apps
Pretty much all the major AVR brands now offer apps that turn your smartphone or tablet into a touchscreen remote for your receiver. All that’s required is a network connection to the AVR and a wireless Wi-Fi network for the app to talk to the receiver. AVRs are notoriously difficult to operate thanks to their myriad capabilities and remote controls that are littered with tiny, poorly labeled buttons, so a good control app can be a godsend, especially for operating your system in a dark room or running a second zone of audio off the AVR (the touchscreen usually allows selection and browsing of network sources, as well as volume adjustment, from inside the second zone). If you’ve got an Apple iPhone, iPad, or iPod touch, or an Android phone or tablet, download the free app for the receiver you’re considering and check it out in demo mode.

source: soundandvision.com