The Importance of Multichannel Sound

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It’s the element that brings big-screen action to life.


Mar. 08, 2013 — by .(JavaScript must be enabled to view this email address)

When you’re talking about home theater, what’s more important: a big picture or big sound? What if you could only choose one? Most people are undoubtedly drawn to an enormous screen than a suite of boxy-looking speakers. That’s their eye-candy. But having that big sound is what makes the movie really come to life.

Big sound has a far greater impact than a big picture. Don’t believe me? Here’s a test: Watch an exciting lap from a NASCAR race on a 100-inch projection screen and listen to the sound through an iPod-connected speaker on the coffee table. Next, watch that same lap on a 50-inch flat-panel mated to a full-blown surround-sound system complete with a subwoofer. Which experience was the more memorable of the two? Which one captivated your attention and quickened your pulse? If your answer was the big screen and the teeny, tiny iPod speaker, well, you may want to get your ears checked.

It’s important to note that a surround-sound system isn’t only useful in the media or family room. If you have a TV in the bedroom, you’ve surely noticed that most of prime time and late night TV now broadcasts in 5.1. If you’re tired of lowering the volume due to loud music, yet still straining to hear the dialogue, a dedicated center-channel speaker with its own level adjustment will be just what the doctor ordered. Furthermore, if your kids are into gaming, and they have a TV room for playing console games, most if not all modern games feature multichannel soundtracks designed to suck you into the action.

Surround sound may have taken hold in the home theater, but it comes in handy anywhere you enjoy TV-based media.

Surround Sound: Easy as 1-2-3

1. Source: Blu-ray Disc Player. A modern surround-sound system is comprised of a few basic elements. Tackling the signal chain from end to end, it all starts with your source device—the content you wish to listen to through your speakers. Because not everyone “watches television,” and as there’s a lot of variety among cable TV boxes, satellite TV receivers, and rooftop antenna installations, we’re going to focus on movie and music playback. For most people, this will mean a Blu-ray Disc player. You may know that all Bluray Disc players are backwards compatible with DVD. However, you may not know that several Blu-ray Disc players can also handle DVD-Audio and Super Audio CD (SACD) discs. These ill-fated, high resolution, multichannel music formats never fully caught on, but there’s still a lot of great music out there in one or both formats, so it pays to be able to play them.

2. Audio/Video Receiver or Preamplifier/Processor. For many people, the next step in the surround-sound chain is an audio/video receiver (AVR) connected directly to a Blu-ray Disc player. Depending on your Blu-ray Disc player’s decoding capabilities, and the quality of its Digital-to-Analog Converters (DACs), the connection to your AVR will typically be made with either a High Speed HDMI cable or numerous (6 or 8) RCA-style analog audio cables. The more common HDMI method is used when you wish to send a “bitstream” output of the digital signal to your AVR and let the AVR perform the surround decoding. A multichannel analog connection is typically employed when your Blu-ray Disc player sports higher quality DACs than those in your AVR. In this case, you’d want the player to tackle the decoding and rely on your AVR purely for its amplification and switching capabilities. An AVR does many things, but its primary function in a surround-sound system is to decode the incoming signal (e.g. the DTS-HD soundtrack on a Blu-ray movie), provide amplification, and send the appropriate audio channel to each of your connected loudspeakers and subwoofer(s). That is job number one and what matters most is how well it handles this.

Which formats can it decode? Does it use high quality DACs? Can it provide ample power with low distortion? Integrated networking, automated calibration, and colorful user interfaces are nice-to-have extras, but always remember what’s most important. And if the highest quality sound is of paramount importance, forgo a combination AVR in favor of a separate preamplifier/processor and a separate multichannel amplifier (a combination often called “separates”).

3. Loudspeakers. After the AVR or multichannel amplifier has provided the power, the final destination of that Blu-ray soundtrack is your array of loudspeakers. For most television series and movie soundtracks, you’ll be dealing with at least a 5.1 sound mix. In a 5.1 soundtrack, the “5” refers to five fullrange channels around the room (left, center, right, surround right, surround left) and the “.1” is a low-frequency channel dedicated to bass for your subwoofer(s). Speaker options are myriad, from small satellite speakers to on-walls to in-walls to in-ceilings and of course, floorstanding towers. Aesthetics and room logistics often dictate your choice of speaker type, but most audiophiles will agree that freestanding speakers, will outperform all else.

5.1? 7.1? 7.2? 9.1? 11.1?!?!

As you may be aware, many Blu-ray soundtracks go beyond 5.1, some delivering 6.1 or even 7.1 channels of sound. These soundtracks employ one or two “surround back” channels that are centrally located on the rear wall behind the listener. Taking things further, Dolby recently introduced its Pro Logic IIz format, which adds a pair of height channels to the front sound stage, thus transforming a 7.1 soundtrack into a 9.1 experience. Not to be outdone, DTS is pushing the envelope with its new Neo:X technology, an advanced algorithm capable of delivering up to 11.1 channels of sound. However, these advanced surround-sound implementations have yet to go mainstream. Most movies, games and other content is still in 5.1; even 7.1 has yet to become commonplace. Before you even consider wiring your room for 9.1 or 11.1, your money would be better spent investing in additional subwoofers to even out your bass response and give every listening position a better chance at becoming the best seat in the house.

 


Tips for Improving Your Surround Sound

Calibration. Use an inexpensive Sound Pressure Level (SPL) meter and a home theater setup disc such as Disney’s World of Wonder (WOW) to properly adjust speaker level, size, location, and distance from the listener.

Size Matters. Those tiny cube speakers may be cute as a button, but don’t expect them to move a ton of air and deliver deep bass without help from a serious subwoofer.

Matched Speakers. Loudspeaker manufacturers take different approaches when coming up with unique sound signatures for their particular model lines or series. Different materials are used when constructing woofers and tweeters; some enclosures are boxy while others are curved; crossovers are wired differently. The point is, speakers come in all shapes and sizes. You want a consistent quality of sound as music and voices pan from one speaker to the next in your listening room. Although some variation is often possible, using identical speakers in every location is a safe and popular route when designing a surround-sound system.

Proper Crossover. Be sure to select the appropriate crossover frequency—the point at which your subwoofer takes over the heavy lifting for low-frequency sound. THX recommends 80Hz, but small cube speakers may require a setting of 120Hz or even 150Hz.

Proper Placement. Try to keep your front speakers evenly spaced and equidistant from the center channel. Similarly, don’t put one surround speaker right next to your ear and the other 20 feet away. Also, keep your front three channels on roughly the sample plane and place them as close to ear height (when seated) as possible.

Go Lossless or Go Home. Many older Blu-ray titles (and even some of the newer ones) default to standard Dolby Digital. If you don’t go into the pop-up menu, you might never realize there’s a far superior, lossless Dolby TrueHD or DTS-HD Master Audio soundtrack just waiting to be selected.




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