THX began life as part of LucasFilm. The brainchild of Tomlinson Holman, the initial goals for THX was to ensure that movie audiences in theaters heard the same audio that sound engineers heard in the listening booth after the final audio mix. Eventually, that goal mutated, the idea being to ensure that home theater buffs heard the same quality and levels of audio as those sound engineers.

I’ve known about THX and audio for a number of years, even attending level 1 and level 2 training they give to custom installers. That’s where I learned the importance of room acoustics, and how your listening space often affects your listening experience far more than any set of speakers or electronic gear could.

So when I learned about THX getting into the business of certifying HDTVs, I was interested. But before we dive into what goes into a THX certified panel, let’s talk about what THX does and doesn’t do.

What is THX (and What It’s Not)

Once part of LucasFilm, THX exists now an independent, privately held company. The company’s business is split into multiple segments, including training programs, hardware certification and theater design.

There’s some confusion about what THX standards actually mean. Unlike Dolby or DTS, THX tends to stay out of the business of actually altering the signal, though they have dabbled in psychoacoustic effects, such as THX Loudness Plus, which tweaks frequency response to maintain the perception of listening to the movie soundtrack in the sound booth at reference level.

However, THX doesn’t compete with Dolby or DTS in developing primary encoding standards. The training program for audio, for example, gives home theater installers knowledge and tools to design rooms that maximize the listening experience. You learn about acoustic treatments, speaker placement, audio calibration and room design.

Most people only ever see the THX logo on hardware, and think that’s where it ends. From my perspective, the training programs are much more interesting. The audio sessions I attended went into rigorous detail on room calibration, minimizing standing waves, acoustic treatments and more. While incredibly valuable for me, these sessions also highlighted to me the essential conflict about what THX is and isn’t – more on that shortly.

Isn’t THX About Logos on Audio Gear?

Most people, however, know about THX through logos on certified hardware. When you see an A/V receiver, home theater speakers or even PC speakers, there are certain characteristics they all have in common.

On the technology front, THX acts as a consultant in the audio space. For example, the slot-driven speakers used in the THX certified Razer Mako speakers was actually designed by THX. Interestingly, that slot design by Laurie Fincham, was actually designed for automotive speakers. As more cars actually ship with true multichannel audio setups, the slot design is able to deliver adequate sound volumes from the relatively flat areas on the center of the dashboard.

The core idea, remember, is to attempt to recreate the soundscape as the mixing engineer hears it in the sound stage through reference speakers. However, different sets of hardware may reach this goal in different environments. A set of THX certified PC speakers try to recreate that soundscape in the near field environment of a typical PC user – only a couple of feet from the speakers. If you take those THX certified PC speakers and attach them to even a modest home theater installation in a small room, you won’t get that same audio experience.

When THX certifies a piece of hardware – say, an A/V receiver – it works closely with the company building the receiver. Test criteria differ, depending on certification level. The power you need for a THX Ultra 2 certified receiver, which is supposed to fill a fairly large space at reference level is necessarily higher than that needed for a THX Select 2 receiver which is designed for a more modest living room.

At the end of the day, a company pays THX for testing, certification and the use of the logo. Companies which send their hardware through the process may end up not paying for the logo, but still end up with hardware that may be better than at the beginning of the process.

Since the logo program is a major part of THX’s revenue stream, obvious potential conflicts can occur. A company building an A/V receiver can go through all the steps of certification, but there’s no guarantee that actual retail products meet the certification. To its credit, THX does have a random test program, where they go out to retailers and buy sample gear, bring it back to the lab and test it for compliance.

Confusion Begets Controversy

THX tries to define a listening (or, in the case of HDTVs, viewing) experience, rather than just a set of hardware specs. The very act of doing that makes the company somewhat controversial. On one side are the purists, who suggest that only high end products should be worthy of certification. Anything else – a THX logo on PC speakers, for example, is a sellout.

This is exacerbated by confusion between what THX tries to deliver and what any individual product might include in its feature set. Take A/V receivers: companies will bundle in extra features into THX Ultra2 certified receivers that actually have nothing to do with what the THX certification is meant to deliver. So users may assume those features are available on all products with that certification.

Then there’s confusion between audio and video certification. A good example of this was the recent controversy revolving round the Lexicon BD-30 high end Blu-ray player – which turns out to be a repurposed (and supposedly tweaked) Oppo BDP-83.

THX worked with both Oppo and Lexicon to ensure that the video capabilities met THX standards for video, including linearity of the signal and other factors. Oppo took some of what it learned, and worked that back into the original Oppo product. The Lexicon player was criticized not for just being an Oppo in Lexicon skin, but for not meeting THX audio standards… except that the player wasn’t certified for audio at all, just video.

But the very act of working with Lexicon to certify a product that was simply a repackaged and tweaked Oppo player left some analysts wondering what value THX really brings to the table. If, after that effort, all you need to do is upgrade to the latest Oppo firmware to get those video tweaks, what’s the value of the Lexicon player, other than a fancier external package and a logo? THX trades on its expertise in audio and video, but in the era of the Internet, being a company of high priests with secret sauce is a little more difficult.

All About Linearity

What does it mean when THX certifies an HDTV? There are already standards, like ATSC, for defining the HDTV signal. How the LCD, plasma or other HDTV tech interprets and plays back that signal is where THX comes in.

There are a key set of parameters that any good HDTV needs to hit in order to achieve maximum visual fidelity. Those parameters, however, don’t exist in a vacuum. Take the idea that an ideal panel will offer a gray scale color temperature of D6500. It’s easy to say that – but then you have to also add: D6500 throughout the brightness range. To achieve that linearity at D6500, THX mode dials down maximum brightness. So the tradeoff is a less bright image, which implies better light control in the room, versus a brighter image with a less linear signal.

Then there are more subjective areas, like contrast. Ideally, you do want as much contrast as possible. But having a 10,000:1 contrast ratio doesn’t mean you get great image quality, if the low range is still visibly gray and the high range is ridiculously bright.

When THX works with a panel provider, they specify settings that try to behave linearly – or at least, predictably – throughout the entire range required. You want a high contrast level, but not at the expense of a deep black level. But if hitting the deepest possible black level adversely affects pixel response time, then the HDTV may have to sacrifice a tiny bit of black level so the response time is fast enough.

Then you run into quirky behavior driven by the HDTV company’s need to compete on specsmanship. High refresh rates are a good example of this. You see quite a few HDTVs out today that advertise a “240Hz” or even “480Hz” response time. Those high refresh rates aren’t real – they’re interpolated. HDMI 1.3a and earlier don’t have the bandwidth to push very high refresh rates. Instead, the panel interpolates intermediate video frames to attain a high frame rate. This, in turn, can create artifacts or simply look odd, particularly with content originally shot on film at 24fps.

So when you enable THX mode in an HDTV, one thing that gets disabled is high frame rates, the idea being that film looks like it should.

In the Lab

All this talk about setting standards and assisting companies develop products that meet those stringent standards is well and good, but what’s involved in the testing process?

THX has both audio and video labs at their San Rafael, California facility. The audio labs include an anechoic chamber, studio space and test equipment. The HDTV test lab consists of two separate labs. One large space can be completely darkened, and is used to test panel uniformity, color tracking, color temperature and other parameters. The main instrument is a Konica-Minolta CS-2000 spectroradiometer, used to measure contrast ratios, color temperature and related specs. Also on tap is a high end digital camera back used to measure panel uniformity.

A panel manufacturer begins with very early samples, often lacking amenities like bezels, in order to start dialing in the electronics. At the beginning, the result may be pretty poor.

Image: color tracking -- bad

Over time, the panel electronics are tweaked, software updates written and all the various pieces are tuned to bring the final result close to that magical linearity.

The second lab is the subjective test lab. Tests that require visual inspection, like anti-aliasing performance, happen in this lab. While some actual content from film and video sources is viewed as a sort of final sanity check, most of what occurs is visual inspection of test patterns. Some of the testing is more aggressive than publicly available tests. For example, it’s possible that an HDTV panel might pass the publicly available HQV benchmark for anti-aliasing, but fail on the THX test.

The bottom line: there’s a ton of testing and tweaking that goes on before an HDTV receives THX video certification. How does this play in the real world? Let’s take a look at a case study.

Case Study: The LG 55LH90 LCD HDTV

LG makes a number of THX certified HDTV. The current high end of their LCD line is the LG 55LH90. This is a zone-backlit LCD using LED backlighting. In addition to THX certification, the unit offers two “ISF” settings. (ISF is the Imaging Science Foundation, which trains and certifies custom installers for home theater video calibration work.)

LG loaned me a 55LH90 to try out in my living space, so what I’ll be discussing isn’t some unit in an ideal lab, but one in my viewing room. My family room has a large glass patio door on one side, and overhead lighting which isn’t dimmable. It’s a 15’ x 15’ area, with the main seating about 7 feet back from the HDTV.

The LG unit offers a THX setting, which is set to about 130 cd/m², with zone backlighting enabled. It’s worth discussing the differences between the THX settings and the ISF menu entries.

The THX setting is tuned for film material, though certainly works well on standard HDTV content as well. It’s a “what you see is what you get” setting. In fact, many of the normally tweakable settings are grayed out. You can think of the THX setting as a sort of pre-calibrated setting suitable for relatively light controlled viewing environments.

Note how much the backlighting is dialed down – it’s set to 30%. The THX setting also disables high refresh rate and dynamic contrast ratio settings.

The ISF settings, on the other hand, are there specifically for tweaking by professional calibrators, though users are certainly free to change them as well; these are not hidden under some special factory code.

Interestingly, the 55LH90 also has a simple, but useful, calibration routine built into the menu system. If you don’t like any of the out-of-the-box settings, but don’t want to pay for custom calibration, then you can use the built in tools to perform a good, first level calibration. As with similar tools on the PC, you’re walked through a series of screens which allow you to tweak black levels, brightness and color best suited to your viewing tastes and environment.

The THX mode looks stunning to my eyes -- particularly with movie and episodic TV content. Blu-ray movies, in particular, offer up impressive black levels and terrific detail. I’ve seen a lot of LCD TVs, and have always leaned towards plasmas. No LCD TV has ever really satisfied my viewing tastes – until now. I can safely say that this LG unit is the best LCT HDTV I’ve seen to date. Even viewing angles seem better than past LCDs I’ve viewed – but bear in mind my 15x15 space means no one really sits at steeper off-axis angles.

Since most of our HDTV viewing is in the evening, light control really isn’t an issue. Even during sunny daylight, though, the brightness seems adequate in THX mode. While we do have a large sliding glass door, we never get direct sunlight into the room.

I’ve tweaked settings for other types of material. I’ve been watching the Winter Olympics in high def recently. While THX mode is sufficient, it’s not really enough, and tweaking the settings – including enabling the higher frame rate – makes viewing that type of content more enjoyable. Interestingly, the “Sports” preset was too bright for Olympics, though it did look fine when watching the Super Bowl.

Given my experience, the LG unit gets a definite thumbs up. But my experience with THX mode isn’t mirrored by others. CNET’s test lab found THX mode to be quite blue . That wasn’t reflected in the THX mode I saw, which had no visible blue cast, as an 8200K average color temperature would indicate. That points to potential product quality inconsistencies or perhaps a firmware update on my version.

There is, of course, a price premium, though not as much as you’d suspect. Recent price checks show the LG 55LH90 priced at a around $2,000. That’s not out of line for 55-inch premium HDTVs. Some Samsung and Sony units can cost quite a bit more. So for your $2K, get an excellent LCD HDTV with zone LED backlighting (not edge backlit) and a THX preset that serves quite well for movie watching. On top of that, you can tweak almost every setting to your heart’s content.

Hardware Certification: No Panacea

In the end, you have to evaluate whether or not THX meets its stated goal of recreating the aural environment of the sound mixing room or, in the case of video, what the cinematographer intended with the film. And here’s where confusion really sets in.

The implication of buying THX certified gear is that you get that sound mixing room environment. Any home theater enthusiast will know this simply isn’t the case. All the logo implies is that the amplifier will deliver a certain signal quality. Without tuning and calibration, a THX certified receiver will sound no better than any other high quality receiver that’s not certified. And if you calibrate your speakers and amplifier to your space, does THX necessarily sound better?

Let’s go back to my own environment as an example. I’ve got a THX Ultra2 certified Onkyo TX-NR1007 A/V receiver. My speaker setup consists of a 7.1 system built around Paradigm speakers: Studio 20s (left and right), CC470 center channel, CC390 left and right surrounds and AMS-150R in-ceiling speakers for the rear surrounds. The subwoofer is a Hsu Research VTF-2. None of my speakers are THX certified. For one thing, the fronts are full range, going down to about 50Hz – below the THX recommended 80Hz crossover.

I used the Onkyo’s built-in calibration system, which automagically set up the speakers as full range (large) speakers, not as THX speakers (small, with an 80Hz crossover to the subwoofer). After the initial auto-calibration, I take a sound pressure level meter and tweak the settings a bit, so that overall volume levels are consistent throughout the room. This is particularly important to minimize bass standing waves. (Although my room is square – the worst case for creating standing bass waves, a set of stairs going up into a hallway in the rear mitigates the square shape considerably.)

Even after calibration, the speakers sound best in my environment set up as “large.” I did try setting them up to the THX spec of 80Hz crossover to the subwoofer, but the result just didn’t sound as good to my ears.

Final Thoughts

In the end, THX certification brings to the table hardware that meets a consistent, minimum set of standards built around the concept of what the mixing engineer hears in the sound booth or what the director intends visually in a film. But as we’ve seen, implementations can vary and the listening or viewing space has a tremendous impact on what you hear and see.

The implications of a THX logo are perhaps stronger than the actual end result, however. The company began life to improve the aural experience of viewing film in the home. But people listen to music in stereo, watch reality TV and are sports fans. If you’re a film buff with a large budget able to build a custom home theater, paying for THX gear and paying for professional calibration is likely worth it. For the rest of us, THX certification is like Starbuck’s coffee: it’s consistent and predictable, but not always the perfect cappuccino in every situation.