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Guide to surround formats

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cyrus

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Guide to surround formats

Stereo took off in the '60s, and the first surround format to take hold and flourish was Dolby Surround in 1982. Dolby Surround is a matrix format; that is, its surround effects are encoded in two stereo channels. Many of today's surround formats are discrete and feature six separate tracks.

Some DVDs feature multiple surround formats--for example, Dolby Surround, Dolby Digital, and DTS--on a single disc. This brings up another angle to the surround story; to enjoy the full sound potential of, say, a DTS-ES-encoded DVD, you need a receiver that processes DTS-ES. In other words, formats exist in both software and hardware. Other formats, such as Dolby Pro Logic II and DTS Neo:6, are found only on hardware--receivers, HTIBs, DVD players, and so on--and are applied to processing software or music sources, such as CDs, DVDs, MP3 files, and radio.

When we designate the maximum number of speakers/channels for each format, such as 5.1 or 6.1, we're referring to the number of front, center, rear, and possibly center-rear speakers (the .1 refers to the subwoofer) that the format can use. Stereo, a.k.a. 2.0, is a two-channel format. Check out the diagram below to see how they are set up in a room. Note that even though 7.1 systems use two back-surround speakers, the same channel of information goes to both of them.

speakers.gif

Dolby Formats

Dolby Digital
Maximum number of speakers/channels: 5.1

Upside: Dolby Digital is the near-universal surround format.
Downside: Sound quality, while acceptable for movies, is a far cry from ultrahigh-resolution formats such as DVD-Audio and Super Audio CD (SACD).
Forecast: It is, and will likely remain, the preeminent surround format.

Dolby Digital is the most popular surround format and can be found on virtually every DVD, including almost all DVD music discs, and many HDTV programs. Pretty much every A/V receiver and HTIB on the market features Dolby Digital processing.

Dolby Pro Logic II
Maximum number of speakers/channels: 5.1

Upside: Pro Logic II can be found on most new receivers and HTIBs.
Downside: None.
Forecast: This very popular format is in for the long haul.

First, Pro Logic II isn't one of those synthetic "jazz club" and "stadium" modes and doesn't add synthesized reverberation or echoes. It's a hardware-based format that's compatible with all stereo and matrix-encoded surround software. Pro Logic II is an update of the original Pro Logic and can be used to freshen up Dolby Surround-encoded videotapes and DVDs. It also works wonders with stereo CDs and radio broadcasts.

Dolby Digital EX
Maximum number of speakers/channels: 7.1

Upside: Creates a more spacious and focused surround effect than 5.1 surround.
Downside: Scarce availability of EX-encoded DVDs; requires a Dolby EX receiver and additional speaker(s); difficult to implement in a room where the prime listening position is located near a wall.
Forecast: Because of EX's downsides, interest in the format will likely remain low.

Dolby EX is a 6.1-channel format, adding one (or two) rear center-surround channel speakers to the standard 5.1 array. EX can deliver more enveloping surround effects than standard Dolby Digital. EX processing can be used to improve the sound of regular Dolby Digital-encoded DVDs. Unlike DTS ES, Dolby EX features an extra rear channel that's matrix rather than discrete. That's why ES can provide a more precise location for the rear-effects soundstage.

Dolby Digital Plus
Maximum number of speakers/channels: 13.1

Upside: Improved surround sound performance with high data rates and increased audio channels; Backward compatible with existing Dolby Digital decoders.
Downside: Requires new HDMI/FireWire interface and additional speakers.
Forecast: Elected by the DVD forum, this latest product from Dolby Laboratory will be the standard feature for future High-Definition materials.

An extension of Dolby Digital (DD), the Dolby Digital Plus (DD+) has been chosen as the mandatory surround format for Blu-ray and HD-DVD. It supports up to 13.1 discreet channels with a maximum data rate of 6Mbps. To support the high data rate, HDMI and IEEE1394 (FireWire) have been selected as the new digital interface for DD+ connectivity. The latest Dolby format is backward compatible with existing DD decoders via down-mixing capability and SPDIF digital audio output. DD+ will be available from late 2005.
 

cyrus

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Guide to surround formats -DTS

DTS Formats

DTS
Maximum number of speakers/channels: 5.1

Upside: Some audiophiles feel that DTS-encoded DVDs offer better sound than those with Dolby Digital.
Downside: Compared to Dolby Digital, DTS encoding is found on relatively few DVDs.
Forecast: We'll see more and more DTS-encoded DVDs.

DTS is an alternative to standard Dolby Digital. DTS uses less compression than Dolby, and some audiophiles believe it produces richer bass and greater dynamics. Virtually all receivers and home-theater systems include DTS processing.

DTS Neo:6
Maximum number of speakers/channels: 7.1

Upside: Neo:6 provides up to six full-band channels of matrix decoding from stereo matrix material.
Downside: None.
Forecast: This format will last.

It's similar to Dolby Pro Logic II, but Neo:6 produces up to 6.1 channels of surround vs. PLII's max of 5.1. You can use two rear-center speakers and bring the speaker tally up to 7.1. Like its rival Dolby format, Neo:6 is fully compatible with all stereo sources.

DTS ES
Maximum number of speakers/channels: 7.1

Upside: More enveloping surround effects than standard 5.1 surround.
Downside: Requires a receiver with ES processing; difficult to implement in rooms where the prime listening position (couch or chair) is located near a wall; ES-encoded DVDs remain scarce.
Forecast: Because of these downsides, interest in ES will likely remain low.

ES adds one (or two) rear-center-surround channel speakers to the standard 5.1 array and can deliver more enveloping surround effects than standard Dolby or DTS. Unlike EX, Dolby's matrix, 6.1-channel format, DTS ES offers a fully discrete back channel for more precise localization and imaging. But that advantage over Dolby EX holds for only DTS ES-encoded DVDs; currently, a mere handful of titles is available. To utilize this format, you'll need an ES-capable receiver.

DTS HD
Maximum number of speakers/channels: Unlimited

Upside: Lossless format for the purist. Backward compatible with existing DTS decoders.
Downside: Optional surround sound format for Blu-ray and HD-DVD.
Forecast: Technically superior compared to its Dolby counterpart, DTS-HD will be a highly sought-after surround sound format for audiophiles.

DTS HD, previously know as DTS++, is DTS's answer to its rival surround sound format. It supports unlimited number of surround sound channels and delivers audio quality at bit rates extending from DTS digital surround to lossless. Although technically superior over its Dolby counterpart, DTS HD is selected only as an optional surround sound format for Blu-ray and HD-DVD. The new DTS format is backward compatible with existing DTS decoders and supports down-mixing function for converting DTS HD signal to 5.1 and stereo formats.

DTS 96/24
Maximum number of speakers/channels: 5.1

Upside: Comparable to DVD-Audio quality but doesn't require a DVD-Audio player; six discrete channels; full video capability; DTS 96/24 discs will play on any DVD player.
Downside: Limited software availability; requires receivers with DTS 96/24 processing.
Forecast: DTS 96/24 will coexist with DVD-A but won't likely become a mainstream format.

DTS 96/24 is similar to DVD-Audio in that it provides high-resolution 96/24 5.1-channel sound, but it also offers full-motion video capability (DVD-A has only limited video capacity). Another advantage is that you don't need to buy a new DVD-Audio player; the DTS 96/24 signal can be fed by any DVD player via a single digital cable to DTS processors in the receiver. To get the best sound, you need a receiver with up-to-the-minute DTS 96/24 processors.
 

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Guide to surround formats - DVD-Audio, SACD, and THX

DVD-Audio, SACD, and THX

DVD-Audio
Maximum number of speakers/channels: 5.1

Upside: Better sound quality than CD; discs usually have surround and stereo mixes; some titles contain multimedia capabilities, photo galleries, and occasional video.
Downside: Limited selection of titles currently available.
Forecast: Universal Super Audio CD/DVD-Audio/Video players will likely ensure the survival of this format.

DVD-A offers 1,000 times the resolution of CD and can deliver up to six channels of ultrahigh-resolution sound. But to access those tracks, you need a DVD-Audio player, although almost all DVD-A discs have lower-quality Dolby Digital or DTS tracks that can be played by any DVD player. DVD-Audio sound has great detail and texture, and it's more lifelike than CD. DVD-Audio will be primarily of interest to audiophile-inclined home-theater fans. To enjoy a DVD-A player's full sound potential, you must use a receiver equipped with 5.1-channel analog inputs and good-quality speakers.

Super Audio CD
Maximum number of speakers/channels: 5.1

Upside: Better sound quality than CDs; many SACD discs include multichannel and stereo mixes.
Downside: Limited selection of titles currently available; this is strictly an audio-only format and lacks video capability.
Forecast: Universal machines that play Super Audio CDs, DVD-Audio/Video discs, and CDs will eventually ensure the format's long-term survival.

The SACD format employs a new technology dubbed Direct Stream Digital (DSD). Proponents claim DSD is kinder and gentler to the music than CD's Pulse Code Modulation (PCM) format. While CDs poke along with a 44.1kHz sampling rate, DSD cranks things up to a warp-speed 2.8224MHz. This results in vastly greater resolution, texture, and detail than CDs. Standard Super Audio CDs will run on only SACD players, while newer hybrid SACDs will play on SACD, CD, and DVD players. To enjoy an SACD player's surround sound, you must use a receiver equipped with 5.1 analog inputs. A good-quality speaker system is required to appreciate the format's potential.

THX
Maximum number of speakers/channels: 7.1

Upside: THX-certified systems produce a more consistent, higher-quality home-theater experience.
Downside: Can be found on only expensive components.
Forecast: THX's systemic approach will ensure its long-term survival.

Not a surround format per se, THX strives to deliver cinema-quality picture and sound to home systems via certified products such as speakers, receivers, DVD players, and even cables. Two levels of certification are offered: Select and Ultra 2. Select components are optimized for use in midsized rooms of less than 2,000 cubic feet, and Ultra 2 components can accommodate 3,000-cubic-foot rooms. Also, Ultra 2 is a 7.1-channel system, capable of producing a more uniformly distributed surround effect throughout the room than Dolby EX or DTS ES surround.
 
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