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It was inevitable. As soon as we’d got used to the idea of Dolby Pro-Logic four-channel surround-sound -- maybe even brought some gear -- along comes an even more sophisticated system, with bigger and better bells and whistles. Not surprisingly it comes to us courtesy of Dolby Labs, and you’ll be even less amazed to learn that it’s a digital system. We’ll come to know it and love it as Dolby Digital but most people within the home entertainment industry still prefer to call it AC-3, you may even hear it referred to by some old-timers as Dolby 5.1.


AC-3 as we’ll call it from now on -- to save ink -- is a development of the six-channel SR-D surround-sound system, widely used in cinemas. This domestic variant has five discrete, full-bandwidth channels (3Hz to 20kHz), that are used to drive speakers for right and left stereo, a centre dialogue channel, plus rear right and left channel surround channels. The sixth, narrow bandwidth channel drives a sub-woofer, carrying low-frequency sounds and effects. In other words surround sound effects are bigger, more dynamic and a lot more exciting; it makes Dolby Pro Logic sound like cheap stereo!


Currently AC-3 encoded recordings are mostly confined to imported NTSC Laserdiscs, where the signal replaces one of the two near-redundant analogue FM soundtracks, (the normal 16-bit stereo soundtracks are unaffected). Unfortunately it can’t be used on PAL Laserdiscs, because the 625-line picture signal takes up more room, but we’re likely to be seeing and hearing a lot more about AC-3 with the imminent arrival of DVD.


It now seems highly probable that many mid-range and top-end European (Territory 2) PAL DVD players will have dual-standard AC-3 and MPEG 2 ‘Musicam’ sound systems. That means they will be able replay imported ‘general release’ Territory 1 (USA) discs, that have AC-3 soundtracks. However, new releases will almost certainly have territorial coding, to prevent then being played on machines in other countries, ahead of their scheduled release dates. At the time of writing it was still unclear whether discs would have one or both types of soundtracks, ‘a decision is expected very early in 1997’ according to one source close to the discussions.


Forward thinking manufacturers including Linn, Kenwood, Marantz, Meridian, Sony and Yamaha have already launched AC-3 processors and compliant AV amplifiers in the UK, that can be teamed up with AC-3 compatible laserdisc players from Denon and Pioneer (or upgraded versions of existing models).


If you thought Dolby Pro Logic was good just cast your ears over AC-3, and listen to the future!



We’ve become accustomed to seeing science fiction technology turned into reality but the flat, hang-on-the-wall video or TV display has stubbornly defied the best efforts of the world’s consumer electronics industry. It’s been a favourite prop in futuristic movies and comics since the 1930’s but one of the earliest sightings goes back to an article in the magazine Popular Wireless*, published in 1922, predating Bairds first successful TV experiments by several years. The illustration shows a family sitting in front of a large flat wall-mounted display screen, with the man of the house in charge of the remote control -- they got that bit right at least... Needless to say more than 70 years later we’re still waiting, but maybe not for much longer!


Small flat screen video displays have been around for at least the past twenty years, on personal TVs, camcorders and laptop computers, but the problem has always been to scale them up, to the proportions of a decent-sized living-room TV, at a price consumers would be prepared to pay.


The main difficulty is consistency. Most types of flat screen displays depend on hundreds of thousands of individual picture elements or pixels, and they’ve all got to work. One faulty pixel, especially if it’s close to the middle of the screen, is enough to render it useless. The larger the screen, the harder they are to make, and the higher the reject rate. In the past ten years improved manufacturing techniques have resulted in a steady increases in size and reliability, with consequent reductions in price, but the largest commercial LCD screens still don’t go much above 15-inches, and they still cost up to ten times as much as a similarly sized CRT-based TV.


Flat-screens took an interesting turn almost four years ago, when Matsushita announced the development of the flat Plasma screen. Plasma screen is a hybrid technology; light from a phosphor-coated screen -- similar to a CRT -- is triggered by UV discharge from a gas plasma inside a glass envelope, controlled by a display matrix. This technique overcomes many of the disadvantages of LCD screens: Plasma displays are easier and cheaper to manufacture, they have a wider viewing angle, and they’re much brighter, in fact performance compares well with traditional picture tubes. The concept has been steadily refined, and many of the world’s leading set-makers have jumped aboard the flat-screen bandwagon.


Ironically it’s unlikely many of the plasma screen TVs promised for the next couple of years will be easily wall-mountable. The envelope is made of thick glass, which makes them all quite heavy. A modestly sized 26-inch 16:9 plasma screen weighs up to 20kg, associated power supplies AV circuitry and speakers add another 5-10 kg (Panasonic and Sony put their tuner and power supplies in a separate box), all of which will require a pretty substantial wall to hang it on, and some means of hiding a lot of ugly dangling cables!


(*NB -- I have a copy, if you need an  illustration)



Ó R. Maybury 1996 1012




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