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BEGINNERíS GUIDE TO HOME CINEMA

 

Q. WHAT IS HOME CINEMA?

Home cinema is all about recreating the experience of watching a movie at the cinema, at home, in your living room. The basic ingredients are a large-screen TV -- the bigger the better --  a surround-sound decoder connected to a multi-channel AV (audio-visual) amplifier, feeding set of speakers located around the viewing position. The decoder and amplifier can all be in one box, as part of a hi-fi system, or built inside a TV, VCR, satellite receiver, active loudspeaker, even a TV stand or console. You also need one or more source components, such as a NICAM video recorder or laserdisc player.

 

Q. WHAT IS THE IMPORTANCE OF A NICAM VCR?

In most home cinema systems a NICAM video recorder is the main source component. NICAM VCRs give you two bites of the cherry; all of them have high performance stereo hi-fi audio systems -- for movies on tape -- as well as NICAM (near-instantaneously companded audio matrix, but donít let that worry you...) decoders for digital stereo TV sound. Both NICAM and the VHS stereo hi-fi audio system are transparent to the surround-sound information contained within the soundtracks of many recent movies available on tape, or broadcast on TV. The signals pass through the VCR to the surround-sound decoder, which unravels the extra audio channels, before theyíre amplified and piped to the speakers.

 

Q. WHATíS THE DIFFERENCE BETWEEN ALL THE DOLBY FORMATS?

Dolby Stereo is the name given to the system used to encode four audio channels (right and left stereo, rear effects and centre-front dialogue), into the two-channel stereo soundtracks on many movies made since 1976. When those movies are transferred to video tape and disc, or shown on TV, the stereo soundtrack containing the multi-channel audio is called Dolby Surround; it also applies to surround soundtracks on made-for-TV series, i.e. the Simpsons, and Star Trek TNG, etc. To hear the Ďextraí channels you need a decoder. The simplest one are called simply Dolby Surround decoders, and they can extract three, (sometimes four) channels. Nowadays most decoders use the more advanced Dolby Pro-Logic (DPL) system, to accurately resolve all four channels, they use the same technology as surround-sound decoders used in cinemas. Dolby have recently developed a six-channel digital surround-sound system called AC-3, but it will be a while before thereís enough source material, and affordable hardware, for it to have an impact on the domestic market.

 

Q. WHAT EQUIPMENT DO I NEED?

If youíre about to upgrade your TV, and you want to keep things simple, it might be worth thinking about a home cinema model with a built-in Pro-Logic decoder. Virtually all DPL TVs come as a complete package, with all necessary extra speakers, just connect it up to a stereo VCR. If you want to stick with your present TV, and itís got a good-sized screen (sets with smaller screens -- less than 26-inches say -- lack visual impact), you can use your hi-fi as the basis of a surround-sound system by adding a separate Dolby Pro-Logic decoder. Alternatively you could replace the systemís stereo amplifier with a multi-channel AV amp with a built-in Dolby decoder. You can retain the hi-fiís stereo speakers, (placing them either side of the TV screen) but you will probably need to buy extra some speakers for the extra sound channels.

 

Q. WILL ANY OLD SPEAKERS DO?

If you go for a full system you will need at least three extra speakers, two for the rear effects channel, and one for the centre-front dialogue channel. Itís not necessary to spend a fortune on back speakers. The rear channel has a fairly limited bandwidth, and a lot of people get by quite happily with a pair of speakers salvaged from a retired stereo. The centre front channel doesnít carry a lot of detail either -- mostly speech -- but as the speaker has to be placed very close to the TV, it should be magnetically shielded, to prevent the magnet inside causing colour Ďstainingí on the screen. Surround-sound speakers are available singly, or in packages, some include specially-designed front-channel speakers as well.

 

Q. IS IT WORTH BUYING A LASERDISC PLAYER?

After live TV broadcasts the next best AV source, in terms of picture and sound quality, is LaserDisc. For movie enthusiasts there is no alternative, but there are a few points to bear in mind. Firstly, only a small proportion of movies released on tape end up on laserdisc as well, and only a small number of those are recorded using the PAL colour system, thatís compatible with UK TVs. Fortunately most laserdisc players these days can replay NTSC coded discs, meant for the US market, that are imported into this country. Discs are expensive, they typically sell for between £30 to £50, compared with £15 or so for a movie on tape (or £2.50 for an overnight rental...) The players arenít cheap either, a basic one will set you back around £500, but if you want the best quality, it could be a price worth paying.

 

Q. WHAT ABOUT THESE SURROUND-SOUND TVs?

NICAM stereo TVs with built-in Dolby Pro-Logic surround-sound decoders are undoubtedly the simplest way to get into home cinema. Theyíre very convenient, everything you need (apart from the VCR), comes in one box, but they can work out quite expensive. Six hundred pounds buys a modest 25-incher, but you really should be thinking in terms of 28-inches, (£700 to £1000 plus), so the picture does justice to the sound. Most DPL TVs work quite well in averagely-sized living rooms, but they tend to have fairly low-powered amplifiers, and the stereo speakers are normally built-into the set, which restricts the size of the soundstage.

 

Q. CAN I GET SURROUND SOUND FROM A TV WITHOUT EXTRA SPEAKERS?

Yes-ish... JVC have come up with something called 3D Phonic, fitted to their AV-29SX Symphonix TV. It claims to be able to produce 4-channel surround-sound effects from the setís two on-board speakers. It works by electronically re-processing the rear-channel sounds from a Dolby Pro-Logic decoder; the signals, which represent what you would hear from rear channel speakers, are fed through the front speakers. Some people say they can hear sounds coming from behind them, others are not convinced. The best thing to do is try it for yourself.  In the end, though, the only certain way to create an authentic surround sound effect is to have speakers placed in front of, and behind the listening position.

 

Q. IS THERE SURROUND SOUND STUFF ON SATELLITE AND NORMAL TV?

The information used to create the four sound channels of a Dolby Surround soundtrack are contained within two normal stereo audio channels. Surround sound information survives intact on any reasonably competent stereo system. Obviously that includes VHS stereo hi-fi, but it rides quite happily on NICAM digital stereo TV sound, (used by the BBC and ITV), and the stereo sound channels used on satellite TV broadcasts. So the answer is yes, the only trouble is there are areas in the country where NICAM is not available, moreover the BBC and to a lesser extent, the ITV companies, are notoriously bad at indicating that a movie or TV programme has a Dolby Surround soundtrack at the beginning, so you may not know to switch on the decoder, or set the TV to the correct mode.

 

Q. DO I NEED SPECIAL LEADS AND CONNECTORS?

The AV source component in a home cinema system, whether itís a stereo VCR, satellite receiver or a laserdisc player, has to have its stereo audio output connected to the line-input of whichever component contains the surround-sound decoder (AV amp, hi-fi system, TV etc.). Clearly you need the correct leads, which is usually a simple phono-to-phono cable, or a more elaborate multi-pin SCART connector. Always buy good quality branded leads from a reputable dealer. Leads with gold-plated connectors give a better electrical contact, and they wonít tarnish, so if you do a lot of switching around, live in a damp atmosphere, or are just fussy, then they can be worth paying a little extra for.

 

Q. SOME SURROUND SOUND AMPS ARE PACKED WITH GIZMOS, WHAT DO THEY DO?

Many Dolby Pro-Logic AV amplifiers have additional facilities, that manipulate the sound output in a variety of ways. Normally these do not affect Dolby Surround output, Dolby are very strict on this point. However, they can be used to liven up non-Dolby material, both stereo and mono, using a technique known as digital signal processing (DSP). Most DSP systems attempt to re-create the acoustic properties of a range of four or five different venues, from a small basement club, to a large auditorium or open air stadium. They do this by mixing in small amounts of reverberation with the original sound. This simulates acoustic reflections, as sounds bounce off walls and ceilings. The effects can be quite interesting, but the novelty can wear off quite quickly.

 

Q. WHERE SHOULD I SITE THE SPEAKERS?

There are no hard and fast rules for speaker placement. Much depends on the size and shape of the room, but most people place the main stereo speakers a foot or two either side of the TV screen. The centre-front speaker can be sited above or below the screen (remember it should be a magnetically shielded type), and the rear channel speakers behind the viewing position. Itís worth experimenting with these, and in some set-ups they work best when the speakers are at ear-level or above, mounted on the wall. In the end though, the best way is to try a variety of locations, replaying a favourite tape and comparing the results.

 

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” R. Maybury 1995 2008

 

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