visionhighway » Surround Sound

What is Dolby Digital

Wattsy — Sun, 21 Jun 2009 00:10:58 +0000

First used in cinemas, Dolby Digital is a digital audio signal that was placed on the film between the sprocket holes of the film, Today it is the standard audio format for DVDs. and provides the consumer with a audio system of up to 6 channels which is a perfect match for 5.1 channel amps.
Dolby Digital records, transfers and plays back each channel’s signals with all digital signals. In addition, each channel is recorded independently. Therefore, unlike the conventional analogue Pro Logic system, no signal is pushed into the two channels by matrix treatment. As a result, each channel’s divisional characteristics have been enhanced and stable playback has been achieved. Consumer-format Dolby Digital is basically the same as that for theatre use; only the data rate is different.

Dolby AC-3 was the name used for Dolby Digital prior to the late 1990s. It was designed as a versatile low bit ratecoder for’ Multchannel Digital Audio System’. Today AC-3 generally refers to sound system used on some laserdisc players produced prior to the advent of DVD. Although technically the same audio system, Laserdiscs used an AC-3 RF output that required the use of an amplifier with a AC-3 RF in or a converter to convert the RF signal to the more common SP-DIF format used today. The AC-3 RF output was purely digital RF audio output, the signal has to be decoded by a RF to digital decoder before it can be connected to the digital input of a Dolby Digital Amplifier. It was mostly older high end amplifiers that had a RF decoder input built in to the amplifier but now that laserdisc is a superseded format most high end amps sold today do away with the AC3 RF input in favor of more SP-DIF sockets used by DVD, set top boxes and bluray players.

The next version of Dolby Digital to come along was Dolby Digital EX. It extended the standard 5.1 channel Dolby Digital codec by matrixed rear channels, creating 6.1 or 7.1 channel output in a similar way to how prologic added surround channels to a stero sound track.

The latest version of Dolby Digital you may come across is Dolby TrueHD. Invented as a lossless audio codec it is was developed for the HD-DVD or Blu ray market and is a direct competitor to DTS-HD. It is a 7.1 channel system derived from 8 discretely recorded tracks. Dolby Digital Plus can also be found on Blu Ray or HD-DVD, it is similar in the fact that it is has 7.1 channels but it is considered a lossy audio format being derived from Dolby Digital. It would probably only be used on discs where there was not enough space to fit the TrueHD format.

The general rule of thumb is that if you buy an amp that supports the latest version of an audio format is that it will also support the earlier versions. If you have no intentions of buying a blu ray player and are quite happy with your 5.1 DVDs then there would be no need to upgrade from a Dolby Digital to a TrueHD amp as none of your media will be able to take advantage of the extra features of your new amp.

What is Pro Logic

Wattsy — Sun, 21 Jun 2009 00:10:11 +0000

Surround Sound has its beginnings in the movies. Surround Sound was an essential way of drawing audiences into the world of cinema. In addition to the screen images, the dialog, the feeling of ‘being there” through sound effects, and the music that embraces audiences have been combined to create a thoroughly enjoyable cinematic experience.
Dolby Laboratories has contributed significantly to movie sound development. Its first major development was Dolby Stereo, followed in 1982 by Dolby Surround for the consumer market. Improvements in this technology led to the development of Dolby SR (Spectra Recording), which was introduced for consumers in the form of Dolby Surround Pro Logic in 1987.

The primary difference between the consumer formats of Dolby Surround and of Dolby Surround Pro Logic is that Dolby Surround uses three channels (Left, Right and Surround), while Pro Logic uses four channels (Left, Right, Surround and Centre). With the addition of the Centre channel, the distribution of sound elements becomes clearer In addition, by installing the adaptive matrix circuit into the playback side, Pro Logic emphasises the sound directions.

Dolby Pro Logic is a totally analogue format, the advantages are a Pro Logic amp can take the stereo sound from any stereo input and decode the pro logic encoding in the stereo sound track. Pro Logic has since been superseded by Dolby Digital, a superior sound format that is mainly found on DVDs, fortunately nearly all Dolby Digital amps are backward compatible with Pro Logic and therefore your VCR and TVs sound output.

Apart from the superior sound quality you will find on Dolby Digital the main difference you will notice is the need to connect a digital cable from you DVD player to your Dolby Digital amp. Pro Logic didn’t need this extra cable as being an analogue format the surround audio was matrixed on top of the standard left and right audio channels.

What is THX

Wattsy — Sat, 07 Jun 2008 00:52:14 +0000

THX sound is like a quality standard proposed by Lucas Film for the optimal playback system of sound effects in either the film studio or the dubbing studio and the theatre. In other words, with this system the sound track devised by a filmmaker can be played back in any theatre with a certain consistent level of quality maintained.

THX is the standard for the sound track, not for the sound formats as with Dolby Digital and DTS. Therefore, the two standards can be used simultaneously. If THX films recorded using Dolby Digital or DTS are played back with a Dolby Digital or DTS amp that uses the THX system, the result is even better sound effects. So in essence THX is more of a quality assurence program rather than a sound system.

The consumer format THX system incorporates the various techniques used in the theatre system so users can enjoy the full cinematic experience in their own home.

History of THX
The first movies were silent, with “talkies” introduced later. Cinemascope and stereo sound effects were subsequently developed, followed by the Dolby system featuring Surround Sound. Unfortunately, the sound systems of movie theatres lagged far behind those of these technologically advanced sound systems.

Lucas Film created a wonderful sound mix in the film “Return of the Jedi’ (of the Star Wars series). When the film was tested in an ordinary movie theatre, however, there were some sounds that could not be heard in the theatre but were audible in the dubbing studio. In order to make such sounds audible in the theatre setting as well, THX was developed. The name ‘THX’ comes from George Lucas’ film ‘THX 11 38′ and the X-over (cross over or crossover frequency filter) of the THX filter developer, Tomlinson Holman.


Onkyo 7.1 Home Theater

Configuration of THX
The THX Sound System has a variety of regulations involving the recording studios, playback equipment, theatres’ sound system and acoustic conditions, and other factors. Inspections to ensure compliance with these regulations are carried out every 6 months. However, at home, using only the THX processor and speakers for THX, you can enjoy the impact of THX sound. The THX system for home use is designed to be unaffected by the room’s acoustical characteristics.

What is DTS

Wattsy — Fri, 06 Jun 2008 08:30:03 +0000

Developed by the Digital Theatre Systems Company, DTS was developed for theatre use to play back digitally recorded signals . The digital sound track is recorded not on the film, but is recorded separately on a CD-ROM. A time code is recorded on the film to make playback of sound and image completely automated and in sync. Today DTS amps are affordable for home use with many DVD recorded in DTS as well as the competing Dolby Digital.


	Yamaha 7.1-Channel Home Theater Receiver

Introduced in the movie ‘Jurassic Park’ in 1993, DTS features superior sound quality and reliability, and has expanded to general consumer use.

Consumer-format DTS is basically the same as that for theatre use, but the soundtrack is provided as part of the CD, LD or DVD, A DTS disk looks no different to any other disk. DTS and DTSes is currently the premium format for sound reproduction far superior than Pro-Logic and also slightly better than Dolby Digital.

DTS-ES (Extended Surround) is a newer version of the DTS format, it adds an extra speaker to the rear of your home theatre setup. Called a 6.1 setup it is compatible with the existing 5.1 media. Two variants of DTS-ES exist, one is known as DTS-ES Matrix as it gets the sound for the 6th speaker by matrixing the two rear speakers creating a rear centre speaker channel, While the other version is known as DTS-ES Discrete as it contains a complete 6th channel for the rear centre speaker.

DTS was expanded yet again around the time Blu Ray and HD DVD hit the market, now in a 7.1 format know as DTS-HD Master Audio and DTS-HD High Resolution Audio. The Master Audio version can be described as a lossless audio format where every part of the original studio recording can be reproduced in your home bit for bit. The High Resolution Audio version is not as perfect as the Master Audio version but your ears probably wont pick it. It is often used on Blu-Ray discs where space is limited to fit the Master Audio version. A DTS-HD amp will be compatible with both versions.

What is Surround Sound

Wattsy — Thu, 05 Jun 2008 12:59:56 +0000

In the early days of film making, movies were made with images only, no sound. In 1927, however, a new era was entered with the movie “Jazz Singer’, in which sound was introduced. This was the first step in theatre sound-effects technology, one that has led to major developments in the industry. Movie sound technology began with monaural sound and has evolved to include stereophonic and Surround Sound.


	Sony STRDG720 7.1 Audio Video Receiver

Now, there are a number of advanced technologies that significantly improve audio performance in movie theatres. These advanced technologies include Dolby Digital, DTS, and the THX system. As with most of the technology that was first seen in theatres, high tech surround audio systems can now also be enjoyed at home. There are a few formats on the market now that have developed as time goes on so in this series we are going to take a look at various surround sound technologies.

In a movie theatre viewed from above, you would find the speakers are arranged so as to surround the audience. Speakers are placed In front of the screen along the walls to the left and right of the audience and to the rear.

By contrast, at home it is not easy to arrange the same equipment in the same position as in the theatre because of differences in room size and layout as well as acoustical problems. The most popular layout is the 5.1 layout that usually consists of left and right front, centre, and 2 surround speakers normally placed near the rear. Hence the 5 for the 5 audio channels in the room, the point 1 actualy refers to the Low Frequency Effect (LFE) speaker also known as a subwoofer. Dolby Pro Logic II was the first system to use this format, the earlier Pro Logic system was known as a 4.0 system despite having 5 speakers as the rear surround were mono and it also lacked a subwoofer.

Dolby Pro-Logic was the first major step forward in home theatre systems it encodes a centre and rear channel in the existing analog audio tracks, a good effect could be achieved with a pro-logic amp. Today’s Dolby Digital and DTS systems use a totally digital signal to achieve 5.1 channels and are far superior.

All six speakers are controlled independently in the Dolby Digital and the DTS sound systems as apposed to the earlier analogue Pro Logic systems. There are even extensions to the two competing formats that see even more speakers added to your lounge room with 6.1 and 7.1 systems.

Most amps sold today are backward compatible, therefore if you purchase a DTS amp you will be able to play Dolby Digital and Pro-Logic signals as well as the DTS signals. In order to get the benefit of a Dolby Digital or DTS amp you will need a digital cable ran from your audio source, your CD or DVD play may have a single plug on the back labeled digital out or SPDIF next to the standard left and right cable. you will need to run this to you amp to benefit from digital surround sound. A Pro Logic system lacks this connection as it is a totally analogue system decoding the 5 channels from the left and right channels. With a digital surround system digital audio is fed from your DVD into your amp where it is processed into the separate channels.