What is Surround Sound? Home Theater Audio Explained

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Surround sound is an essential part of the home theater experience. I’ve used surround sound at home for more than 20 years. From budget, all-in-one systems to high-end speakers powered by an AV receiver.

But, no matter the cost of your gear, the fundamentals of surround sound are the same.

This article will explain surround sound, the different speaker components that make up a basic 5.1 system, and how each speaker contributes to the overall effect.

I’ll also look at more advanced surround formats like Dolby Atmos, which add height channels for overhead audio. If you’re curious about how surround sound works, read on.

Key Points

  • A 5.1 surround system has front left/right speakers, a center channel for dialogue, surround left/right speakers for immersive effects, and a subwoofer for low-frequency bass.
  • The center channel anchors the sound to the screen, while the front speakers create a wide stereo image.
  • Surround speakers create ambient effects from behind to immerse you in the soundscape.
  • Dolby Atmos adds height channels above the listener for overhead audio effects.

What Speakers Are in a 5.1 Surround Sound System?

The most common speaker layout in a multi-channel home theater system is 5.1. There are other layout types with more speakers, and I’ll mention some of these as I go, but let’s keep it simple and first consider the most common form of surround sound.

There are six speakers in a 5.1 surround sound system, and they all do different things.

  1. Front left
  2. Front right
  3. Center
  4. Surround left
  5. Surround right
  6. Subwoofer

You can see in the picture below a standard room layout for these speakers.

5.1 Surround Sound System
5.1 surround sound system

All the speakers need to be positioned carefully, except for the subwoofer, where the location is less critical.

To power these speakers in your home theater, you would usually buy a multi-channel amplifier called an AV receiver, which allows you to connect all the speakers.

However, you can also buy more compact all-in-one soundbar systems to create a surround sound experience in your room.

Your surround sound amplifier can play 5.1 soundtracks encoded in popular audio formats like Dolby Digital, Dolby Digital Plus and DTS 5.1.

Alternatively, your system can use upscaling technologies like Dolby Surround and Pro Logic to create surround sound from a standard stereo soundtrack.

What Does the Center Channel Speaker Do?

The center speaker is critical as it reproduces most of the dialogue in a movie. It’s the most important speaker for movies and general TV viewing.

If you can’t hear the words very well, then you’re not going to enjoy watching movies very much, are you?

The center speaker will usually have a different shape and design than the other speakers, mainly because of its job in delivering the speaking and its location in the room.

The whole unit is often wider than the other speakers in the system, which helps broaden the soundstage when people talk on screen.

Also, a flatter and wider design can make it easier to position the speaker above or below the TV screen discretely.

Klipsch Synergy Black Label C-200 Center Speaker
Klipsch Synergy Black Label C-200 Center Speaker
Image Credit: Klipsch

You can see the typical shape in the popular Klipsch Synergy C-200 home theater center speaker, pictured above. The wide and slim design makes it perfect for placing under your TV screen.

A center speaker may have multiple woofers and tweeters to spread the sound field.

A standard bookshelf speaker usually has the tweeter above the woofer, but the tweeter is generally inline in a horizontal position in a center speaker.

You can use a regular bookshelf speaker as your center speaker, but this might be more difficult to position around your TV – and you won’t have the extra design features available on a dedicated center speaker.

While mainly used for dialogue, in a 5.1 soundtrack, the center speaker will also be required to reproduce some music or sound effects. So, the center should ideally have a frequency response matching the front left and right speakers.

Can you run a surround sound setup without a center speaker? Yes, you can. You can have any speaker layout you like.

In this case, you just need to disable the center speaker in your AV receiver’s setup menu, which will downmix the sound to 4.1 and play the center channel audio through the front stereo speakers.

It won’t sound exactly as intended – because the soundtrack was initially mixed for 5.1 channels – however, some people prefer the sound without a center speaker. FYI, I’m not one of them!

What Do the Front Left and Right Speakers Do?

The front left and right speakers reproduce most of the music and sound effects in a soundtrack. However, they will also be used for dialogue when voices move to the left or right of the screen.

These speakers are crucial and must reproduce a wide range of frequencies, from the low bass in music and effects to high tones in instruments like bells and cymbals. Your subwoofer will handle the really low bass, and I will come to that later.

Because the front speakers are required to reproduce the most important music and sound effects, ideally, they should be of high quality. Although, that might depend on how you will be using your system.

If you only watch occasional movies and general TV on your system, you may get away with spending less money on your front left and right speakers.

However, if you also want to use your system for listening to high-quality stereo music, it will be more important to get good-quality speakers at the front.

The bottom line is if you want to get great sound in your home theater, you shouldn’t skimp on the front three speakers because they lay the foundation of your movie sound.

Ideally, the front left, front right, and center speaker sounds should blend nicely and work together to give the crucial front soundstage in a movie.

Most people will buy a center speaker from the same brand or range as their front left and right, ensuring they sound good together. However, you don’t have to.

Klipsch Synergy Black Label B-100 Bookshelf Speakers
Klipsch Synergy Black Label B-100 Bookshelf Speakers
Image Credit: Klipsch

An example of speakers in the same range is the Klipsch Synergy Black Label B-100 bookshelf speakers, pictured above.

You can see they have the same styling as the center speaker pictured in the last section, and you can be sure that they will work well together because they have comparable technology.

But, if you have speakers of a different brand, you can use equalization on the AV receiver to try and balance the sound. What type of speaker should you use for the front left and right pair?

Well, there are a few different types to choose from – floor-standing, bookshelf or satellite – it doesn’t matter much, and it’s down to your preference. But, they need to work well with the center speaker.

The type of speakers you buy will usually come down to:

  • the size and shape of your room
  • the space you have to install the speakers
  • your budget
  • the type of audio you will be playing through them – movies or music

Small satellite speakers will be easy to install but may not give a big enough sound. Floor-standing speakers will sound great for music and movies but need plenty of space.

So, bookshelf speakers often provide the best balance between sound quality, ease of installation and cost.

What Do the Surround Speakers Do?

The surround left and right speakers mainly reproduce the surround music and effects. They need to reproduce a similar range of frequencies to the front left and right speakers but are less critical than the fronts as they are used less.

Therefore, while they will ideally be similar to the front speakers, saving some money on the surround speakers is more common.

You will not lose so much in overall sound quality – but if you can, keeping the same high-quality speakers throughout the whole system is the best way.

In 7.1 surround sound systems, there are two more speakers at the rear for an even greater sense of space, and these extra speakers have the same requirements as the surround left and rights.

7.1 Surround Sound System
7.1 surround sound system

Like the surrounds, they will ideally be the same quality as the front speakers, but you can get away with less here and may not notice too much.

However, matching the four rear surround speakers in a 7.1 system is usually a good idea. The surround speakers are more likely to be a smaller satellite, bookshelf or in-wall speaker.

SVS Prime Satellite Speakers
SVS Prime Satellite Speakers
Image Credit: SVS

The SVS Prime satellite speakers, pictured above, are an excellent example of high-quality satellite speakers ideal for use in a home theater sound system.

If you have space – and the money – there’s no reason why you can’t use large floor-standing speakers as surrounds. However, it may be more challenging to keep them from overpowering the front’s sound – and get them in the ideal position.

The rear channels don’t usually have much low-end audio in a surround sound mix, and where it exists, much of the low-frequency sound will get routed to the subwoofer.

Therefore, using full-range floorstanding speakers for your surround speakers might waste their potential. They will sound great for 5.1 music, though!

The Different Types of Surround Sound Speakers

Surround speakers are often direct-radiating or monopole speakers. This means they are the ‘normal’ type of speakers you are used to, which fire the sound forward from the speaker – like the ones pictured previously.

They are also the type of speaker generally used at the front of the room. However, there are two special types commonly used as surround speakers, and they are called bipole and dipole speakers.

What Are Bipole Surround Speakers?

Bipole speakers are bi-directional, meaning they have two speaker drivers inside that fire sound in opposite directions simultaneously. You should position bipole speakers to push the sound around the seating area but not directly at the people listening.

Bipole speakers are ideal as surround speakers in a 5.1 or 7.1 system as they spread the audio better than typical direct-firing speakers, creating a less directional sound.

The sound from bipole speakers is in phase, meaning the speaker drivers push out sound at the same time. I won’t bore you with the details, but this is a significant difference compared to dipole speakers.

Bipole speakers are often a small satellite design or sometimes the size of a compact bookshelf speaker.

What Are Dipole Surround Speakers?

Like bipole speakers, dipole speakers also have a pair of speaker drivers in the same cabinet.

But, there is one significant difference. The sound in dipole speakers is out of phase, i.e., when one side is pushing, the other is pulling. The result is a very diffuse sound that is difficult to pinpoint – which is why they are great as surround speakers.

It is essential to install bipole and dipole speakers in the correct position to get the right effect – so you should consult the speaker’s manual before putting them in place.

Bipole speakers are more flexible when it comes to positioning than dipoles. This video gives an excellent summary of the different types of surround speakers:

YouTube video

What Does the Subwoofer Do?

The subwoofer is entirely different from the other speakers. The subwoofer is there for one reason alone – to reproduce the low bass end – and a subwoofer can make a tremendous difference to the perceived quality of your sound system.

Many people don’t have the equipment available to play such low frequencies – but when you have a dedicated bass speaker in your room, you may be surprised how this improves the listening experience.

It can really help to fill out and support the sound from the other speakers. And you don’t need to have it so loud that it shakes the room.

Having it balanced so it just reinforces the bottom end is usually the best way to go. Of course, you can turn it up really loud if you like!

Subwoofers are housed in a large, heavy box – and some look rather cool, and some don’t.

The cabinet itself must be pretty big, as this is the best way to build a speaker to reproduce low bass frequencies properly – the physical size is required to get that very deep bass.

Having said that, you can get many different-sized subwoofers to fit into your space. The cone in a subwoofer for the home can range from around 6 inches to about 15 inches. As a rule, the larger the cone, the better it can reproduce very low frequencies.

However, some smaller subs can pack quite a punch, so don’t discount these entirely, especially if you don’t have much space to install a subwoofer.

Klipsch Synergy Black Label Sub-100 Subwoofer
Klipsch Synergy Black Label Sub-100 Subwoofer
Image Credit: Klipsch

The subwoofer pictured above is the popular Klipsch Synergy Black Label Sub-100 subwoofer, and it would make a perfect match with the bookshelf and center speakers mentioned above.

However, this is more of an aesthetic match. In terms of sound, it’s not so important to have the subwoofer brand match your surround speakers.

Subwoofers designed for home theater are generally powered, which means they have internal amplification. Therefore, your AV receiver doesn’t actually provide power to the sub.

A powered subwoofer will connect to the mains power – and usually get the audio signal via an LFE connection from the AV receiver.

Some subwoofers have wireless connections, making them easier to place in your room. But if not, you can buy a universal wireless audio adapter to connect your AV receiver and subwoofer without a cable – like this SVS Soundpath system here:

Top Wireless Audio Transmitter
SVS SoundPath Wireless Audio Adapter
What Is It: An adapter that sends high-quality wireless audio from your amplifier to a subwoofer or powered speakers.
  • Remove the wires from your home theater installation
  • Works with subwoofers, powered speakers and more
  • 65-foot range
  • Frequency Response: 6Hz to 22kHz +/-1 dB
  • Might not work through walls or in congested wireless networks. If so, try the SVS Tri-Band Wireless Audio Adapter.

You can still use a cable if you wish, but you can place the sub anywhere in the room with the wireless kit.

This is one advantage of a subwoofer – unlike the other speakers, you don’t have to place it in a specific position.

This is because the low frequencies that a subwoofer produces aren’t very directional – meaning it’s hard to tell where the sound is coming from – so you have more freedom to position it in your room.

What Are Dolby Atmos Audio Speakers?

So far, I have discussed the typical speaker types in a 5.1 or 7.1 surround system. But, more recently, there has been another type of speaker introduced in home theater – Dolby Atmos.

Recently, two new movie soundtracks appeared on Blu-ray discs – Dolby Atmos and DTS:X. These are optional soundtracks and appear in addition to the standard 5.1 and 7.1 surround sound audio.

While not identical, Atmos and DTS:X offer the same result: a soundtrack with additional audio intended to create a 3D sound field – especially overhead.

However, to hear this extra audio and create a better audio experience in your room, you need to install more speakers – which is where Dolby Atmos speakers come in.

Although often called Dolby Atmos speakers, you may also see references to height or overhead speakers – which are all the same.

This type of speaker is slightly more complicated than standard surround sound speakers because there are several different types and locations where you can install them.

A Dolby Atmos soundtrack requires a minimum of two dedicated Atmos speakers, usually positioned to add height audio effects, but you can install more.

It is common to have four or even six Atmos speakers in your room – in fact, Dolby Atmos supports a maximum configuration of 24 surround speakers and 10 Atmos speakers.

Whichever speaker layout you want, you must understand that your AV receiver will need enough channels to power the extra speakers.

As I mentioned, an added complication is using different speaker types for Dolby Atmos. You can buy a dedicated Dolby Atmos-enabled elevation speaker, which you place at the same height as your standard surround speakers.

Sony SSCSE Dolby Atmos Enabled Speakers
Sony SSCSE Dolby Atmos Enabled Speakers
Image Credit: Sony

These will bounce the sound off your ceiling down to your listening position – creating the sense that sound is coming from above. Or, you can install speakers high in your room and have the sound coming down to where you are sitting.

These speakers can be in-ceiling models, or you can use standard direct-firing speakers with wall mounts and point them toward the ground.

You can even buy specially-designed wall-mounted elevation speakers for Atmos that angle down and can make installation easier. The Klipsch R-41SA pictured below is a popular example of this.

You can see the angled cabinet at the rear, so the speaker drivers automatically point down toward your listening position when wall-mounted. Depending on your proposed layout, you can install these on the front, rear or side walls of your room.

Klipsch R-41SA Wall-Mounted Dolby Atmos Speaker
Klipsch R-41SA Wall-Mounted Dolby Atmos Speaker
Image Credit: Klipsch

Like surround speakers, you can often get away with spending less money on your Atmos speakers, as the main sound will come from the front of the room.

However, if you already have high-quality surround speakers, you will likely want to spend more and get Atmos speakers of a similar standard.

Although some prefer this to ensure a matching sound and look, they don’t have to be the same brand as your other speakers.

Frequently Asked Questions

What Is 5.1 Audio?

5.1 audio is a surround sound format that uses several speakers around your room to create a more exciting movie listening experience. The speaker layout includes three speakers at the front – a center speaker, front left, and front right – and two more speakers behind you to hear sound effects all around the room. A separate subwoofer speaker for the bass is the .1. Common formats for 5.1 audio are Dolby Digital, Dolby Digital Plus and DTS 5.1, and you will find these on DVDs, Blu-rays and streaming TV services.

What Is a Center Speaker?

A center speaker is used for surround sound audio and will reproduce most of the talking, making it easier to hear what people are saying. It is positioned under or over the screen and between the front left and right speakers.

What Is a Subwoofer?

A subwoofer is a large speaker used for reproducing low bass frequencies. It is usually part of a surround sound speaker system and helps to create an exciting audio experience for movies.

Do You Need Surround Sound For Home Cinema?

You don’t have to install surround sound to enjoy watching your TV – however, a surround sound speaker system will make watching movies, sports and documentaries more enjoyable because it makes the audio much more powerful and thrilling.

What are Dolby Digital and DTS 5.1?

Dolby Digital and DTS 5.1 are surround sound audio formats with five speakers and a subwoofer (5.1) to make movies and music more immersive. Dolby Digital is found on DVDs and is a popular 5.1 format for streaming movies, while DTS 5.1 has better sound quality but needs more storage.

What is Object-Based Surround Sound?

Object-based surround sound is an advanced audio technology that makes sounds in movies and music feel like they’re coming from all around you. It positions individual sounds in 3D space, creating an immersive experience. Dolby Atmos and DTS:X are popular examples of this tech, and to use these formats, you would usually add more speakers to an existing 5.1 system.

How Big Should Surround Speakers Be?

There isn’t a correct size for surround speakers. You can use tower, bookshelf, or small satellite speakers for surround sound, and you just need to decide what works best for your room. Most people will have surround speakers that are the same size – or smaller than the front speakers. Having smaller surround speakers isn’t a problem in many cases, as you will send most of the low frequencies to the subwoofer.

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About The Author

Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has been a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment. You can find out more here.

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