Home Cinema Systems

Home Cinema Systems Buyers Guide

For many people, the ability to recreate the sophisticated digital surround sound found in today's cinemas in the comfort of their own home is one of the major attractions of Home Cinema Systems.

The Main Components

There are a number of principal components required. These include the sound source which may be a DVD Player or DVD Recorder; a Set Top Box or a Freeview Box. The system will also include a surround sound processor which decodes the digital sound from the source and a set of 5 or more loudspeakers around the room together with a subwoofer for room shaking bass reproduction and depth.

How Does Surround Sound Work?

Most Home Cinema Systems use five channels of sound, and therefore need 5 loudspeakers. Upcoming systems may use 7 or even 9 sound channels. The positioning of these speakers is critical to ensure the best possible effect and is described in detail in the manufacturers' installation instructions. Essentially, you will need two main or front speakers either side of the screen (which often double as the stereo speakers when listening to music and are usually therefore larger and of higher quality than those used for the other channels), a centre speaker above or below the screen which handles most of the vocal sound and rear speakers situated behind the seating position to the right and left.

A further channel is used to drive the subwoofer. This handles deep bass and rumbling sounds. Although optional, a subwoofer will make a significant difference to the effect, particularly when watching movies with high action or special effect content. Subwoofers are necessarily large and heavy units, usually with a 10 or 12 inch speaker driver (or two!) in them but this is not generally an issue as they can be sited anywhere in the room - the human ear is not capable of identifying the specific location of low frequency sound sources, particularly when the other channels are in operation.

The surround sound processor (sometimes referred to as the AV receiver) decodes the audio signal from your DVD player or digital TV box. It then allocates and amplifies the output to the relevant channels and speakers. In some higher end systems, the amplification may be handled by a separate power amplifier or set of power amplifiers.

Audio Signals and Sound Formats

There are a number of different audio signals that can be used by the processor in creating surround sound.

The most basic of these is traditional stereo output, from which the AV receiver can emulate surround sound through the use of Dolby Pro Logic or Dolby Pro Logic II decoding. Although this can produce surround sound from any analogue stereo signal, it works best on material that was originally meant to be heard in a surround format such as movies.

The latest digital surround sound formats deliver higher quality results. These are the original surround sound signals from the film studios encoded into a single digital signal. This is then decoded by the AV receiver at home and the output sent to the relevant channels and speakers. Most modern films and an increasing number of digital television channels use five main channels and an additional channel for the subwoofer. They are therefore referred to as 5.1 soundtracks. 7.1 systems are also starting to appear. These use the same left right and centre speakers at the front, but replace the rear left and rights with two at the side and a another two at the back wall.

There are a number of different ways in which 5.1 soundtracks can be encoded. The most popular of these are Dolby Digital and DTS, the former being standard on nearly every DVD movie and on some Sky+ TV broadcasts. DTS is less heavily compressed than Dolby Digital and may sound slightly better. It is sometimes present as an optional soundtrack on DVDs. Most Home Cinema Systems can decode both Dolby Digital and DTS. Dolby's 7.1 is called Surround EX with 7.1 DTS referred to as DTS-ES. Again, these can be found as options on some DVD movies, and you'll need a compatible processor or AV receiver to decode the extra channels. Happily, 7.1 DVDs are also compatible with 5.1 systems.

Surround Sound Processor Considerations

Processors take the audio signals from your DVD player or other source and decode them into surround sound, allocating this to the appropriate channels. Most Home Cinema Systems have integrated amplification which powers each of the channels separately. Many also offer digital or optical outputs to allow the sound to be amplified externally via higher end 'separates' systems. Prices vary widely from £150 to many thousands of pounds. As you would expect, the more you spend, the more you get in terms of functionality; sound formats; upgradeability; output volume and quality. Ideally you should look for a processor that supports both Dolby Digital and DTS. If you plan to have a 7.1 channel system, you need to ensure that the processor is also capable of decoding Surround EX and DTS-EX soundtracks. If you are a true music buff, you may decide to take the traditional 'best of breed' approach and to purchase the processor, pre-amplification and power amplification separately to further improve sound quality and upgradeability.