Home Theater: Surround Sound Basics

3d1Today’s blog post continues our look at home theater, following yesterday’s Home Theater Basics. Below you’ll find an excerpt from my new book, Home Theater for the Internet Age, regarding surround sound. Most people understand that surround sound involves a speaker arrangement in your living room or dedicated home theater that “surrounds” you (duh).

This is a pretty radical departure from the common arrangement to which most of us (unless you’re a millennial) are acclimated: Sound that emanates from in front of us—typically from the display device, the TV, itself. The old method of projecting sound from the display was rife with deficiencies. First, the speakers built into even the best, most expensive, TVs suck. Period. There’s no physical room in a relatively thin panel for real speakers.

Modern home theater has introduced a more complex audio arrangement in which dedicated, much higher quality, speakers are positioned to the sides or even behind viewers. Because the sound is being projected from locations other than the display panel and is generated by real speakers, surround sound is the cornerstone of true home theater. However, because there’s so many types of surround sound arrangements, the topic can quickly become confusing for non-enthusiasts or those new to home entertainment.

Today we’ll address surround sound configurations. These are the physical layouts of speakers and the logical dispersion of audio channels from TV shows and movies. What’s 5.1? What do the “5” and the “1” mean? Why does your buddy at the office lust for 9.1? Read on to eliminate your confusion.

Also check out Home Theater: More Surround Sound and Home Theater: Surround Sound Formats.

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Curt Robbins


Surround Sound Configurations

As you’ve learned, there are several different physical configuration standards for surround sound, ranging from five to twelve speakers (and sometimes more). Arrangement shorthand is indicated by a decimal number, such as 5.1. This indicates five surround speakers and a single subwoofer. The number of subwoofers is always indicated to the right of the decimal (5.x). A 5.1 AV receiver is capable of outputting to a maximum of five speakers and a single subwoofer. A high-end 9.2 receiver, on the other hand, is capable of driving nine speakers and two subwoofers. If a friend says she has a 6.1 system, you know she has seven speakers total and that one of them is a sub. While uncommon, it’s possible that someone might have, for example, a 5.3 system, in which they have a basic surround complement and three subs (yes, some videophiles install multiple subwoofers).

You’ve already learned the basic role of a subwoofer, or “sub.” In surround sound, the sub carries the LFE, or Low Frequency Effects, channel. Most movies and some TV programming feature an LFE channel (identified as such on your AV receiver). Capable of emitting ultra-low frequencies below 80 Hz, subwoofers are as much about what you feel as what you hear. This low frequency speaker plays in the zone where sound goes from audible to tactile. If a movie indicates that it features “x.1 audio,” it means there’s a dedicated LFE channel (regardless of whether you have a subwoofer to bring this channel to wall-shaking life).

Typically, surround configurations range from 2.0 to 11.2. The most common config is 5.1 (although 2.1, while not providing any surround effect, is also very common). Try not to get surround envy. 9.1 and 11.1 systems are very rare and, arguably, complete overkill for the average consumer. Also, relatively few films and basically no TV shows are encoded in a standard above 7.1 (although this is rapidly changing). Thus, even if you had a fancy 9.1 system, a small percentage of the content you consumed would support it, making it a very expensive upgrade. (I have a 5.1 system and rarely lust for the two additional rear speakers of a 7.1 configuration. If I was going to upgrade, based on the size and layout of my living room, I’d probably never go beyond a 6.1 layout.)

It should be noted that all of these surround configurations are backward compatible, meaning that a 7.1 or 9.1 soundtrack will play just fine on a 5.1 system (or even a 2.0 system) or via headphones. That’s part of the magic of Dolby and DTS and modern home theater receivers.

2.1 & 5.1

Because this book defines home theater as having a minimum of five speakers, a 2.1 setup involving three speakers (two mains and a sub, with no rears) isn’t covered in detail. This type of configuration includes soundbars (see the Soundbars & Theater-in-a-Box section of the Speakers chapter for more info). While this setup doesn’t provide “surround” sound, it can—with even basic equipment—greatly enhance your time with music, TV, movies, and games. It will perform remarkably better than your TV speakers (those built into even high-end display panels are basically an afterthought, producing really crappy sound).

5.1 systems involve two mains (typically floor standing models, but sometimes bookshelf units), a center channel, two rear surrounds (called the left side surround and right side surround), and a subwoofer. Sometimes consumers opt to skip the subwoofer to save money (or because they underestimate the effect it will have during Blu-ray movies). Most videophiles consider 5.1 the entry-level setup for true home theater. If your AV receiver supports 7.1 speaker outputs, a 5.1 system gives you room to grow; simply purchase two additional speakers and you’re in business. While your front three speakers should always be from the same series to ensure timbre-matching, it’s less important for your rear and side surrounds to be from the same line (but still preferable for a variety of reasons).

6.1 & 7.1

Moving up the ladder, more complex surround configurations are 6.1 and 7.1. These involve one or two additional rear speakers, positioned directly behind the viewers, called the left back surround and right back surround—not to be confused with the left side surround and right side surround positions in a 5.1 or larger system. Should you go the extra mile and install one or two extra speakers between your existing surround positions? If you’re a big movie buff and your room is large enough to justify it, maybe. You won’t have trouble finding movies to fill this many speakers; most films today deliver a minimum of 7.1 surround audio channels (even some high-res music albums feature a 6.1 surround mix).

Remember that your AV receiver must support the number of speakers to which you want to expand. If you have a receiver capable of only 5.1, you’ll not only have to purchase one or two additional back surround speakers, but also a new receiver (as you’ve learned, this isn’t cheap, especially if the unit produces clean, robust amplification).

9.1 & 11.1

The average home theater owner probably shouldn’t pursue a 9.1 or larger surround sound configuration. However, it’s important to know one’s options. For very large rooms—or hyper-hobbyists who are pursuing the most realistically surrounding audio environment possible—one of the layouts involving more speakers than a 7.1 system might be appropriate. Of course, it will cost you. You’ll either have to increase your speaker budget or downgrade the quality of your candidates. Those additional speakers—especially if they match your other models—don’t come cheap.

A 9.1 system adds front height channels to the mix (the left height and right height positions), giving—as the name indicates—a taller and seemingly wider front soundstage than a 5.1 or 7.1 system can deliver. 9.1 is the first standard to address the expansion of the front soundstage (whereas 7.1 adds audio imaging to the rear area). Not only would you need to purchase additional speakers to satisfy the needs of a 9.1 system, but you’ll probably need to upgrade your AV receiver to handle the additional amps and terminals. And it hardly makes sense to upgrade without pursuing a few more watts or maybe going Class D. Cha ching.

An 11.1 system goes even further by adding left wide and right wide speakers, positioned at roughly 60 degrees from a forward-facing viewing position (to the left and right of the front height speakers, but closer to the central seating position). This setup results in seven front and four rear speakers. While relatively few movies have been released in 11.1, some of these leading edge films include Rise of the Guardians, Man of Steel, The Croods, Elysium, Turbo, Ender’s Game, Mr. Peabody & Sherman, and How to Train Your Dragon 2.


Curt Robbins is author of the following books from Amazon Kindle:

You can follow him on Twitter at @CurtRobbins, read his AV-related blog posts at rAVe Publications, and view his photos on Flickr.

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