FAQ

Why Surround?
Surround sound was originally developed for theaters to give audiences a more realistic audio experience to go with big screen picture. Today surround sound is widely available for home theaters, and is quickly becoming available in automobiles. The advantage of surround sound over stereo is that it literally puts listeners in the middle of the performance, and provides a more compelling listening experience.

What are the different types of surround sound encoding?
Surround sound can be encoded in either discrete (individual) or matrix (combined) track formats. The two most common discrete encoding formats are Dolby Digital and DTS, which are used in both theaters and on DVDs. Sony has abandoned the SDDS format. Matrix surround encoders are manufactured by SRS Labs (Circle Surround) and Dolby Laboratories (Pro Logic and Pro Logic II).

What are the different types of surround sound decoding?
Professional discrete surround decoders are manufactured by Dolby and DT for theatrical and DVD playback. Professional matrix surround decoders are manufactured by Dolby (Pro Logic and Pro Logic II) and SRS Labs (Circle Surround). Consumer matrix surround decoders are licensed by Dolby (Pro Logic and Pro Logic II), DTS (Neo 6), Harmon (Logic 7), and SRS Labs (Circle Surround and Circle Surround II).

What is the difference between discrete and matrix surround?
Discrete surround consists of individual tracks that are recorded, stored, and transmitted separately. Discrete playback decoders route the individual tracks directly to the corresponding speakers. Matrix surround takes individual tracks and encodes them into a two channel Lt/Rt for storage and delivery. Matrix surround will playback in stereo without decoding, but when routed through a decoder the two encoded tracks will unwrap and the individual channels will playback in surround on the corresponding speakers.

Won't all consumer matrix decoders create surround?
Yes, all consumer matrix decoders will do a "blind up-mix" and create a pseudosurround experience. In fact, the SRS Circle Surround II consumer decoder utilizes patented "multi-bandwidth steering" to create a very compelling surround experience. However, blind up-mixes are program material dependent, and often only create 5-channel mono with the LFE derived from bass management. The best results for consumer matrix decoders come from program material that is Lt/Rt encoded.

Who manufactures matrix surround encoders?
SRS Labs (Circle Surround) and Dolby Laboratories (Pro Logic and Pro Logic II) are the two companies who currently have matrix encoders available. Circle Surround can encode and decode 4.0 (LCRS), 5.1 and 6.1 surround. Pro Logic is a 4.0 (LCRS) format only, and Pro Logic II is a 5.0 format only that uses bass management to create the LFE .1 channel. Neural Audio has developed a 5.1 matrix watermark encoder, specifically for radio broadcast, and Telos has developed a 5.1 parametric surround encoder, also for radio. As of the summer of 2005, neither Neural or Telos have consumer decoders available.

What is the difference between 5.1 discrete and Circle Surround 5.1?
5.1 discrete tracks are always recorded, stored and transmitted individually. This is acknowledged to be the superior format when available. However, radio and standard definition (SD) television cannot broadcast discrete audio channels due to bandwidth limitations. This is where Circle Surround provides an excellent high quality alternative. Circle Surround is an advanced matrix encoding system that uses highly sophisticated Digital Signal Processing (DSP) to encode six individual tracks into a two channel Lt/Rt. During playback those two channels will expand back to the maximum amount of channels available when routed through a surround decoder. Listeners will hear 5.1, or even 6.1, surround sound that is very close to the original discrete tracks. If the two Lt/Rt channels are not routed through a surround decoder, listeners will still hear high quality playback in stereo or even mono.

What is an Lt/Rt?
Lt/Rt stands for Left total/Right total. It is the sum of matrix surround information encoded in the Left and Right channels.

Isn't an Lt/Rt only 4-channels?
No. The original Lt/Rt developed by Dolby and still in use today for some analog optical film tracks and broadcasting, Is comprised of 4-channels, known as LCRS. This 4.0 Lt/Rt does not have a LFE/Subwoofer channel, and the mono Surround channel is bandwidth limited at 7 kHz. SRS developed an advanced matrix Lt/Rt called Circle Surround that can encode 5.1 or even 6.1 channels with full bandwidth stereo surrounds. Dolby then introduced Pro Logic II 5.0 encoding with stereo surrounds, with the LFE channel derived from bass management. Many industry professionals do not realize that an Lt/Rt is no longer limited to 4-channels.