System Building

Add Home Cinema To A Hi-Fi

You don't have to abandon your hi-fi to enjoy home cinema in your living room. This page guides you through the process of adding surround sound decoders and extra speakers to your hi-fi system to produce real home cinema that won't compramise your hi-fi sound.



Adding a home cinema to an existing hi-fi system is a simple, cost effective way to benefit from home cinema without interfering with the sound quality of the hi-fi itself. Adding home cinema to a hi-fi gives you superb surround sound, while maintaining the sound quality of your hi-fi. This is the way that I first entered the world of surround sound home cinema and have never been disappointed with the overall quality of performance, even when compared to a dedicated home cinema system based around an A/V Amplifier. This option is ideal if you value the quality of your hi-fi stereo but also want great surround sound.

Your hi-fi sound quality is likely to be reduced if you replace it with a dedicated home cinema amplifier. Adding a processor allows you to continue using the system you have now, while being able to enjoy surround sound whenever you want at the flick of a switch.

Below is a diagram showing how the new Home Cinema components fit into an existing hi-fi system:  
Add-on System Diagram

You may already have a number of the components shown above - a stereo hi-fi amplifier, two front speakers and probably a television close by. In order to add Home cinema, you need to connect some dedicated A/V hardware. Firstly, a video source, such as a video recorder (VCR), DVD player or satellite receiver, is needed.

When using the system to watch a movie or TV show with surround sound, the picture (video) information is fed directly from the source to the television, while the sound (audio) information is fed from the source to the hi-fi amplifier in the same way as you would connect a CD player or radio tuner.

The surround sound information, ie. the sound information for the rear surround and front centre speakers, is decoded in an external processor. This component is connected to the amplifier using the amplifier's tape loop. Within the processor will be a Dolby Pro-Logic decoder. The sound information from the source passes to the amplifier and then on to the processor through the tape loop. The surround sound information for the extra speakers is decoded in the processor to create four separate audio channels. The front left and front right audio channels are fed back along the tape loop and are amplified by the hi-fi amp, and heard through the existing hi-fi speakers. The audio information for the front centre and rear surround speakers is amplified by the processor itself and heard through additional speakers placed around the room (the extra speakers are connected directly to the processor). The processor may also have an output for the addition of a sub-woofer.

  Below is a diagram showing the most common positions for speakers:


3D Room Diagram



The system detailed so far on this page is based around adding a processor with a Dolby Pro-Logic decoder. If you intend to add a digital surround decoder at a later date, such as Dolby Digital, a bit of thought is needed before buying a processor.

You must ensure that the processor has a panel of phono plugs called a "six channel input" for the addition of a separate digital decoder. This gives you two options. You could add a source component such as a DVD player with a built-in Dolby Digital decoder and output the decoded audio channels from the DVD player directly into the six channel input. Alternatively, you could add a separate Dolby Digital decoder to the processor, and a source component simply reads and outputs a raw Dolby Digital data stream. The most likely source of Dolby Digital that you will use is a DVD player. These players are available either with or without their own decoder built-in, but all players can read a Dolby Digital soundtrack and output the data to a separate decoder, if required, using a digital cable.

The rule with digital surround sound is that a digital cable isused to carry sound data from the source to the digital decoder, and six separate cables are used to carry the separate decoded audio channels from the decoder to the amplification. This rule applies regardless of where the decoder is positioned within a system. When using an external decoder, the digital data from the DVD player is passed along a digital cable to the decoder. Once separated, the resulting audio channels are passed to the processor using six phono cables. The rule still applies to DVD players with a built-in decoder, except that the digital cable between the player's laser and the decoder is contained internally. The player is still connected to the processor using the six phono interconnects.

When the digital audio channels have been decoded, they are amplified by the hi-fi amp / processor combination in the same way as with a Dolby Pro-Logic signal, except that a 'Dolby Digital Ready' processor will have the additional output required to feed a separate active sub-woofer.



Care must be taken when selecting the additional speakers. The centre and rear speakers should have similar power ratings and performance to your existing hi-fi speakers, if possible they should be of the same type and by the same manufacturer. Matching speakers will ensure that the sound from surround soundtracks appear transparent and focused. Mismatched speakers can break down the audio soundstage and create areas of sound that spoils the surround effect.

The rear surround speakers will be affected by the type of surround sound decoding found in your system, or the type you plan to add later. For a Dolby Pro-Logic system, the audio signal to the rears has a lower power than the front speakers, and has a limited bandwidth. As a result, you can use rear speakers that are smaller and have a lower power rating because they are not likely to be driven very hard. In a digital surround sound system, such as Dolby Digital, the rear speakers are fed a signal that can be as powerful and loud as the front speakers. In these systems, the rears should be the same as the front units, or at least closely matched.



Speaker placement is important. The front left and right speakers should be placed at either side of the television, spaced apart about the same distance as the distance between your listening position and the speakers themselves.

The centre speaker should be placed above or below the television, with the front face of the speaker on the same line as the two main front units, or slightly further away. Placing the front speaker closer to the listening position will spoil front effects for people seated off-centre at the edges of the room.

The two rear speakers should be placed at the sides of the listening position, about 60cm to 100cm above head height, and pointed at each other. If this is not possible, rear speakers can be placed on the wall behind the listening position in the corners of the room, either facing across the rear wall at each other, or actually facing the wall if the speakers are close to your listening position. This last option prevents the rear speakers from sounding dominant and masking the sound from the front three speakers.

A sub-woofer can be added to most systems to carry low bass frequencies. Bass is non-directional and therefore the sub can be placed anywhere in the room - behind the sofa, in the corner, or even used as a coffee table. Move the sub-woofer around to find the position that sounds best in your room, everybody is different.