Sound technology has come a long way in advancing home theater systems. You get the feel of being at the cinema in your own living room. At this time you can choose from surround sound, Dolby Prologic(r), Dolby Digital(r), and THX(r).
Surround Sound was the first breakthrough in home theater technology. Dobly Surround(r) introduced it in 1982. The surround channel is decoded and then played back just as it was recorded in the movie's sound studio.
Dolby Pro Logic(r) came next in 1987. This made decoding an active center channel to its own speaker possible. This made the dialogue clearer and allowed the left and right front speakers to be spaced further apart, giving a richer sound distribution.
In simple terms this technology decodes and converts two channel stereo audio from your VCR, DVD or TV into four channels of audio (by going to your surround speakers) - giving your current system the quality it needs for a true home theater experience.
Dolby Digital(r) is the newest surround sound technology. It provides six discrete channels with a full range of sound. The six channels are front center, front left, front right, rear left, rear right, and the bass or subwoofer. This technology allows more decoding options to allow a choice of playing in mono, stereo, Dolby Surround or Pro Logic, or all 6 channels.
You will still need the Dolby Pro Logic decoder to use this new Dolby Digital technology. There is still an abundance of material that uses the traditional two channel stereo sound, which only Dolby Pro Logic can separate into four for fuller surround sound. The Dolby Digital decoder has the Pro Logic decoder built in, so you will not need separate decoders if you get Dolby Digital. If you plan to purchase a DVD Player or HDTV (High Definition Television), you will want to choose the Dolby Digital because it is the closest to the sound and feel of a real movie theatre.
THX(r) sounds like a brand name, but it is actually a licensing technology for home theatre equipment. It ensures the highest standards on the reproduction of theatre-type sound. THX has become a five star standard in acoustic and speaker placement while certifying the equipment that is able to produce the best sound. Dolby and THX often work together when creating new high quality home theatre equipment.
With THX's patent, sound that was created for the movie screen can now be heard in your own living room on a home theatre system. You know you will be getting the real thing if the equipment is THX certified.
THX audio systems are pricey, but have clearer dialogue, easy bass reproduction (great for action movies with lots of explosions), enveloping surround sound and wide frequency ranges.