How To

In the last "Shop Talk" I touched on the various factors that affect your home theater choices and plans. This time I go into more detail about the single feature that puts the theater in home theater: the video display. Without this little item, all you've got is multichannel sound!

Obviously, we all want a large TV, but size is only one issue—and picture size is only (excuse me, but I have to say it) part of the picture. Here are the basics you'll need to make sense of the options.

Define Definition
Conventional TVs (sometimes called standard-definition television, or SDTV) operate on a broadcast protocol called NTSC, named after the National Television Systems Committee, which drafted it. But we're seriously into high-resolution video here at Stereophile Ultimate AV, so our natural inclination is to tell you to buy a high-definition television—or, at the very least, an HD-ready TV (more on this later).

NTSC was codified before movies went widescreen. That was just one of the issues that HDTV set out to solve. Where SDTV has an aspect ratio of 4:3, HDTV has an aspect ratio of 16:9—33% wider, and perfect for showing widescreen movies. You can buy HDTV-ready TVs with either 4:3 or 16:9 ratio screens, but widescreen models now dominate the market.

Other issues addressed by the HDTV format include picture quality (resolution), sound quality (and quantity—HDTV has 5.1-channel sound), and better reception. And HDTV also does away with NTSC's Rube Goldberg interlaced-scan process. Or one form of HDTV does, at least. HDTV provides broadcasters the option to use progressive scan technology: instead of refreshing only every other line of each frame first, then the other, this system scans or displays each frame all at once.

The Resolution Will Be Televised
HDTV can handle progressive scanning, but its protocol (called ATSC, after the Advanced Television Systems Committee, which developed it) doesn't insist on it. HDTV can be either 720 lines, progressively scanned (720p), or 1080 interlaced lines (1080i). Most HDTVs today will accept both of these formats (plus standard-definition 480i or 480p) and convert them as required to the set's native resolution.

The important thing to understand about HDTV resolution is that you're getting more information on your screen at all times. In our digital TV age, resolution is specified in pixels, or picture elements. (Resolution was specified in lines when all displays were CRTs; and we still use lines of resolution for some applications.) NTSC TVs give you a little more than 200,000 pixels per image (the exact resolution will depend on the source); HDTVs up that total by a factor of ten: 1920 horizontal pixels times 1080 vertical pixels equals more than 2,000,000 pixels per image. More pixels is better—a lot better.

What Was That Middle One Again?
To be advertised as an HDTV television, a set must include a built-in HDTV tuner capable of receiving high-definition transmissions over the air. Another choice of TVs teeters precisely between the old-school NTSC-only-capable TVs and the HDTV products that represent the future of broadcasting: I'm speaking of HDTV-ready televisions. These babies have the higher-resolution displays of HDTVs, but need to be connected to a separate HDTV tuner to receive HDTV's digital broadcasts. Fortunately, most HDTV-ready TVs have an NTSC tuner so you can watch your regular over-the-air (OTA) and cable TV shows.

But why buy only an HDTV-ready television? Price, for one thing—HDTV-ready sets tend to be quite a bit less expensive. Furthermore, some areas have greater access to OTA HDTV transmissions than others (many rural counties have no OTA access at all), and even satellite services offer only a limited amount of programming.

You Can Never Be Too Wide or Too Thin
Once you've decided whether you're going to stick with SDTV, opt for HDTV, or split the difference with an HDTV-ready set, you still have a staggering number of options to choose from. But it all comes down to a simple question: What kind of video display do you want?

The cathode-ray tube (CRT) television was the only choice for TV's first five decades or so, but CRTs don't get much attention these days. Going solely on picture quality, the direct-view CRT might still be king. But CRTs are inherently analog devices, often require frequent adjustment, and tend to be heavy and bulky (read: deep).

For big TVs, flat is where it's at—at least for many viewers.

Plasma displays are the sexy technology that's getting most of the buzz right now. They are thin—from 3 to 5 inches thick—and they're available in screen sizes up to just over 60 inches, with larger designs promised later this year. Plasma panels are bright enough that you can view them in well-lit rooms, and they look good even at viewing angles that aren't right smack dab in the middle of the sweet spot.

So far, however, plasma displays haven't been particularly good at reproducing the true black levels required by a detailed video image, they're prone to burn-in if you leave a stationary image frozen on the screen for prolonged periods, and they're expensive.

There are other flat-panel technologies. Liquid-crystal displays (LCDs) are ubiquitous at the smaller screen sizes, but at the most recent Consumer Electronics Show (CES) in Las Vegas, an increasing number of large-screen LCDs were on display, many of them extremely impressive. LCD flat-panel displays have been around for nearly 20 years—you probably own one if you have a laptop computer. Liquid-crystal displays don't do pure black well, either. And, as can be attested by anyone who's tried to read over the shoulder of a road warrior working during an airline flight, their pictures aren't really viewable from off to the side of the display.

Shrinking the Big Boxes
When you hear the word projection, you probably conjure up images of those expensive front-projection systems that guys like UAV editor Tom Norton get to play with. Well, we'll be getting to those—but one of the biggest areas of growth currently is in rear-projection televisions (RPTVs).

In the old days, RPTVs were based on cathode-ray tubes, which beamed their light onto a mirror, which then projected it onto a translucent screen. Early RPTVs were humongous, and their pictures were dim and less than sharp—some wags dubbed them "Blur-o-Visions."

Contemporary RPTVs are sleeker, sharper, and brighter. One common type uses LCD technology, but an increasing number of designs use digital light processing (DLP). Described by PC Magazine as "the weirdest technology ever invented," DLP is based on an optical semiconductor chip known as the digital micromirror device (DMD). What's so weird about a DMD is that it's a single chip containing a rectangular array of up to 1.3 million hinge-mounted microscopic mirrors, each less than one-fifth the width of a human hair. When stimulated by a digital video signal and combined with a light source, a color wheel, and a projection lens, the DMD's mirrors reflect an all-digital image onto a screen or the front panel of an RPTV. It's almost miraculous that it works at all—but even more amazing is how well it works. Best of all, it's relatively affordable.

That's not to say that DLPs are perfect. That "color wheel" I slipped into the paragraph above replaces the three-color pixel groups found in plasma and LCD displays (or the three separate color guns in a CRT). A color wheel is a spinning disc located between the lamp and the DMD that filters the light into red, green, and blue. In single-chip DLP projectors, this can produce what's often called the "rainbow effect": a multicolored shimmer that's visible—usually in peripheral vision—when a viewer changes his or her focus from one part of the screen to another. Manufacturers have discovered that three-chip DLP projectors, faster color-wheel speeds, and more sophisticated color-wheel designs can minimize or even prevent the effect.

An even newer technology that shows great promise for RPTVs is liquid crystal on silicon (LCoS). Unlike conventional LCDs, which are transmissive, LCoS is reflective. A complete explanation of this distinction is a story for another time, but basically, an LCoS design can move the pixels closer together, making the pixel structure even less obvious and the picture much sharper. LCoS also promises better color uniformity, sharpness, and brightness.

Sitting in a Dark Room Looking at Moving Pictures
If you want to re-create the movie-theater experience precisely, you'll want a front-projection system. These eliminate most space problems by getting rid of the box entirely. Well, almost—you still have to put the projector somewhere. Some of them, such as the state-of-the-art, three-bulb, 9-inch-CRT projectors, can be quite large—not to mention expensive.

But if you want movie-theater picture quality at home, a CRT projection system is still the way to go. In addition to being large and costly, these systems are also somewhat intimidating and are best installed by experienced professionals, preferably those trained by the Imaging Science Foundation (ISF). Fortunately for those of us with budget constraints, there are other front-projection options.

Stylishly compact, featherweight home-theater projectors are available that employ DLP, LCD, and even LCoS technology. For many viewers, a projector can be the answer to their HT prayers, but light control remains a major sticking point—projectors work best in rooms that are dim, if not completely darkened. They also require screens—and specialty screens exist that assist each type of projector to offer the brightest, sharpest picture possible.

You Pays Your Money and You Takes Your Choice
Obviously, there is an abundance of choice when it comes to choosing a new television, and choice is good. With all the possibilities currently available, there's bound to be one that's right for your room and your budget. Winnowing the field down to just one option might take a bit of research—but exploring the wide world of high-performance video devices is the kind of chore most of us thrive on.

Now you're armed with the basics. In a future installment we'll go into more detail on what you should watch for—and watch out for—when hitting the shops for a television.

Enjoy the hunt!