Home Surround Sound

A Review by:  Alphonso Soosay


From the time since Stereophonic sound became trendy in the mid 50’s, the challenge has been on to establish the ultimate “Home Listening Experience”. The conclusion of Dolby Surround mixing was a more balanced listening environment in which the main sounds derive from the left and right channels, the vocal or dialog originated from the centre phantom channel, and the ambience or effects information comes in from behind the listener.

IThe arrival of Dolby Surround:  Then in the mid-70’s Dolby Labs become known, with breakthrough film soundtracks such as Star Wars, Tommy, and Close Encounters of the Third Kind, unveiled a new surround sound process that was more easily adaptable for home use.

Dolby Digital:  Dolby Digital is often referred to as a 5.1 channel system. However, it must be noted that term “Dolby Digital” refers to the digital encoding of the audio signal, not how many channels it has. In other words, Dolby Digital can be Monophonic, 2-channel, 4-channel, 5.1 channels, or 6.1 channels. However, in its most common applications, Dolby Digital 5.1 and 7.1 is often referred to as just Dolby Digital.

The Benefits of Dolby Digital 5.1:  Dolby Digital 5.1 adds both accuracy and flexibility by adding stereo rear surround channels that enable sounds to emanate in more directions, as well as a dedicated Subwoofer channel to provide more emphasis for low frequency earthquake effects. When you explore the history of audio recording and reproducing music and sound, it embarked on with only one channel (mono) and, as technology permitted, it has always made progress to increase numbers of sound channels purely because it’s more realistic sounding. It simulates more closely how we actually hear in a virtual 360-degree field of sound and effects.

The Benefits of Dolby Digital 7.1:  Dolby Digital 7.1 does create a more consistent distribution of the surround effect in a bigger “Home Theatre”. Note: adding extra channels of stereo surround information is not a gimmick.  From experience it’s an honest acoustic attempt to replicate the variety and direction of direct and reflected sounds that occur in real life. Our ears are always out bursting with all kinds of direct sounds as well as with an enormous variety of reflected sounds coming from all directions. Our ear drum and brain process those direct and reflected sounds to give us a sense of the size of the space we are listening in and the distance we are from the source, this is in addition to ambient sounds of all kinds, example: thunder/lightning, earthquake effects, traffic noise, dogs barking, crowd cheering and many that contribute to the sonic clues we hear. Properly set-up 7.1 channels with multi-directional surround speakers are capable of simulating a high degree of realism with both DVD live concerts and movie soundtracks in its musical and sonic impact. Dolby Digital 7.1 system will provide an even more realistic sound experience over 5.1 where space is practical.

Dolby Digital EX:  Dolby Digital EX is in actual fact based on the technology already developed for Dolby Digital 5.1. This formula adds a third surround rear centre channel that is placed directly behind the listener.

DTS (Digital Theatre Systems):  Dolby Labs on the other hand, is not the only player in the home surround sound market, Digital Theatre Systems has also custom-made its surround sound process for home use. Basic DTS is a 5.1 system just like Dolby Digital 5.1, but since DTS uses much less compression in encoding process, I experience that DTS has a improved result on the listening end with acoustic instruments recordings. In addition, while Dolby Digital is mainly intended for the Movie Soundtrack experience, DTS is being used in the mixing and reproduction of Concert Musical performances.

DTS Neo: 6:  In addition to DTS 5.1 and DTS-ES Matrix and Discrete 6.1 channel formats, DTS also offers DTS Neo: 6. DTS Neo: 6, functions in a similar fashion to Dolby Pro-logic II and Ilx, in that, with Dolby Digital receivers and preamps that have DTS Neo: 6 decoders, it will extract a 6.1 channel surround field from existing analogue two-channel material.

So, what is really “Surround Sound”?:  Surround sound refers to the application of multiple audio tracks to envelop the movie watching or music listening audience, making them feel like they are in the inside of the action and being in a live concert. The surround sound movie soundtrack allows the listeners to hear sounds coming from all around them, and plays a large part in realizing what movie makers call “suspended disbelief”. “Suspended disbelief” is when the audience is completely captivated by the movie experience and is no longer aware of their real-world surroundings. Accurate surround sound formats rely on dedicated speakers that literally and physically surround the audience. There is one centre speaker which carries most of the dialog (since the actors usually make conversation while making their on-screen appearance), and part of the soundtrack. There are left and right front speakers that carry most of the soundtrack (music and sound effects), and may carry parts of the dialog (when the director wants to intentionally off-set the source of the dialog to either side, from its default dead-centre screen location). There is a pair of surround sound speakers that is placed to the side (and slightly above) of the audience to provide the surround sound and ambient effects. Ultimately, a subwoofer can be used to reproduce the low and very low frequency effects (LFE) that come with certain earthquake movies and (ect, the foot-stomping bass effects in “JurassicPark” and “Godzilla”).

Dolby Digital:  Dolby Digital (formerly known as Dolby AC-3, where AC-3 is short for audio coding 3) is the de facto surround sound standard in today’s home theatres.  It is the surround sound format used in thousands of movie theatres today. And, since around the month June 1990’s, it has become available for home theatre use by people. Today, a large percentage of the DVD-Video titles come with Dolby Digital surround sound. Dolby Digital content first appeared on Laser-Disc, since DVD’s only emerged in the summer of 1997. (Incidentally, Hi-Fi VHS still only supports up to Dolby Surround Pro-Logic.) Not only is Dolby Digital the standard for DVD-Video, but it is also part of the new coming High Definition TV (HDTV) standard. It is used in Foxtel movies and digital TV channels of digital satellite broadcasting (e.g., Using the “Set-Top-Box” system). Dolby Digital is the successor to Dolby Surround Pro-Logic. The Dolby Digital surround sound format provides up to five discrete (independent) channels (centre, left, right, surround left, surround right; giving it the “5” designation) of full frequency effects (from 20 Hz to 20,kHz), plus an optional sixth channel dedicated for low frequency effects (LFE), usually reserved for the subwoofer speaker. The low frequency effects channel gives Dolby Digital the “.1″ designation. The “.1″ signifies that the sixth channel is not full frequency, as it contains only deep Bass frequencies     (5 Hz to 120 Hz).

“DTS” Digital Surround:  An alternative and competing format to Dolby Digital is DTS Digital Surround or just “DTS as it is popularly known. Like Dolby Digital, DTS is another 5.1-channel surround sound format that is available in movie theatres, and as an optional soundtrack on some DVD-Video movies for home theatre viewing. But unlike Dolby Digital, DTS is not a standard soundtrack format for DVD-Video, and is not used by HDTV or digital satellite broadcasting.

The primary advantage of DTS is that it offers higher data rates than Dolby Digital, leading many home theatre enthusiasts to claim that DTS is better than Dolby Digital in sound quality. The down side is that a DTS soundtrack uses more of the disc’s data capacity due to its higher data rate. This fact plus the fact that DTS is not a standard soundtrack format for DVD-Video makes DTS an optional 5.1-channel surround format that is actually available on only a few DVD-Video movies. There are far more DVD-Video titles with Dolby Digital soundtracks than there are those with the DTS surround sound format.

Dolby “Pro-Logic” Surround :  Dolby Surround Pro-Logic emerged in home theatre systems in early December1990’s. It became the surround sound standard for Hi-Fi VHS, and is still the standard for today’s analogue TV.  Broadcasts, since the Dolby Surround Pro-Logic signal can be encoded in a stereo analogue signal. If you have an “older” Dolby Surround Pro- Logic receiver, you can still enjoy movies from DVD-Video, since all DVD-Video players down-mixes the Dolby Digital information to the Dolby Surround Pro-Logic format, and outputs the signal as a stereo audio pair.

Surround Extended Formats: Dolby Digital EX, THX Surround EX & DTS Extended Surround (DTS-ES) Just when you thought 5.1-channel Dolby Digital and DTS surround sound were enough, at the leading edge today are two new “Extended Surround” formats, namely THX Surround EX and DTS Extended Surround (or DTS-ES for short). The THX Surround EX format is jointly developed by Lucas film THX and Dolby Laboratories, and is the home theatre version of “Dolby

Digital Surround EX”, an Extended Surround sound format used by state-of-the-art movie theatres. Lucas film THX licenses the THX.  Surround EX format for use in receivers and preamplifiers. And as of December 2001, Dolby Laboratories has begun to license what is THX Surround EX under its own name, Dolby Digital EX, for consumer home theatre equipment. (Since THX Surround EX and Dolby Digital EX are equivalent, we will refer to THX Surround EX and Dolby Digital EX interchangeably, with preference for the former since that name has been around longer.) THX Surround EX is the Extended Surround version of Dolby Digital 5.1, while DTS-ES is that of DTS 5.1. The difference between the new Extended Surround formats and their 5.1-channel surround sound counterparts is the addition of a surround back channel, whose corresponding speaker is placed behind the audience. This allows certain soundtrack effects to be presented behind the audience, thereby achieving more enveloping and complete 360. Surround sound. (Remember that in the 5.1-channel surround sound formats, the surround speakers are placed one on each side of the audience not behind them.) Additionally, while the Extended Surround sound format calls for one surround back channel, two surround back speakers are generally recommended for better envelopment. Acknowledging this widely accepted industry position, some high-end receiver manufacturers have introduced “.1 channel” capable receivers, with decoding and sometimes amplification for the two extra surround back channels.

Movies featuring Extended Surround: Star Wars: Episode 1 The Phantom Menace” is the very first movie to feature the new Dolby Digital Surround EX format (though Dolby Digital Surround EX playback is offered only in the finest state-of-the-art movie theatres). Even up until now, only a handful of movies have been released with the new Dolby Digital Surround EX format. The first DVD with THX Surround EX was “Austin Powers: The Spy Who Shagged Me”, while the first with DTS-ES 6.1 Discrete is “The Haunting”. “Terminator 2: Judgment Day (Ultimate Edition)” DVD features both THX Surround EX and DTS-ES Discrete 6.1. Listening to these recordings will give you some ideas of surround mixing.

Alphonso Soosay / 2007

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