1. Presentation 8 – Surround Sound
We have seen that a home theater consists of several components. Probably nothing contributes more to the home theater experience than surround sound. If you visit movie houses regularly, you will accept the surround sound experience immediately. On the other hand, those who are accustomed to conventional sound systems may find the realism a little disconcerting or even distracting at first. But once over the initial shock of being completely enveloped in sound, most people find that surround sound adds immensely to their viewing enjoyment. In this presentation we will introduce you to surround sound, explain the various formats that are available, and point out the number and placement of the speakers in several popular surround sound configurations.

2. At the end of this presentation, you will be able to:
Objectives
At the end of this presentation, you will be able to:
At the end of today’s presentation, you should be able to:

3. Explain the difference between mono, stereo, and surround sound.
Identify the number of channels and speakers associated with 5.1, 6.1 and 7.1 surround sound systems.
Explain the basic differences between Dolby® Surround Sound, Dolby® Digital (AC-3), Dolby® Pro Logic, Dolby® Pro Logic II, Dolby® Digital, DTS, and THX Surround formats.
Draw a simple sketch showing the correct number and placement of speakers in a 5.1, 6.1, and 7.1 surround sound system.
Explain the difference between mono, stereo, and surround sound.
Identify the number of channels and speakers associated with 5.1, 6.1 and 7.1 surround sound systems.
Explain the basic differences between Dolby® Surround Sound, Dolby® Digital (AC-3), Dolby® Pro Logic, Dolby® Pro Logic II, Dolby® Digital EX, DTS, and THX Surround formats.
Draw a simple sketch showing the correct number and placement of speakers in a 5.1, 6.1, and 7.1 surround sound system.

4. The Home Theater System
Video Display
Surround Sound A/V Receiver
Stereo Hi/Fi VCR or DVD Player
Surround Sound Speakers
We have seen that, as a minimum, the home theater system consists of a large screen video display, a surround sound audio/video receiver, a high quality VCR or DVD Player/Recorder, and a serious surround sound system usually consisting of at least five matching speakers. With the exception of the video display, surround sound influences almost all of the components. The A/V receiver determines which surround sound format the system will decode. High fidelity video playback components are needed to take full advantage of surround sound. And finally, surround sound usually determines the number, type, and placement of speakers. As you can see, the home theater goes to great lengths to make the audio portion of the audio/visual experience as realistic as possible.

5. For its first half century, sound reproduction used what we now call a mono sound system. Usually it had a single speaker driven by a single amplifier. To the listener all sounds seemed to come from a single point. For example, when listening to a band, all the instruments seemed to be bunched together at center stage. There was no distinction between the instruments on the right and those on the left; they all seemed to be in the middle. Even when two widely separated speakers were used, they were both driven by the same single channel, so there was still no distinction between right and left. The ear merely tuned in to the speaker that was closest. The sounds were neither spread out, nor separated.
Mono Sound System

6. 2-Channel Stereo Sound System
Left
Channel
Right
Channel
In the 1950s, stereo changed the way people listened to electronically reproduced sounds. The traditional stereo sound system uses two channels, right and left, to spread and separate the sounds. In the case of a band, a microphone on the left side of the stage captures the sounds from the instruments on the left. A different microphone on the right does the same for its side. The left and right channels actually carry different sounds. For the first time, the instruments on the left side of the band stand began to sound as if they were on the left. This system is still widely used today. While far superior to mono, it does not give you the experience of being completely immersed in sound.
2-Channel Stereo Sound System

7. Surround Sound Front Left Right Surround Center
Surround sound carries the concept of sound separation several steps further. Normally it uses at least five speakers – three across the front and two in the back. The idea is to completely immerse the listener in sound. [Click mouse] Then just to make certain that the experience is everything it can be, surround sound adds one final touch.

8. Low Frequency Effect Front Right Rear Center Sub- woofer Or LFE Front
Left
Low Frequency Effect
Its called Low Frequency Effects or LFE. It is yet another channel (that makes six channels total for those who are counting) that is provided with most surround sound program content. And whereas the other five channels carry the entire spectrum of audio frequencies, the LFE channel is devoted to those very low frequencies that rattle a room. [Click Mouse] When implemented with a good subwoofer, LFE can be as much a seismic event as a bass boost.
Rear
Left

9. Surround Sound Dolby® Surround Sound Dolby® Digital (AC-3)
Dolby® Pro Logic
Dolby® Pro Logic II and IIx
Dolby® Digital EX
DTS
THX Surround
Actually what we casually call surround sound comes in many different guises. Seven varieties are listed here, and this is by no means the complete list. Furthermore, as you will see, there are variations even within some of the families shown here. Let’s look at each of these in more detail.

10. Dolby® Surround Sound Early surround sound system
Three channels (Left, right, and rear)
Surround Sound originated with a company called Dolby Laboratories, Inc. Technically, the name Dolby Surround Sound refers to one of their early attempts at immersing a listener in sound. It had a total of three channels: right, left and rear. It is said to have provided a nice overall surround effect, but not the total immersion one expects today.

11. Dolby® Surround Sound Front Left Front Right Surround
Here is a representation of the Dolby Surround Sound system. With only two speakers in front and one in the back it seems down right skimpy by today’s standards. Today, we often and incorrectly refer to any surround sound system produced by Dolby as Dolby Surround Sound or simply Surround Sound. However, the Dolby technologies that have become the de facto standards for surround sound each has a name of its own.
Surround

12. Dolby® Pro Logic
Creates four channels of sound from just two audio channels.
Found on most VHS movie tapes.
Used in some analog TV programming.
Requires a receiver with a Pro Logic (or better) decoder.
One of the first surround sound formats to be widely accepted was the Dolby Pro Logic format. It was the “standard” for years and is still used today. It creates four channels of sound (left, center, right, and surround) from just two recorded audio channels (left and right). The information for the center and surround channels is derived from the left and right channels. Most VHS movies include the audio channels needed by the Dolby Pro Logic decoder. If your equipment does not have the Dolby Pro Logic (or better) decoder, you will hear stereo. If you do have the proper decoder, and four or more properly wired and placed speakers, you will be treated to a pleasing surround sound – minus the teeth rattling LFE.

13. Dolby® Pro Logic Surround Sound
Center
Front
Left
Front
Right
Dolby® Pro Logic Surround Sound
With its three front speakers and its single surround channel, Dolby Pro Logic was the standard for many years. Most modern systems also handle this format in order to support the millions of existing tapes that were recorded when this format was king.
Surround

14. Dolby® Pro Logic VHS Tape Dolby Pro Logic Encoder Or Stereo TV
Right
Dolby
Pro Logic
Encoder
Center
Right
Left Or
A few years ago, most movies and stereo TV broadcasts started life as four channels: Left, right, center and a single surround channel. Unfortunately, neither VHS tape nor analog TV broadcasts could handle this format directly. So the Dolby Pro Logic encoder was used to encode the four channels into the two channels (left and right) required by the media of the day.
Left
Surround
Stereo TV
Broadcast

15. Dolby® Pro Logic VHS Tape Dolby Pro Logic Decoder Or Stereo TV
Right
Right
Center
Left Or
Left
In the home, a Dolby Pro Logic decoder received the left and right channels from either the VHS tape or the analog TV broadcasts and recreated the center and surround channels as well as reproducing the left and right channels. While new programming is rarely produced in this format today, there are still millions of video tapes of movies and other stereo TV broadcasts that were originally recorded in this format. So while there are much more advanced surround sound decoders available today, most are capable of supporting this older Pro Logic format.
Surround
Stereo TV
Broadcast

16. Dolby® Pro Logic II
Attempts to create a surround sound like experience from two channel stereo sources.
Designed to drive five or six speakers.
Front – right, center, and left;
Surround – right and left.
Subwoofer
Dolby Pro Logic II carries the concept one step further by attempting to create the surround sound experience from virtually any stereo source. With as little as two channels of audio to work with, it can create a somewhat immersive experience. It is said to bring new life to old movies or CDs in the home theatre environment by recreating a fairly convincing 5.1 simulation.

17. Dolby® Pro Logic II Surround Sound
Sub-
woofer
Or LFE
Center
Front
Left
Front
Right
Dolby® Pro Logic II Surround Sound
Dolby Pro Logic two drives either five speakers in the configuration shown here; or the six speaker configuration shown here. [Click Mouse]
Rear
Left
Rear
Right

18. Dolby® Pro Logic IIx Derives a total of eight channels
In a 7.1 configuration.
Front: Left, center, right
Four surround channels
Subwoofer
The latest wrinkle in the Pro Logic family is called Pro Logic IIx. Using the same input sources as Pro Logic and Pro Logic II, it derives a total of eight channels. This allows it to create a 7.1 environment with three front speakers, four surround speakers as well as a subwoofer. Many of today’s best surround sound receivers support the Pro Logic IIx format.

19. Dolby® Pro Logic IIx Surround Sound
Sub-
woofer
Center
Front
Left
Front
Right
Dolby® Pro Logic IIx Surround Sound
Often the eight speakers of the Dolby Pro Logic IIx are arranged like this. Notice that the two extra surround speakers are positioned at the sides of the listener.
Rear
Left
Rear
Right

20. Dolby® Digital Also called AC-3 5.1 System 6 Channels
Front – right, center, and left
Surround – right and left
LFE
Used on DVDs, HDTV, and DBS.
Today, Dolby Digital is the most widely used surround sound system. Also called AC-3, it usually has 6 separate and independent channels. By separate and independent, we mean that none of these channels are derived from other channels as in Dolby Pro Logic II family. Five of these channels provide the full range of audio frequencies – three in the front in the familiar right, left and center arrangement and two surround channels for the rear or the sides of the listener. The sixth is the LFE channel which handles only the low frequencies and drives the subwoofer. While these six channels can recreate beautiful music, they really earn their keep by bringing movies to life. You will find Dolby® Digital soundtracks on DVDs, high definition television (HDTV) broadcasts, and digital broadcast satellite (DBS) programming.

21. Dolby® Digital Dolby Digital Encoder DVD Right Center Left Digital
Bitstream
Srnd. R
To see how Dolby Digital works, let’s assume that a movie was originally produced with a Dolby 5.1 Surround Sound Soundtrack. We now want to produce a DVD of that movie. The six channels of the sound track are applied to a Dolby Digital Encoder. The encoder converts the 6 channels of information into a single digital bit stream. This bit stream is then recorded as a series of lands and pits on the surface of the disk.
Srnd. L
LFE

22. Dolby Digital Decoder 6- Channel Amp
A/V
Receiver
DVD
Player
Right
Dolby
Digital
Decoder 6-
Channel
Amp
Center
DVD
Digital
Bitstream
Left
Srnd. R
In the home theater, the processed is reversed. Your DVD player recovers the digital bit stream and applies it to the A/V Receiver. A decoder in the A/V Receiver converts the digital bit stream back into its original 6-channel form. Each of the six signals is then sent to separate amplifiers usually within the A/V receiver itself. In turn, these amplifiers drive the six speakers.
Srnd. L
LFE

23. Dolby® Digital Surround Sound
Sub-
woofer
Or LFE
Center
Front
Left
Front
Right
Dolby® Digital Surround Sound
The Dolby® Digital surround sound system is the current standard for most music, most motion pictures, and for digital television. It is a six channel system arranged in the 5.1 scheme. The “five” stands for the five standard speakers that are placed around the listener – three in front and two behind. The “dot one” is a sixth channel called the LFE that is sent to the subwoofer.
Rear
Left
Rear
Right

24. Advantages of Dolby® Digital
Most commonly used DVD and HDTV multi-channel format.
Will also decode Dolby® Pro Logic format.
Perhaps the chief advantage of Dolby Digital is that it is the most common DVD and HDTV format. An added bonus is that it will also decode the Dolby Pro Logic format, which we discussed earlier.

25. DTS Decoding An alternative to Dolby Digital Theater Systems, Inc.
6 channels in the same 5.1 configuration.
DTS Decoders are included in most 5.1 surround processors.
An alternative to the many Dolby formats is DTS Decoding from Digital Theater Systems, Inc. Like Dolby, several different DTS formats exist. The most popular is a 6-channel scheme that provides separate channels to five full-range speakers and one subwoofer. Sound familiar? It should, it’s the same 5.1 configuration shown earlier. While DTS uses different techniques than those used by Dolby, it obtains similar results. Even though the two techniques are not inherently compatible, most equipment that has Dolby® Digital capability is also likely to handle the DTS format. DTS does not compress the sound data as much as Dolby Digital does. DTS fans claim that this produces more accurate sound. If so, it comes at the expense of more data which means that extras such as alternate scenes, out takes, commentaries, etc. are not included on the DVD. At the time this was written, DTS fans did not have the depth of programming material to choose from as the Dolby fans. However, the popularity of DTS is said to be growing.

26. Advanced Techniques Dolby Digital EX DTS-ES
THX Surround and THX Surround EX
Like everything else in the world of electronics, surround sound marches on. More advanced techniques have been proven and have moved to the market place. These include Dolby Digital EX which not only supports the older and more popular Dolby Digital but provides advanced techniques that support 6.1 and 7.1 surround channels. On the DTS side, DTS-ES supports the older DTS 5.1 as well as newer 6.1 and 7.1 schemes. Finally, there is THX Surround and THX Surround EX.

27. THX Surround
Product of LucasFilms® of Star Wars and Indiana Jones fame.
Uses advanced and subtle techniques to create a true 360° sound experience.
The THX-licensed home theater systems are based on Dolby Surround Pro Logic and Dolby Digital decoding.
Equipment that carry the THX trademark has been evaluated by LucasFilm and found to meet the standard.
THX Surround is yet another system and some say the most advanced yet. It is the brain child of LucasFilms, the company that produced the various Star Wars and Indiana Jones sagas. Originally developed for movie theaters, a home version eventually evolved. Using a series of advanced and subtle techniques, it attempts to create a true 360-degree sound experience. The THX-licensed home theater systems are based on Dolby Surround Pro Logic and Dolby Digital decoding. At the time of this writing there is little media available in this format and few receivers support it. The equipment that does carry the THX trademark has been evaluated by LucasFilms and found to meet their exacting standards. THX Surround refers to the original 5.1 format, while THX Surround EX refers to the 6.1 and 7.1 format.

28. - - - - - - FRONT SPEAKERS SURR. SPEAKERS R L R L + + + + + + CENTER
SUB
WOOFER
Today, most good A/V amplifiers support the most popular surround sound formats. While you should check the specs to make certain, it is a good bet, that a high quality receiver will support Dolby Pro logic, Dolby Digital, and DTS. You can also tell a lot by looking at the back of the receiver. There is one pair of posts for each speaker. Here there are six pairs indicating six speakers, also the names tell us this is the familiar 5.1 arrangement. Two wires connect to each speaker. Pay particular attention to the labeling and make certain that the wires go to the correct speaker. Also, be sure to observe polarity. This means connecting the plus lead on the amplifier to the plus lead on the speaker. - -

29. 5.1 Surround Sound Center Sub- woofer Front Left Front Right Rear Left
The number of speaker posts does not tell us the type of decoders used. But they do indicate that, whatever the coding scheme, the speakers are arranged in the familiar 5.1 configuration.
Rear
Left
Rear
Right

30. 6.1 Surround Sound Sub- woofer Center Front Left Front Right Surround
If there are seven speaker posts, chances are, it supports the 6.1 configuration shown here.
Surround
Right
Surround
Left
Surr. Center

31. 7.1Surround Sound Sub- woofer Center Front Left Front Right Surr. Left
And finally, eight speaker posts probably means it supports the 7.1 configuration. We will have more to say about the exact placement of all these configurations in a later presentation.
Surr.
Left
Surr.
Right

32. End
This concludes this presentation.