What Does 7.1 Surround Sound Mean

What Does 5.1.2 or 7.1.4 Mean for Surround Sound Speakers, Dolby Atmos and DTS:X?

By Chris Boylan

Dear BPBS,

I've been shopping for a receiver lately and want to get one that does the immersive audio stuff (Dolby Atmos, DTS:X). Some of the receivers say they're 7.2 and other say they're 5.1.4. What do I need and what do these numbers really mean? And can I do the same thing with a soundbar intead of buying a receiver and lots of speakers?

Thanks,

-Peter in Pittsburgh

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Hi, Peter,

Thanks for your question. It's one that we've gotten often over the years.

As the technology of audio and video reproduction advances, things have gotten more complicated. Monophonic tube radios evolved into stereophonic HiFi systems, which in turn evolved into multi-channel surround sound systems. The most recent advance in surround sound -- "immersive sound" -- reproduces sound in all directions, not just in front of and behind the listener, but above our heads too. As these technologies have advanced, a common shorthand has arisen in order to identify the different options available to consumers. And those are the numbers you're asking about.

This series of 3 numbers can be used to describe the number and type of channels in any sound system, from a simple soundbar to an advanced A/V receiver to a professional movie theater surround sound system.

The format is "x.y.z" where:

1. "x" is the number of channels or speakers at or near ear level,
2. "y" is the number of channels or speakers dedicated to low bass reproduction
3. "z" is the number of overhead channels or speakers.

If a system does not have any dedicated height channels, then the last digit is left off.  Here are some examples:

• 1.0 - this is a monophonic sound system with just one speaker reproducing all of the sound.
• 2.0 - this is a standard "stereo system" - it has two speakers to reproduce a stereo soundfield
• 2.1 - this represents a standard stereo system, but it adds a dedicated speaker for low bass reproduction (a woofer or subwoofer)
• 3.0 - this is similar to a stereo system, but it adds a dedicated center speaker between the front left and right speakers. This can help in reproducing movie dialog and commentary clearly.
• 3.1 - as above, but with a dedicated bass speaker (subwoofer).
• 4.0 - A typical 4.0-channel system uses two speakers in the front and two in the rear or side to reproduce surround sound. But a system with 3 speakers in the front (left, center, right) and one in the rear of the room could also qualify as 4.0
• 4.1 - as above, but with a dedicated bass speaker
• 5.0 - this is typically used to describe a traditional surround sound system with three speakers across the front (front left, center and front right) and two speakers on the sides or in the rear to generate surround sound
• 5.1 - as above, but with a dedicated bass channel or subwoofer
• 7.0 - this type of system has three speakers in the front, 2 on the side (side surround) and 2 in the rear (rear surround)
• 7.1 - as above, but with a dedicated bass channel or speaker
• 5.1.2 - this is a "standard" 5.1-channel surround sound system, with the addition of two height channel or speakers that generate sound from above the listener
• 5.1.4 - as above but with 4 height channels or speakers to generate sound above the listener
• 7.1.2 - a standard 7.1-channel system with two additional speakers dedicated to reproducing sound above the listener
• 7.1.4 - as above, but with 4 height channels or speakers

The Dolby Atmos system pictured here includes 12 speakers in a 7.1.4 speaker configuration.

64.4.32? Sure? Why Not?

The numbers can go even higher. Some theatrical immersive sound systems utilize dozens of speakers to reproduce sound as realistically (and immersively) as possible. But a 7.1.4 system is where we find most home theater receivers and speaker systems max out. And in a large living room or even a dedicated home theater, a 7.1.4 channel system is probably good enough to create an enjoyable audio experience anywhere in the room.

It's important to note that not every speaker represented by one of the numbers needs to be in its own physical box. A "3.0" soundbar may have all three of those speakers: front left, center and front right - in a single speaker cabinet. Similarly, not all "height channel" speakers need to be physically placed above the listener in the ceiling or high on a wall. Some height speakers are placed at the listener's ear level but are angled up in order to bounce sound off the ceiling. This gives the illusion of sound coming from above when it's actually being generated from ear height or below.

Can a Soundbar Do That?

While a receiver with dedicated speakers will generally give you the best results, some companies are making soundbars that provide a pretty realistic immersive surround experience. New soundbars from companies such as Yamaha, Samsung and LG are designed to bounce sound off both the side walls and the ceiling in order to create a "5.1.2" immersive surround sound experience from a single soundbar and dedicated subwoofer. These types of systems can be effective at generating an immersive soundfield, but for best results, the listening room must have regular wall and ceiling surfaces that are reflective enough for sound to bounce off and reach the listener's ears from the right directions.

In general, you will get better overall results from a receiver or preamp/amp system that uses dedicated height speakers installed on or in the ceiling, but for those in smaller spaces or in apartments where running a lot of additional wires can be problematic, these reflective and virtual surround sound options offer a viable alternative.

New soundbars, such as the LG SL10Y use side-firing and upward-firing speakers to create a virtual 5.1.2 speaker system from a single soundbar plus a powered subwoofer.

Also, to answer the last part of your question, some receiver makers tout their receivers as "7.2" or "7.2.4" to designate that they have dual outputs for subwoofers, this can be misleading. In many cases, the two subwoofer outputs arenot independently adjustable, so they really shouldn't be counted as separate channels. While it is recommended in many listening rooms to use more than one subwoofer (to compensate for standing waves and room modes), the fine adjustments in level and phase for each subwoofer are typically done on the subwoofer itself, not in the receiver.

I hope that helps!

More on This Topic:

• What's Up with 3D Immersive Sound?
• Immersive Sound Update from Dolby, DTS and Auro
• KEF 5.1.4 Channel R Series Speaker System Review
• New LG Soundbars support 5.1.2 Dolby Atmos and DTS:X

Keep those cards and letters coming! if you have a question for one of our home theater experts, shoot us an e-mail to "Ask The Expert." We'll select among these for future installments in this column. Due to the volume of requests we receive, we cannot reply to each question personally.

What Does 7.1 Surround Sound Mean

Source: https://www.bigpicturebigsound.com/What-Does-5-1-2-or-7-1-4-Mean-for-Surround-Sound-Speakers-Dolby-Atmos-and-DTS-X.shtml

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