Dolby Pro Logic IIz vs Audyssey DSX vs DTS

Wall of Sound: Three new surround formats from Audyssey, Dolby and DTS aim to bring your theater sound to a whole new dimension. Literally.


You want me to buy more speakers? Yeah, I get that. To be honest, that was my first thought when I heard about height speakers. Just a gimmick, right?

Well, to find out, I journeyed up and down the California coast visiting the headquarters of the formats’ creators.

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Along the way, I learned a little something about height channels, and a little about myself.

Ha. Just kidding. But how funny would that article have been?

Why Height?

Yamaha, for ages, has had height effect channels. These aren’t exactly what we’re talking about here.

Yamaha’s height channels primarily added reverb to make your room sound like a concert hall; that kind of thing.

Generally, though, they were on to something. We humans have an incredible capacity to localize sound objects in front of us.

For most people, they can pinpoint a sound within a few degrees of accuracy. This diminishes significantly as the sound moves behind you (between 15 and 20 degrees of accuracy). Chalk this up to the hunter part of hunter/gatherer.

So adding more speakers up front makes sense: We’re more perceptive to changes there.

From a pure logistic standpoint, this is beneficial as well. It’s a lot easier to convince your spouse to run a few more wires up the front wall behind the TV than running long cables somewhere behind the sofa (if you even can).

So Audyssey, Dolby and DTS are all talking height, and in one case, width. I had the idea to go to the source and hear these formats at each company—a sort of “best case scenario.”

If I couldn’t be convinced at that level, there was no way the end product in a regular room would be able to pull it off.

Dolby’s Potrero Road building was a burlap sack factory in its former life. You can’t tell just by looking at it. Inside, though, the massive wood beams criss-crossing the facility adds an ambiance you wouldn’t expect. Or maybe you would. This is the kind of warm, quirky environment that you’d probably imagine from a tech company based in San Francisco.

The demo room was fairly small, certainly more of an office-sized testing lab than theater, but for our purposes it was perfect. The base of the setup was a fairly normal 7.1 setup with powered studio monitors.

In addition, there were three other pairs of speakers. The object of our attention was the pair mounted on the front wall close to the ceiling, about as far apart as the main left and right. To the left of the left and the right of the right were width speakers. Above and behind were rear height speakers (as I said, it’s a testing lab). We discussed how they had experimented with other positions, but having settled on height, we didn’t listen to these latter two pairs.

For most of the demo, we listened to the IIz decoding in an off-the-shelf Denon AVR-4310 receiver. The initial testing material, however, was anything but off-the-shelf.

Red Storm, developer of Ghost Recon 2, created a special prototype version of the game for Dolby with a built in software encoder of IIz. How this works is pretty interesting.

All first- (or in this case, third-) person shooters are rendered in three dimensions. In real time the hardware in the box, be it PC, PS3 or in this case Xbox 360, knows where each object is relative to the user’s avatar. This is how it creates realistic lighting, gameplay and of course, sound.

Surround sound in games is nothing new, and 5.1 is fairly commonplace. What Red Storm created for Dolby is an extra level to this sound. Built into the sound code of the game is a IIz encoder. This figures out what sounds should be above the user. In this demo, that would be an angry helicopter. I haven’t played this game, but there are a lot of angry people running around trying to shoot you. Maybe they need a hug.

The helicopter’s sound is encoded as a matrixed sound in the discrete surround channels of the standard 5.1 Dolby Digital mix sent to the receiver. The receiver sees the IIz information, strips it out and sends it to the height speakers. The effect is excellent.

As an avid FPS fan, any increase in my ability to localize an object instinctually, the better. The game is in three dimensions, and to be able to have sound in three dimensions is a fantastic bonus. Moving the view around, you could move the helicopter up and down vertically, as well as the normal 360 degrees around you as you rotated your avatar or looked up and down.

Next up were some specially prepared demos from Dr. Mark Waldrep from AIX Records. He mixed two selections specifically for IIz. These, too, were to show what is possible with content created specifically for height channels. The first of these was a classical piece called “Pines of Rome” performed by the New Jersey Symphony Orchestra. I’m not sure what surprised me more, the fact that New Jersey has a Symphony Orchestra, or that they play something other than instrumental versions of Bruce Springsteen songs.

At this point we switched to a laptop doing the IIz decoding. The only reason we did this was to be able to seamlessly switch between 5.1, 7.1 and either with height channels. I bounced between these possibilities, and the effect was quite noticeable, though perhaps not as cool as tracking a helicopter with your ears. The soundstage, with IIz enabled, was just bigger. Sound was coming from in front of you, not just from small speakers at specific angles. That’s not to say imaging was sacrificed. It was just as if the 8-inch-tall studio monitors had transformed into 6-foot-tall electrostats.

Dr. Waldrep had some fun with the second selection, “El Vuelo” from the Afro Cuban Latin Jazz Project. Here, he moved instruments all over the sound field. If you’ve ever heard a really bad surround music mix, you’ll have a general idea of what this sounded like. Sorry, the only reason drums should be coming from above is if you’ve just fallen face-first into a kick drum. This was just a tech demo, and he was clearly just playing around. It did show what was possible, and that was the idea.

We moved on to “blind upmixing.” As in, standard movies using IIz processing to figure out what should be in the height speakers.

This is the real challenge, obviously, as all current and most future content won’t have built in height info.

At the beginning of Ratatouille, the “camera” moves slowly between some trees while rain falls. The 5.1 on the disc surrounds you with rain. ProLogic IIz envelops you with rain. Rain seemingly filled the room. The effect was more natural, less “created.” And this is what IIz is really all about.

The IIz processing looks at the front three channels, but it doesn’t take any sound from these channels. That’s the key, as it’s too likely the information from these channels will be localized information. It’s doubtful you want footsteps coming from the height speakers. So IIz generally figures out what are ambient sounds, and sends that to the height speakers. This may not sound impressive, but the effect is very cool, and certainly brings you more into the movie.

I brought my own demo Blu-ray, not convinced they wouldn’t just show me material they knew worked. The Brécourt assault scene in the second episode of Band of Brothers has the main characters taking an artillery position. In many ways, this was a bad way to show off IIz. Gunshots, shouting and more are all localized sounds, and not what you’d want to find in the height speakers.

Then the artillery guns fired, and the “boom” filled the room. Not in volume alone, like a big subwoofer, but as the guns fired, the natural reverberation in the soundtrack came from all around. More than with 5.1 and 7.1 alone, but more like what you’d expect if you were 70 yards from four 105s.

Dolby claims they tuned IIz to be overly conservative, so as to be sure nothing that shouldn’t be in height channels ends up there.

Audyssey’s downtown L.A. office, where we heard DSX, is a far cry from Dolby’s annoyingly gorgeous abode. It’s more of a standard office space, but nestled in the middle is a small theater for testing. Their main lab is on the University of Southern California campus a few miles away. You know USC for their multitude of alumni in the film industry and as home of L.A.’s only professional football team.

And that, folks, is my one sports joke. Tip your waitresses.

DSX takes a slightly different approach to extra channels. They think height is all well and good (and is included in their spec), but their real push is width. Add two speakers in between your front left/right and the surrounds.

I was extremely surprised at how noticeable this effect is. Using a clip of Wall-E, the extra speakers were turned on and off. At the very least, pans from front to back were far more fluid. Sound passed seamlessly from front to back, with much less of a jump from front to back than some 5.1 systems can have.

But that’s not the real bonus. Here, like with IIz, the soundstage just exploded.

With DSX on, everything seemed bigger. The screen seemed bigger and the soundtrack seemed bigger. Everything was just more engrossing. It was closer to that Holy Grail of not being in a great home theater, but transparently being transported into the movie.

I don’t throw that around lightly. In my mind, very few systems are transparent enough to let me forget about the system and just be absorbed by the movie. But maybe that’s just me. I mean, look what I do for a living.

Regardless, making a system with small speakers sound like a system with big speakers is no small feat and one that I think is worth most people checking out.

Here too, relatively small bookshelf-sized speakers seemed significantly larger with the added processing/speakers.

One advantage of DSX over IIz is that you have the option of width or height, or both. Listening to a 9.1 system with width and height is really impressive. You get the verticalness of IIz with the extra width and smooth pans of width channels. Yes, I just wrote you get width from width channels. Hi, I’m a professional writer.

That said, all DSX is going to be created on the fly. At the moment, this is true of IIz as well, but it is more likely that Dolby, with all their contacts and clever matrixing of the signal, will get IIz on Blu-ray or more likely, in games.

Is dedicated content a huge deal? I’m not sure. Probably not, but I guess we’ll have to wait and see if real content comes out, and we can A/B encoded IIz with upmixed DSX. Regardless of how it’s created, you’re not getting localized content in these speakers, at least with movies.


At the time of this writing, all that has been shown of DTS’s height format was a demo at CES. This upmixed 11.2 demo had four height channels. DTS-HD can natively support over 2,000 individual channels, so according to DTS adding any number of discrete height channels would be easy.

Past this, DTS had no other info for me for this article. They couldn’t comment on potential licensees, or on placement of the actual channels. I’ll let you know more when I know it.
Up and Out?

There has been a lot of negative press about these new height formats, as many who were writing about them clearly didn’t understand what they were for and what they could do.

As Craig Eggers from Dolby put it, this isn’t about planes flying over your head during Top Gun. The best way to think of these speakers is as added ambient sound, expanding the sound envelopment of your audio system. It makes the soundstage of your current system larger, without having to add larger speakers. More speakers, sure, but certainly not larger.

But that’s the effect you get: larger audio.

Personally, I’d take width or height over surround back in a 7.1 system. The effect with the height or width speakers is far more pronounced and enjoyable to me than the occasional effect you’d get with surround back speakers.

That said, it’s really going to depend on your room and system. If you have a long theater and big speakers, surround back may work better for you. If you’re like most people and you have smaller speakers and an average-sized room, height or width speakers will definitely add a new element to your system. There are receivers and processors shipping now that offer DSX and IIz, so most likely your next receiver will have one or both of these formats. The Denon AVR-4310 we used in the Dolby demo, for example, has both.

I’ll leave with this: During Audyssey’s demo day, Tomlinson Holman, Chief Science Officer of Audyssey (and the TH in THX), gave us an interesting demo in their main USC demo room. It was pink noise, first running mono, then stereo, then 5.1, 7.1, on to width speakers and so on.

Obviously the biggest noticeable change was from mono to stereo, and the next closest was from stereo to 5.1. After that, you get diminishing returns. Are height or width speakers going to change your life, or be as amazing as that first time you added surround sound to your theater? No. It is definitely an incremental improvement. But in creating a more engrossing, enveloping wall of sound, it’s a fantastic effect.

Will I recommend it for everyone? No. But I’ll be honest, now that I’ve heard it, I’ll be adding it to my theater.


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