The different kinds of home theater surround sound systems can be categorized by factors such as how many sound channels they have, the formats they use, and whether they are assembled from components or acquired as a package. Traditional surround sound systems technically need to have at least five channels, though they often make use of many more. The total number of channels is typically shown by a whole number that represents how many front, rear, right, and left channels there are, followed with a decimal point and another number, which indicates the presence of a Low Frequency Effects (LFE) channel. Many different formats are used as well, which use various digital compression methods or lossless audio to create a surround sound experience. High end home theater surround sound systems can typically be assembled piece by piece, while many lower cost setups are purchased in the form of a home theater in a box.
One of the most common ways that home theater surround sound systems can be differentiated is the number of sound channels they have. The number of channels found in these systems begins at five and goes up from there, as new setups with additional channels are constantly under development. One popular type of surround sound system is named 5.1, which indicates that it has a center channel, two front and two rear channels and a LFE channel. A 6.1 system adds a rear channel, 7.1 has two rear channels and 9.1 typically adds additional height channels.
Another way to differentiate home theater surround sound systems is the methods they use to deal with different channels. This is typically done in three main ways. Discrete channels contain sound information that is completely separate from the other channels. Matrixed sound recovers audio data for two or more speakers from a single channel. An example is one channel that contains information for both the center speaker and the LFE channel. The third type is lossless audio, which takes up a lot of storage space, but can allow for a higher quality of sound reproduction.
Home theater surround sound systems also use a number of different digital compression methods. Some of these methods use discrete channels, while others are matrixed. The formats that a surround sound system is capable of playing are determined by the receiver or processor. Some of these units can handle multiple formats, while others also include digital signal processing (DSP) or other additional settings. DSP formats are usually specific to each manufacturer, and are designed to create a virtual soundstage that can simulate a listening experience in a music hall, rock arena, or other venue.