Surround Sound

Surround sound has become a popular feature in some of todays most common consumer video electronics. This is primarily due to the popularity and desire to reproduce the theatre experience at home. There are several different types surround formats (multi-channel sound derived from two-channel sources) and discrete surround formats (multi-channel sound transferred as discrete channels).

The surround sound formats (Dolby* Pro Logic*, various DSP modes, etc.) convert a stereo (two channel) signal to three or more channels. Sound is taken from two channels (stereo) and by using special processing (and possibly a specially encoded stereo signal), it is converted to a multi-channel, enveloping super cool sound field.

Although various types of "surround sound" can be derived from surround technologies, there is also discrete surround. Discrete surround technologies (Dolby Digital, DTS, etc.) create a significantly better surround sound experience, because each speaker has its own discrete channel (discrete surround formats typically require either a digital connection or a 5.1 channel analogue connection). For example, Dolby Pro Logic can take a stereo (two-channel) input and generate information for two additional channels (the centre channel for the dialogue and the single surround channel for surround effects), making a total of four channels. Dolby Digital 5.1, on the other hand, has five discrete channels (front left, front right, centre, surround left and surround right), plus a partial channel (the .1 in 5.1) for LFE (low frequency effects, or low bass) for a subwoofer. This results in significantly increased channel separation and a more realistic surround experience. As for the specific differences between Dolby Digital and DTs (and the various forms of these technologies), please refer to their respective websites for more information.

There have been tremendous advances in formats very recently with DTs Neo 6 and Dolby Pro Logic II, which come closer than ever before to matching the performance of discrete surround formats. For stereo only sources, most DSS channels, VCRs etc., these technologies significantly improve the surround performance when compared to other surround formats. However, if you have the option between a discrete surround format (Dolby Digital, DTs, etc.) and a surround format (Dolby Pro Logic, DSP modes, etc.), discrete formats will always create a more realistic surround sound experience.

* "Dolby", "Pro Logic" and the double-D symbol are registered trademarks of Dolby Laboratories.