Though my web site primarily emphasizes matrix surround sound systems, there are many other types of surround systems. What follows, is a quick overview of some of the other implementations of surround sound currently available.

Dolby Surround
Plain "Dolby Surround" is much like matrix surround. There are some key differences however. Dolby Surround limits the frequency response of the rear speakers. Frequencies above 7 kHz are suppressed in order to reduce front-to-back channel leakage of upper octave information. (It is debatable as to whether or not this frequency suppression is really needed or desirable.) Also, Dolby Surround delays the audio signal sent to the rear speakers. (Typically by about 20 milliseconds.) This allows your brain to better lock on to the sounds that should be primarily coming from the front speakers. Much more information can be found by reviewing Dolby's own web site.

Dolby Pro-logic
Dolby Pro-logic has two basic enhancements over regular Dolby Surround. First, a front center channel is added providing 3 distinct front sound sources (left, center, and right). This is very beneficial when watching a TV program or movie as the dialog will come from where the screen is located for all listeners--even those off center from the listening area. Secondly, "steering logic" is added. This "steering logic" can dynamically adjust the volume of any one channel at a time. Thus the separation between channels is significantly enhanced. Note, however, that this steering logic can possibly cause problems when listening to music-only or other non-Dolby Surround sound material. If you have a "Pro-Logic" receiver and are listening to any stereo source that is not specifically encoded in Dolby Surround, you may wish to set your surround decoder to a mode other than the Pro-Logic setting. Do this if the music or sound seems to unnaturally bounce around from one channel to another. As mention in the paragraph above, Dolby has an excellent web site covering much of their technological innovations. Dolby's home page is at: www.dolby.com.

Dolby Digital
This surround sound technology is incompatible with regular stereo source material. That is, it requires a digital data stream specially formatted using Dolby's AC-3 (5.1 channel) surround format. Currently Dolby Digital can be found in HDTV (High Definition Television), DVD (Digital Video Disks), and in some DSS (Digital Satellite) systems. Many new stereo receivers now incorporate Dolby Digital decoders. Because of its use in DVD and HDTV, Dolby Digital has a bright future.

Dolby Digital provides 5 full range discrete channels along with a "bass effects" sub-woofer channel. It's the current state-of-the-art standard in movie surround sound. If you are going to be buying a new stereo receiver within the next few years, get one with Dolby Digital. (Receivers with Dolby Digital technology also include Dolby Pro-Logic and often include one or more basic surround sound modes.)

Virtual Surround Sound Technologies
A number of different technologies and companies (including Dolby) are trying to bring surround sound to those who are unwilling or unable to incorporate additional (more than two) speakers for their listening environment. Virtual surround is becoming especially popular with home computer users who do not wish to attempt setting up rear speakers at their computer station.

Virtual surround can work surprisingly well albeit with several (severe) limitations. Generally, the "sweet spot" (where you will experience the surround effect) is very, very, small. Usually, only one person in the room can be seated properly to hear the correct surround effect. Also, if you turn your head, that is, look away from the front of the soundstage, the surround effect is lost or, at the very least, the perspective of the sound sources will be incorrect. Finally, rear surround effects are often not very convincing. However, with movies and video game material, where a visual image supplements the surround experience, virtual surround can be quite impressive.

Besides for Dolby, some of the other virtual surround technologies include:

Qsound
QSound is one such company that provides a virtual surround sound "solution". I personally have had experience with using QSound as it is incorporated into a computer game I own called OutWars. The surround effect is quite effective.

SRS (Sound Retrieval System)
Probably one of the first implementations of stereo enhancement came from Hughes Aerospace when they developed the Sound Retrieval System. Better known by its acronymn, SRS. The original intent of SRS was to provide headphone listeners (on airlines) a more realistic sound experience when watching in-flight movies. To the best of my knowledge, it never got used for that purpose. It did develop somewhat of a "cult following" as a stereo and mono enhancement technique. (Separate processors were available in the late 80's/early 90's.) SRS is currently implemented in a number of different products. Sony TVs were the first to offer SRS, but now it is available on some PCs, receivers, and various other audio gadgets.

Binaural recordings
If you are unfamiliar with binaural listening, think of it as "surround sound for headphones". Binaural recordings usually are made with two microphones placed on the side of a dummy's head. The microphones are placed at approximately the same location as where the ears would be. In theory, making such a recording, then playing it back thru headphones, should provide a very realistic sound field. Essentially placing you at the original recording!

Now I have had very little exposure to binaural recordings. The few recordings I have heard, have not overly impressed me when using headphones. However, I have had excellent results when playing binaural recordings thru a matrix surround system! The soundfield is very clean and natural with excellent imaging.

A great source of information of binaural audio can be found at the FAQ site:  Binaural for Beginners (FAQ).

Ambisonics
A close "cousin" of matrix surround sound is ambisonics. Though never very commercially successful, ambisonics has some very avid promoters. I've never personally experienced any ambisonic reproduction but you may be interested in learning more about it. A great starting place is www.ambisonic.net.

Getting Back to the Music
One of the main points I hope to get across (on this web site) is that surround sound is great for music. Most stereo recordings, which are recorded live or rely on ambient sound (such as concert recordings), benefit significantly from surround sound playback. However, there have been a considerable number of recordings made with surround sound specifically in mind.

Several CDs have been made utilizing Dolby Surround. However, I have yet to be impressed with many CD recordings carrying the Dolby Surround logo. On the other hand, most CDs of the Nimbus label are recorded using a technique known as UHJ Ambisonics. The surround effect I've obtained from playing back such ambisonic recordings have been consistently good.

This web page was last updated on: 01/25/20 12:13 PM Pacific Time.