Home Theater Surround Sound Processors. They have the place surrounded!
Surround processors are the part of a receiver or dedicated audio component that provides processing of Home Theater audio formats in a hi-fi system. Processing has come a long way. There are lots of different formats and standards that can be processed by a receiver, not all of them good.
Back in the old days when the world was in stereo, the equivalent to processing at that time was simply the world of the studio engineers mixing sounds into one of two channels. These stereo audio signals were recorded and designed to play back in one of two channels, left or right. No processing was necessary at the pre-amplifier stage as separation was assigned during the recording. Today you have discreet multi-channel encoding so that processes at the playback are required to decode exactly what channel which sounds should come from, up to as many as eight.
It's infinitely more complex for Home Theater surround applications, but for music good old fashioned stereo is still king. An overwhelming majority of music even when recoded digitally is recorded in two channel stereo. Granted there are processes designed to liven up a stereo recording, but these effects are largely superfluous and don't add anything necessary to the sound quality.
The newest of these effects is Dolby Pro-Logic II which has become a standard on Home Theater receivers. Dolby PLII allows the listener to tailor the sound to add a bit of depth. Dolby PLII recruits the rear speakers to play back certain frequencies in a time delay with the rest of the speakers to add the illusion of an acoustic field of depth. Digital signal processors (DSP) settings are meant to mimic equalizer presets- acoustic settings on many receivers that allow you to set your sound to "Church" or "Hall." Usually DSP settings add a tremendous amount of echo.
Audio purists shun these effects as cheesy, robbing the recoding of fidelity. They would tell you that you should try to play back the recording in the way that it was meant to be heard. But most people find effects like Dolby PLII or DSP pre-sets a fun toy used for amusement while playing with buttons. At best they might compensate for some environmental shortcoming in your audio room.
Popular Home Theater processes include:
- Dolby Digital
- Dolby Digital EX
- DTS ES
- DTS EX
- THX EX
- Dolby Pro-Logic
- Dolby Pro-Logic II
- Dolby Surround
High end surround processors like Sunfire's Theater Grand units look like full featured receivers, but they have no built in amplification. These are designed for true audiophiles who want to provide amplification and processing only from dedicated boxes engineered to perform these functions to the best of their ability. By using dedicated boxes, manufacturers of signal processors are free to build however they choose. The constraints of saving room for amplifications and all the errant side effects that might entail are not constraints.
Most Home Theater receivers that do it all in one box offer the flexibility of pre-ins and main-outs. This means the unit can be used as a dedicated processor without using its amps at all or conversely, it can be used as a multi-channel amp without using any of its signal processing capabilities. Using pre-ins/main-outs on a receiver might be a way to upgrade a system to a separates, perhaps by buying a dedicated signal processor or amp one at a time and using the receiver to fill in space.