Surround Sound Technology

Before purchasing a surround sound system, it is important to understand the basics of surround sound technology. Dolby Surround, Dolby Pro Logic, Dolby Digital (AC-3) and DTS Digital Sound are four of the most common formats in existence today. There are also two relatively new formats Dolby Pro Logic II and DTS Extended Surround. Today's movies are encoded with one or more of these formats, so in order to enjoy these technologies your surround sound system must be properly equipped. To make certain our clients have superb sounding systems, we've selected a surround sound product line that is compatible with the best of these formats.

Debuting in the 1970's, Dolby Surround is the oldest of all formats. Dolby Surround technology works by combining four audio channels into two channels for storage on videotape, laserdisc or for television. When videotapes or laserdiscs are played on a two channel stereo system they sound like a typical stereo set-up. However, when used with a four-channel system, they are decoded into left, center, right and surround loudspeakers, resulting in the listener being "surrounded" by sound.

Dolby Pro Logic builds on the Dolby Surround sound technology by providing greater distinction in the sounds heard from each channel and better relationships between sounds and on-screen action.

Dolby Digital (AC-3) is a digital format that was first released in 1997 and is compatible with only digital source components such as DVD (VHS is not compatible). To improve on Dolby Surround and Pro Logic, Dolby Digital offers six separate audio channels, which no mix in signals. The format is also called a 5.1 channel format, which means there are 5 discrete, full-bandwidth channels plus a low frequency effects (LFE) channel, for a total of six channels. This technology allows for complete distinction of sounds and the ability to direct sounds to different speakers (i.e. helicopters in the back left speaker). Additionally, Dolby Digital allows for greater low-frequency sounds via a subwoofer, enhancing the impact of high-action films.

THX Surround EX is the joint creation of Lucasfilm THX and Dolby Laboratories. This technology, which premiered in 1999, is an extension of the 5.1 channel format and enhances Dolby and DTs formats. THX Surround EX works by adding two rear mono surround speakers that enhance the performance of the surround speakers on the left and right. Additionally, it offers additional precision and distinction in sounds as well as the perception that sounds move from one area of the room to another. There are two types of THX compatible systems, the THX Ultra 2 for larger theaters and THX Select for smaller theaters.

Digital Theater Systems (DTs) is a competing format of Dolby Digital. The DTs format is also a 5.1 channel format but can be used in a 7.1 or 6.1 channel format, which means that one or two additional speakers are added to the surround sound system.

Dolby Pro Logic II is the newest innovation in Dolby Surround technology offering improved spatiality and directionality on Dolby Surround program material. The technology helps provide a convincing three-dimensional sound experience on conventional stereo music recordings versus the typical two-dimensional experience.

DTs Extended Surround is the new 6.1 channel surround sound format from DTs This format extends the 5.1 channel surround sound format with one (or two) back surround channels (speakers located in the back of the audience). There are two versions of this format DTs Extended Surround Matrix and DTs Extended Surround Discrete 6.1.

DTS-ES Matrix is a 5.1-channel format with a back surround audio channel that is not discrete - so in other words, it is not a true 6.1 format. This format is compatible with THX Surround EX equipment.

DTS-ES Discrete 6.1 is a true 6.1-channel format given the discrete back surround audio channel. This format offers better spatialization over the surround channels for complete 360-degree sound localization and surround pans (i.e., movement of sound in the surround channels from one side to another).