When you start looking into surround sound systems you will probably come across various numbers with decimal points, but it might be confusing to interpret their significance. Enthusiasts and experienced cinema designers may be familiar with them, but for those who are just beginning their journey into home theater, let us simplify and explain what these numbers mean.
To Put It Simply:
Each number represents the number of channels the system has:
The Basics: What is Surround Sound?
Surround sound is a technique that uses multiple speakers to create a realistic and immersive sound field around the listener. Unlike stereo sound, which only uses two speakers to create a left and right channel, surround sound can create a sense of depth and direction by placing speakers in front, behind, and above the listener.
Surround sound can enhance your movie-watching experience by making you feel like you are in the middle of the action. For example, you can hear a car zooming past you from behind, or a helicopter flying overhead. Surround sound can also improve your music-listening experience by creating a more spacious and natural soundstage.
Decoding the Numbers:
The number format in surround sound can be interpreted in two ways:
- The first interpretation involves each number representing the number of speakers in the system, which is a shorthand way of describing the setup. This is the most common way of referring to systems.
- The second interpretation, the technical meaning, assigns each number to represent the number of audio channels that the system can process.
Therefore, it is important to understand the context in which these numbers are used, either to indicate the technical count of audio channels processed or the number of speakers in the system. For instance, one might say their setup is 5.2.4. In this case, looking at the second number, which denotes the LFE or subwoofer, we know there can be only one LFE channel. Therefore, the “2” here signifies that the person is referring to having two subwoofers in their system.
First Number: Main Speakers
The first number in the surround sound setup indicates the quantity of main speaker channels, also called bed layer speakers, present in the system. These speakers play a vital role in producing the main sound effects, dialogue, and music. Positioned strategically around the listener at varying angles, they contribute to the creation of a surround effect.
One of the most common configurations features five main speakers, known as a 5.1 system. This arrangement includes a center speaker, a left and right front speaker, and a left and right rear speaker. As a result, the listener experiences an immersive audio experience. However, some systems have additional main speakers; as many as 7 or 9. The incorporation of more speakers on the sides (called front wides) or at the back (called surround backs) helps to achieve a more encompassing and expansive sound field.
An example of a 5.1 surround sound set up. Property of Dolby
Second Number: The Low Frequency Effects (LFE) Channel
The second number in a surround sound system refers to the LFE channel, which can also indicate the number of subwoofers. As of now, there is only one LFE channel in home surround sound sources, so if a number higher than 1 appears in the second place, it is referring to the number of subwoofers in the system.
The LFE channel is a special audio channel responsible for low-frequency effects like explosions, thunder, or bass. Regular speakers used for the main channels often struggle to reproduce low frequencies effectively, so the LFE channel was introduced. One more more subwoofers are used to handle these low frequencies.
The most common setup includes one subwoofer that manages all of the low-frequency sounds. This is why most systems have a “1” after the first number, like 5.1 or 7.1. Some systems have more than one subwoofer, such as 2 or 4, which means they place multiple subwoofers around the room for a balanced and powerful bass response.
If you are interested to learn more about multi-subwoofer setups, we recommend this article.
Third Number: Height Channels
The third number in the surround sound system denotes the quantity of height channels integrated into the setup. Height channels consist of speakers positioned above the listener, effectively creating a sense of height and verticality within the sound field. Height speakers are typically mounted on the ceiling or placed on specialized stands that angle them upwards. These systems are then denoted with an additional number after the second, for instance, 5.1.2 or 7.1.4. These channels help produce sounds that originate from above for immersive sound formats such as Dolby Atmos and DTS:X. These formats allow sound to envelope the listener in all three dimensions.
If the third number is not included, it means there are no height channels in the setup. The number of height channels typically comes in pairs, like 2, 4, or 6, except for the Auro3D layout, which adds a “Voice of God” speaker positioned above the main listening position.
Common Surround Sound Configurations:
Below are common examples of different surround sound configurations. To get a more comprehensive list, see the Dolby speaker guidelines Here.
The 5.1 home theater system is a popular surround sound setup commonly found in various home theaters. It consists of six channels, including five main speakers and a subwoofer. The front has three speakers: left, center, and right, while two surround sound speakers are positioned at the back or to the side – one on the left and one on the right.
The 5.1.2 surround system expands on the 5.1 setup by including 2 height channels, placed above left and above right, resulting in 8 channels in total. By incorporating height channels, it enables immersive sound formats like Dolby Atmos and DTS:X to generate audio from above the user, creating a captivating 3D soundscape.
A 7.1 surround system is like a 5.1 system, but with two extra rear speakers. It has eight channels and is commonly used in home theaters. With two rear speakers added, the sound becomes fuller and more rounded. This ensures that the two side surround speakers do not have to handle both rear and surround sound, providing a better overall audio experience.
The 7.1.4 surround system takes the 7.1 setup to the next level by introducing 4 height channels, resulting in 12 channels in total. This addition of 4 height channels enhances the listener’s ability to perceive sound location from above, leading to a heightened sense of immersion when enjoying Dolby Atmos and DTS:X content.
More Information on Surround Sound
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