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Dolby Pro Logic IIz vs. Audyssey DSX vs. DTS

September 23, 2009 By Geoffrey Morrison

Click the images below for bigger versions:
The demo room/lab at Dolby’s Potrero Avenue building was decked out with tons of speakers and equipment. The laptop (bottom middle) allowed for instant switching between formats.
With a “basic” 7.1 height setup the surround back channels are ditched in favor of front height channels mounted high as possible on the front wall. Dolby's ultimate system is keeping the surround back channels and adding the height for a full 9.1 setup.


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.  



Wow, thanks for a GREAT, and eye opening article!
I bought Yamaha's RX V1 Flagship mainly because of Cinema DSP w/front effects channels. It is nice to see competing technology to the Yamaha. I don't want to give up my front effects speakers. I am leaning towards the Audyssey system, mainly because of the side effects channels. I have an old ADS digital time delay with side mounted speakers, and saw for myself how it can expand soundstages. Plus, and this may sound stupid, I TRUST Tomlinson Holman. I owned an old APT amp/pre amp from his old company APT. It had a real cool way to reduce separation between the two main stereo speakers w/o getting a HOLE in the middle! Tom, if you are listening, old friend, consider putting that feature BACK into your Audyssey surround circuit, save us from buying center channels , LOL

I would rather have 9.2 with 5 channels up front two at 90 at -120,-90, -60, -30, 0 (=Center), 30, 60, 90 and 120 degree angle around the room :)

Geoffrey, I love your articles as well. It's not that your on the cusp of a new technology or write it well in layman's terms. Many do that. It's your refusal to be convinced by smoke and mirrors. The no-nonsense approach. Is it good or is it marketing? And some humor thrown in. I actually read another article you wrote on Laserview from April of last year and was impressed enough to click your name to find a follow-up article. I wasn't successful, but this article is amazing. I didn't know these were in the works. I'll be coming back to read more from your articles so I don't miss out. Keep up the good work. :)

Tim Bogle

Anon, no where did he say 7.1 back channels are a waste. YOU made that up and it's misleading as it suggest the article states your opinion. It does not.

We have demo rooms with both 5.1 and 7.1. NO ONE prefers the 5.1 over 7.1 EVER. You could be the first though, LOL. So, as far as our customers are concerned, 7.1 has value.

Now, to add the lastest configs! Cant wait to test.

I completely agree that the back channels added with 7.1 are a complete waste. I am glad to see that more sensible work is now being done with DSX and PL2z. It sounds like Audyssey DSX is the best way to go giving you the option for both width and height.

Love your articles!

Jay Garbutt

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