A Review By: Alphonso Soosay
The insight of this article is to surround a preview of audio technologies that has been and is in the consumer market. Today’s common audio term with “Home Theatre’s” is the “Dolby Digital Surround Sound”, an experience that is being enjoyed in home theatres all over the world.
Not long ago, the world has entered into the “Third Age” era of reproduced sound, which is “Dolby Digital Surround Sound”.
The “Stereo” era was the “Second Age” and before that the “Monophonic” era was the “First Age”.
During the “First Age” era, the idea was simply to reproduce the timbre of the original sound. No attempts were made to reproduce directional properties or spatial realism.
The “Second Age” has provided great listening pleasures for four decades. Stereo has also improved the reproduction of timbre and added two dimensions of space. The Right and Left channel musical performers across a stage.
Monophonic sound is a single-channel, unidirectional construction of sound reproduction. All essentials of the sound recording are focussed using one amplifier and speaker matched together. No matter where you stand in a room, you hear all the elements of the sound equally (except for room acoustic variations). To the “Ear”, all the elements of the sound, voice, instruments, effects, etc. Appear to originate from the same point in space. It is as if everything is “expressed “to a single point. If you connect two speakers to a Monophonic amplifier, the sound will appear to originate at a point equidistant between the two speakers, creating a “presence ” channel.
With Stereophonic Sound, it has a more affirmative type of sound reproduction. Although not totally practical, but some stereophonic sound lets the listener experience the true sound staging of the live performance. It all depends on how the final mix is created.
The Stereophonic Process:
The most important characteristic of Stereophonic sound is the separation of sounds across the two channels. The recorded sounds are then mixed in such a way that some musical instruments are channelled to the left channel of the soundstage; others to the right channel. One positive result of stereo sound is that listeners experience the correct sound staging of symphony orchestra recordings, where sounds from the various instruments more naturally emanate from different parts of the stage.
However, monophonic elements are also included. By mixing the sound from a lead vocalist in a band, into both channels, (Left and Right) the vocalist appears to be singing from the “phantom” centre channel, between the left and right channels.
Limitations of Stereo Sound:
With Stereophonic Sound it was a sparkle through for consumers of the early 60’s, but it did have limitations at that time, Because a good number of recordings at that time resulted in a “ping-pong” effect in which the recording mixing emphasized the difference between the left and right channels too much with not enough mixing of basics in the “phantom” centre channel. Even though the sounds were more stereo, but it did lack the ambience information, such as acoustics and other essentials.
It actually left Stereophonic sound with a “wall effect” in which everything striped you from front and lacked that natural sound of back wall reflections or other natural acoustic nitty-gritty’s.
Just after Stereophonic sound was introduced, between the late 1960’s and early 1970’s two developments became known that endeavoured to deal with limitations of stereo sound. It was the Four Channel Discrete and Quadraphonic Sound.
Four-Channel Discrete the one with problems:
The problem with Four Channel Discrete, in which four identical amplifiers (or two stereo ones) were needed to reproduce sound, it was extremely expensive (those were the days of Tubes and Transistors, not IC’s and Chips).
Also, its sound reproduction was really only available on Broadcast (two FM stations each broadcasting two channels of the program simultaneously; obviously you needed two tuners to receive it all), and four channel Reel- to-Reel audio recorder/playback, which was also very expensive at that time.
In addition to that, Vinyl LP’s and Turntables could not handle playback of four channel discrete recordings. Although several interesting musical performances were simulcast using this technology (with a co-operating TV Station broadcasting the Video Section), the whole set-up was too problematic for the ordinary consumer.
Quadraphonic A More Realistic Surround Approach:
Winning a more practical and affordable approach to Surround Sound reproduction, than that of “Four Channel Discrete”, the “Quadraphonic” system consisted of matrix encoding all four channels of information within a two channel recording. The practical result was that ambient or effects sounds could be imbedded in a two channel recording that could be retrieved by a normal stereo turntable stylus and recognized through to a receiver or amplifier with a Quadraphonic decoder.
In real meaning, “Quad” is the ancestor of today’s Dolby Surround (it’s a piece of evidence, if you own any old Quad piece of equipment they still have the ability to decode most analogue Dolby Surround signals). Although Quad had the promise to bring affordable surround sound to the home environment, the requirement to buy new amplifiers and receivers, additional speakers, and ultimately lack of consensus amongst hardware and software makers on standards and programming, Quad basically ran out of control before it could truthfully enter the audio market.
The Arrival Of Dolby Surround:
Then in the mid-70’s came, Dolby Labs, with innovation film soundtracks such as Star Wars, and Close Encounters of the Third Kind, this unveiled a new surround sound process that was more simply adaptable for home use. Also, with the prelude of the Hi-Fi Stereo VCR and Stereo TV Broadcasting in the 1980’s, there was a bonus pathway for which to gain public acceptance of Surround Sound. Up to that stage, listening to the sound portion of a TV Broadcast or VCR tape was like listening to a tabletop AM radio.
Dolby Surround Sound Practical for the Home:
With the capability of encoding the same surround information into a two channel signal that was encoded in the original Movie or TV soundtrack, software and hardware manufacturers had a new motivation to make affordable Surround Sound components. Associate Dolby Surround processors became available for those that already owned Stereo only receivers. As the popularity of this experience reached into the more and more homes, more affordable Dolby Surround Sound receivers and amplifiers became accessible, finally making Surround Sound a permanent part of the Home Entertainment Experience.
Dolby Surround Basics:
With Dolby Surround process it involves encoding four channels of information (Front Left, Centre, Front Right, and Rear Surround into a one or two channel signal. A decoding chip then decodes the four channels and processes them to the appropriate destination, the Left, Right, Rear, and Centre (centre channel is derived from the LR front channels).
The result of Dolby Surround mixing is a more balanced listening environment in which the main sounds derive from the left and right channels, the vocal or dialog originates from the centre channel, and the ambience or effects information comes in from behind the listener. In musical recordings encoded with this process the sound has a more natural feel, with better acoustical cues. With movie soundtracks the sensation of sounds moving from front to rear and left to right adds more realism to the viewing/listening experience by placing the viewer in the action. Dolby Surround is basically effective in both musical and film sound recording.
The Limitation of Dolby Surround:
Dolby Surround do have its limitations however, with the rear channel being basically passive, it lacks specific directionality. Also, overall separation between channels is much less than a typical Stereophonic recording.
Dolby Pro Logic:
Dolby Pro Logic takes care of the limitations of standard Dolby Surround by adding firmware and hardware elements in the decoding chip that emphasize important directional cues in a movie soundtrack. In other words, the decoding chip will add emphasis to directional sounds by increasing the output of the directional sounds in their respective channels.
This process, although its not important in musical recordings, but is very effective for film soundtracks and adds more accuracy to movie effects such as gun shots, glass shattering/breaking, thunder, lightning, explosions, planes flying overhead, etc. There is greater separation between Channels. In addition, Dolby Pro Logic creates a dedicated centre channel that more accurately centres the dialog (this necessitates a centre channel speaker for full effect) just like in a movie soundtrack.
Limitation of Dolby Pro-logic:
Even though, Dolby Pro-Logic is an excellent refinement of Dolby Surround, its effects are derived strictly in the reproduction process, and even though the rear surround channel may employ two speakers, they are still passing a monophonic signal, limiting rear-to-front and side-to-front motion and sound placement cues.
Dolby Digital is also referred to as AC-3 or the accepted 5.1 channel system. Nevertheless, it must be noted that its term “Dolby Digital” refers to the digital encoding of the audio signal, not how many channels it has. In other words, Dolby Digital can also be monophonic, 2-channel, 4-channel, 5.1 channel or 7.1 channels. However, in its most common applications, Dolby Digital 5.1 and 6.1 is often referred to as Just Dolby Digital.
The Benefits of Dolby Digital 5.1:
Dolby Digital 5.1 includes both precision and flexibility by adding stereo rear surround channels that enable sounds to emanate in more directions, as well as a supportive Subwoofer Channel to place forward more emphasis in the low frequency range.
Also, unlike Dolby Pro- logic which requires a rear channel of only minimal power and limited frequency response, Dolby Digital encoding/decoding requires the same power output and frequency range as the front two main left and right channels.
Dolby Digital encoding on Blu-Ray, DVD’s and Satellite Set top box programming is very common and has solidified this format in the marketplace. Since Dolby Digital differentiates its own encoding process, you need to have a Dolby Digital receiver or amplifier to accurately decode its signal, which is transferred from a component, such as a Blu-Ray, DVD player, and Set top box via either a digital optical connector or digital coaxial connector.
Dolby Digital EX:
Dolby Digital EX is in actual fact based on the technology already developed for Dolby Digital 5.1. This process adds a third surround channel that is placed directly behind the listener.
In other words, the listener has both a front center channel and, with Dolby Digital EX, a rear center channel. If you are losing count, the channels are labelled: Left Front, Center, Right Front, Surround Left, Surround Right, and a Subwoofer, with a Surround Back Center (6.1) or Surround Back Left and Surround Back Right (7.1) (which would actually be a single channel in terms of Dolby Digital EX decoding). This obviously requires another amplifier and a special decoder in your A/V Surround Receiver. The 7.1 surround receiver has all the necessary software.
The Benefits of Dolby Digital EX:
What is the improvements of the EX enhancement to Dolby Digital Surround Sound?
In actual fact, it boils down to this: With Dolby Digital, much of the surround sound effects move towards the listener from the front or sides. However, the sound loses some directionality as it moves along the sides to the rear, making a precise directional sense of sounds from moving objects moving or panning across the room difficult. By placing a new channel directly behind the listener, panning and positioning of sounds emanating from the sides to the rear are much more precise. Also, with the additional rear channel, it is possible to originate sounds and effects from the rear more precisely as well. This places the listener even more in the center of the action.
Dolby Digital EX Compatibility:
Dolby Digital EX is completely compatible with Dolby Digital 5.1. Since the Surround EX signals are matrixes within the Dolby Digital 5.1 signal, software titles encoded with EX can still be played on existing Blu-Ray, DVD players with Dolby Digital outputs and decoded in 5.1 on existing Dolby Digital Receivers.
Although you may end up buying new EX-encoded versions of DVD’s you may have already in your collection when you finally get your EX setup running, you can still play your current Blu-Ray, DVDs through a 6.1 Channel Receiver and you will be able to play your new EX-encoded discs through a 5.1 channel receiver, which will just preserve the additional information with the current 5.1 surround system.
Difference between Dolby Pro Logic II & amp; Dolby Pro Logic IIx:
While Dolby pro-logic reproduces monaural 100Hz to 7 kHz rear surround channel, Dolby Surround pro-logic ll reproduces stereo 20Hz to 20 kHz rear channels. It recreates precise directionality and spatial expansiveness using all your speakers with a more natural sounding 5.1 channel surround sound for a new level of Home Theatre entertainment.
The up-graded pro-logic llx is an extension of Dolby pro-logic ll technology, it expends the playback system configuration and maintains the sonic clarity, and it is similar in regards to EX in Dolby digital EX. The sonic goals in developing Dolby pro-logic llx was to improve surround envelopment, enhanced sense of spatial depth, improve directionality, more enveloping, more involving, more precise and has a larger listening area, commonly referred as the sweet spot.
Surround Sound for Music:
Furthermore, with surround system such as Dolby Digital and Dolby Digital-EX is primarily designed for movie viewing, there is a lack of an effective surround process for music listening.
In fact, many sensitive audiophiles reject much of the surround sound systems, including the new SACD (Super Audio CD) and DVD-Audio multi-channel audio formats, in favour of the traditional two-channel stereo playback.
Yamaha electronics have developed sound enhancement technologies (referred to as DSP Digital Sound-field Processing) that can place the source material in a virtual sound environment, such as a jazz club, concert hall, or stadium, but cannot “convert” two or four channel material into a 5.1 format.
The Benefits of the Dolby Pro Logic II Decoding Process:
Keeping this in mind, Dolby Labs has come to the rescue with an enhancement to its original Dolby Pro-Logic technology that can create a “simulated” 5.1 channel surround environment from a 4-Channel Dolby Surround signal (dubbed Pro-Logic II). Although not a discrete format, such as Dolby Digital 5.1 or DTS, in which each channel goes though its own encoding/decoding process, Pro Logic II makes an effective use of matrixing to deliver an adequate 5.1 representation of a Blu-Ray, DVD or Music soundtrack. With advancements in technology since the original Pro-Logic scheme was developed over 10 years ago, channel separation is more distinct, giving Pro Logic II the character of a discrete 5.1 channel scheme, such as Blu-Ray, DVD Dolby Digital 5.1.
Extracting Surround Sound from Stereo Sources:
A new advantage of Dolby Pro Logic II is the ability to adequately create a surround listening experience from two-channel stereo music recordings. I myself have been less than satisfied trying to listen to two-channel music recordings in surround sound, using standard Pro Logic. Vocal balance, instrument placement, and transient sounds always seem to be somewhat unbalanced. There are, of course, many CD’s that are Dolby Surround or DTS encoded, which are mixed for surround listening, but the vast majority are not and thus, can benefit from the application of Dolby Pro-Logic II enhancement. Dolby Pro Logic II also has several settings that will allow the listener to adjust its soundstage to suit your specific tastes.
These settings are:
Dimension control, which allows users to adjust the soundstage either towards the front or towards the rear. Center width control, which allows variable adjustment of the center image so it may be heard only from the Center speaker, only from the Left / Right speakers as a “phantom” center image, or various combinations of all three front speakers. Panorama Mode, which extends the front stereo image to include the Surround speakers for a wraparound effect.
A final advantage of a Pro-Logic II decoder is that it can also perform as a “regular” 4-channel Pro-Logic decoder, so, in real meaning, receivers that include Pro-Logic decoders can, instead, include Pro Logic II decoders, giving the end user more flexibility, without having to having the expense of requiring two different Pro-Logic decoders in the same unit.
Dolby Pro Logic IIx:
Finally, a more recent peripatetic of Dolby Pro Logic II is Dolby Pro Logic Ilx, which expands the extracting capabilities of Dolby Pro Logic II, including its preference settings, to 6.1 or 7.1 channels on Dolby Pro Logic Ilx-equipped receivers and preamps. Dolby Pro Logic Ilx selves to deliver the listening experience to a greater number of channels without having to remix and reissue the original source material. This makes your vinyl record and CD collection easily adaptable to the latest surround sound listening atmosphere.
Dolby: Virtual Speaker:
Even though the trend headed for towards surround sound relies; on adding additional channels and speakers, the requirement of multiple speakers around an entire room is not always practical. Having that in mind, Dolby Labs has developed a way to create a fairly accurate surround experience that gives the illusion that you are listening to a complete surround speaker system, this utilizing just two speakers and a subwoofer.
Dolby Virtual Speaker, when used with standard stereo sources, such as CD, it creates a wider sound stage. Then again, when stereo sources are combined with Dolby Pro-logic II or Dolby Digital encoded DVDs are played, Dolby Virtual speaker creates a 5.1 channel sound image using technology that takes into account sound reflection and how humans hear sound in a natural environment, enabling the surround sound signal to be reproduced without needing five or six speakers.
DTS (Digital Theatre System):
Dolby Labs are not the only player in the home surround sound market; Digital Theatre Systems has also adapted its surround sound process for home use. Basic DTS is a 5.1 system just like Dolby Digital 5.1, but since DTS uses less compression in encoding process, many feel that DTS has a better result on the listening end. It’s more natural. In addition, while Dolby Digital is mainly intended for the Movie Soundtrack experience, DTS is being used in the mixing and reproduction of Live and Studio Musical performances.
A number of CD only players now come equipped with DTS outputs that allow a DTS-equipped amplifier or receiver to decode the DTS signals imprinted on “select” DTS-encoded music CD’s.
This new surround technology incorporates a rear centre channel for further add to the realism and accuracy of “Home Theatre” systems. DTS has come up with its own 6.1 and 7.1 channel, systems, in competition with Dolby Digital EX, DTS-ES Matrix and DTS-ES 6.1 Discrete. Basically, DTS-ES Matrix can create a center rear channel from existing DTS 5.1 encoded material, while DTS-ES Discrete requires that the software being played already has a DTS & amp; ES Discrete soundtrack. The benefits of this technology are that it has a more realistic flyover and fly-around effects. It produces a more stable image for atmospheres and surrounds effects, and also a more consistent 360 degree surround sound effect throughout the home viewing room.
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 receivers and preamps that have DTS Neo-6 decoders, it will extract a 6.1 channel surround field from existing analogue two-channel audio system.
Dolby Labs and DTS are not the only forces in surround sound technology; SRS Labs also has innovative technologies that can enhance the home theatre experience. True-Surround is a sound-scheme that has the ability to take multi-channel encoded sources, such as Dolby Digital, and reproduce the multi-channel surround effect by just using two-speakers. The result is not as impressive as true Dolby Digital 5.1 (the front and side surround effects are impressive, but the rear surround effects fall a little spill out, with the sense that they are coming from just to rear of your head rather than from the back of the room). However, with many clienteles unwilling to fill their room with six or seven loudspeakers, True-Surround does give the ability to enjoy 5.1 channel sounds within a normally-limited two channel listening environment.
SRS Circle Surround and Circle Surround ll:
Circle Surround, on the other hand, move towards surround sound in a unique way. While Dolby Digital and DTS approach surround sound for a precise directional standpoint (specific sounds emanating from specific speakers only),
Circle Surround emphasizes sound immersion. To accomplish this, a normal 5.1 audio source is encoded down to two channels, then re-decoded back into 5.1 channels and redistributed back to the 5.1 speakers (plus subwoofer) in such a way as to create a more immersive sound without loosing the directionality of the original 5.1 channel source material. The results are more impressive than that of True-Surround. First, panning sounds such as flying planes, speeding cars from left to right, or trains zipping past sound even as they cross the sound stage; often in DD and DTS, panning sounds will “dip” in intensity as they move from one speaker to the next. In addition rear-to-front and front-to-rear sounds flow smoother as well. Second, environmental sounds, such as thunder, rain ‘wind or waves full the sound field much better than in DD or DTS. For example, instead of hearing rain coming from several directions, the points in the sound field between those directions are filled, thus placing you within the rain storm, not just listening to it.
Circle Surround provides an excellent enhancement of Dolby Digital and similar surround sound source material without degrading the original intent of the surround sound mix. Circle Surround II takes this concept further by adding an additional rear center channel, thus providing an anchor for sounds emanating from directly behind the listener.
Surround Sound is not limited to the large-multi channel system, but can also be applied to headphone listening. SRS Labs, Dolby Labs, and Yamaha all have incorporated surround sound technology with the latest headphone listening environment. Generally when listening to audio (either music or movies) the sound seems to originate from within your head, which is unnatural. Dolby Headphone SRS Headphone and Yamaha Silent Cinema employ technology that not only gives the listener an enveloping sound, but removes it from within listener’s head and places the sound field in the front and side space around the head, which is more like listening to a regular home theatre speaker-based surround sound system.
Today’s exciting surround sound experience is the result of decades of development. Surround Sound experience is now easily accessible, practical, and affordable for any consumer. With the amount of audio technological advances that are occurring in the field of Surround Sound, it is no surprise that stereo as we all know will probably and may come up with a new format. The latest HD audio media (SACD and DVD Audio) are now in vital development and are taking into consideration the impact at “You Are In Front Of Me Realism” that has to the end user market. With home theatre surround sound, there are three main players in the field of Surround Sound; they are 1) Dolby Digital, 2) DTS and 3) THX. On the other hand there are many other formats that are trying for a place on the end user market. It only remains to be seen what will happen in the near future. But for now, Dolby Digital, DTS and THX seem to have the attention.
Get physically surrounded with DTS Dolby Digital Sound in your home, it gives the feeling of being in the Movie Theatre.
A Review By: Alphonso Soosay
Audio Recording Engineer / Musician