For years I’ve kept up with all the sound formats. Here are a few examples of the sound formats from over the years: Hi-Fi, Dolby B and C, Dolby Pro Logic, Dolby Digital Surround, DTS, THX, Dolby Surround EX….the list goes on and on. Regardless of the number of formats and compression agents, this strange language has produced some of the most incredible breakthroughs in home theater sound. Yes, I am certainly guilty of cranking up my stereo for my neighbors and friends to show off my Dolby Digital, THX Certified System during a scene from the Star Wars Pod Race, Fifth Element and especially Twister….I’ve probably done this a couple thousand times in my life (be sure the spouse and kids are out of the house…don’t want to damage those fragile ears). There is nothing sweeter than hearing an airplane fly by from left to right and actually feeling the sense to duck! This is when sound is at its best, but the terminology is certainly getting out of hand as different companies are providing better and more realistic sound compression and re-creation. So, with that being said, I would like to provide a shopping list of definitions for all of you who have ever looked at the billboard of logos near the bottom of your Stereo Receiver or perhaps give you some insight into a future purchase. This list is a current collection of digital formats you may have seen from time to time and wondered about. The following list from HiFi-Ring.com does cover the current formats found on a majority of receivers today.

Surround Sound Formats

Dolby 3-D: Incoming technology expected to come within the next year.
Dolby Digital: (aka AC-3) Surround sound technology that delivers digital audio for up to 5.1 discrete channels (Left/Center/Right/Left surround/Right surround/Low-Frequency Effects) with full frequency response in all channels (3Hz — 20kHz).
Dolby Digital EX: (aka Dolby Digital Matrix 6.1) 6.1-channel surround sound format based on Dolby Digital including an additional rear center channel, matrixed into the rear channels.
Dolby Digital Live: Real-time encoding technology that brings surround sound to interactive audio, such as video gaming and PCs. This technology converts any multichannel audio signal to the Dolby Digital format and provides one-cable connectivity between a PC and home theater systems.
Dolby Digital Plus: (aka DD+ or E-AC-3) Surround sound format with eight full-range channels encoded up to 24-bit/96kHz per channel for a bit rate of 6.144 Mbit/s compared to 0.640 Mbit/s for Dolby Digital. This lossy audio compression scheme was developed specifically for HDTV and Blu-ray discs.
Dolby Headphone: Signal processing technology that delivers 5.1-channel surround sound over any stereo headphones.
Dolby Pro Logic: The foundation of the multichannel home theater experience. This technology is based on Dolby Surround and decodes audio sources encoded in two-channel such as videocassettes, DVDs and TV broadcasts, to four-channel playback (front left, front right with center and rear-mono matrixed channels).
Dolby Pro Logic II: Improved version of Dolby Pro Logic with a more intelligent matrix decoder which offers “bass management” as well as “width”, “dimension” and “panorama” controls. The Pro Logic II expands any two-channel source audio to a 5.1-channel full bandwidth playback (Left/Center/Right/Left surround/Right surround/Low-Frequency Effects).
Dolby Pro Logic IIx: Extension of Dolby Pro Logic II, this algorithm processes native stereo and 5.1-channel content to produce 6.1- or 7.1-channel playback with rear-mono.
Dolby True HD: Similar to DD+, the True HD was also developed for high-definition disc-based media. Including eight full-range channels (Left/Center/Right/Left surround/Right surround/Left back/Right back/Low-Frequency Effects), this lossless format delivers sound that is bit-for-bit identical to the studio master (24-bit/192kHz) through a single-cable digital connection for audio and video.
Dolby Virtual Speaker: Advanced signal processing technology that delivers 5.1-channel surround sound effects from just two speakers.
DTS Digital Surround: Surround sound technology similar to Dolby Digital that delivers digital audio for up to 5.1 discrete channels (Left/Center/Right/Left surround/Right surround/Low-Frequency Effects), but it can use higher bit-rate audio encoding which provides improved sound quality in theory.
DTS-ES Discrete 6.1: True 6.1-channel surround sound format where an additional surround back audio channel is discretely encoded into the DTS bit stream.
DTS-ES Matrix 6.1: Surround sound technology that delivers 5.1 discrete channels of standard DTS sound plus a sixth channel (matrixed into the left and right surround channels) of audio information to deliver 6.1-channel sound through one or two back surround speakers.
DTS Express: Previously known as DTS-HD Low Bit Rate, the DTS Express provides low bit rate audio coding for applications with 2- to 5.1-channel audio, focusing primarily on bandwidth constrained audio applications, such as Internet, broadcast audio, and secondary audio on next generation optical disc players. It’s currently used in picture-in-picture, director commentaries and other Blu-ray’s interactive features.
DTS-HD Master Audio: Previously known as DTS++ and DTS-HD, the DTS-HD MA supports up to eight discrete channels encoded in 24-bit/192kHz (Left/Center/Right/Left surround/Right surround/Left back/Right back/Low-Frequency Effects) and was developed especially for the new high-definition disc formats like Blu-ray and HD-DVD.
DTS-HD High Resolution Audio: Similar to the DTS-HD Master Audio, the HRA is encoded at 24-bit/96kHz per channel.
DTS Neo:6: Similar to Dolby Pro Logic II, the DTS neo:6 provides 6.1-channel matrixed surround sound from any stereo source.
DTS Surround Sensation: Down-converts DTS 5.1, 6.1, or 7.1 -channel soundtracks to stereo while processing a realistic simulation of surround sound for two-channel equipment such as headphones and 2.1-channel home theater systems.
THX Neural Surround: Technology that provides multi-channel surround sound (up to 7.1ch) encoded within a two-channel stereo format, developed especially for limited bandwidth such as digital audio,video games, video broadcasting and Internet streaming
THX Select: (Thomlison Holman eXperiment) Created by Lucasfilm, the THX select is a certification for speakers as well as DVD/Blu-ray players which requires a 7.1 speaker configuration with two back-surround speakers engineered and designed to complement a THX Select2 certified A/V receiver. These must be designed to deliver optimal quality audio and video presentations in small to medium-sized residential rooms (overall room volume of circa 2,000 cu. ft.).
THX Select2: Certification for 7.1-channel A/V receivers designed for small to medium-sized residential rooms (overall room volume of circa 2,000 cu. ft.).

You’ve probably noticed that in order to take advantage of the formats your receiver possesses, you need to have quite a few speakers…anywhere from 5 to 7 plus a subwoofer or two. Each of the speakers creates the discrete channels of sound and all together, recreate the sound experience digitally encoded on DVDs and Blu Rays. This is a lot of information to cover and some of this is in the moderate to upper technical range, but I think it provides a great grocery list of the current lingo.As we say at the School of Advanced Military Studies in Fort Leavenworth, KS….it has been my pleasure to “drop some knowledge” on the subject of surround sound formats!

Happy Listening!!!