Dolby EX/Dolby Pro Logic IIx

In a 7.1 AVR, Dolby EX is the same as Pro Dolby 2X Movie with 6.1 output. Also the AVR will detect the 6.1 EX flag within the DVD. Basic limiting factor of Dolby EX is that there is lack of surround channel spacialness due to the way matrix rear surround encoding is done. Thats the primary reason Dolby recommends 7.1 over 6.1, as Dolby Pro Logic 2X gives the listener a more enhanced soundfield with rear channel separation. Dolby EX was 1st done by THX and then Dolby hired Jim Fosgate to design Pro Logic 2X due to the significant sucess of the HK/Lexicon Logic 7 as they were marketing 7.1 years before the competition.

Just my $0.01..

The basic concept is easy to understand, as long as you treat 'channels' and 'speakers' as separate entities. Think of the surround field as 4 speakers that are wrapped around the listener in a 180 degree arc. Where sounds end up on this arc is determined by where they are mixed in the left and right surround channels.

Sounds that are exclusively in the left or right surround channel will image at the extreme ends of the arc (i.e., the left side or right side speaker). Sounds that mostly in the left or right surround channel will image a little inward on the arc (i.e., between each side and rear speaker). Sounds that are exactly the same in both surround channels will image in the middle of the arc (i.e., in both rear speakers).

In a 5.1-speaker set-up, the dual-mono sounds in an EX soundtrack would have phantom imaged behind you anyway, while stereo content would have imaged towards your left or right side. Using PLIIx on a 7.1 set-up gives you the same imaging, just more stable since your using actual speakers rather than relying on phantom imaging. It's the same reason some people use a centre speaker when listening to 2-channel material: the directionality doesn't change, the imaging just becomes more stable.

PLIIx processing can mimic EX decoding when needed, by sending the same signal to both rear speakers. So if an EX encoded soundtrack has certain content that is mixed to image directly behind you, PLIIx will place it there (see second paragraph). However, if the recording engineer mixed a certain surround effect to image off centre, then PLIIx can send it to either the left or right rear speaker, since it handles each one independently. EX decoding can't do that since it is limited to a mono surround-back channel that is sent to both rear speakers.

So no need for EX auto-detect flags, no need to restrict yourself to EX decoding when listening to EX soundtracks, no need for your receiver to know that it is an EX soundtrack. When the PLIIx circuit sees the exact same sound in both surround channels, it will send it to the speakers behind you, just like the EX decoder would.

Sanjay

Strange I wonder if they re-modified the original Dolby SA10 that was modified from the Dolby CP45 back in (1999) because that had the extra support that was used for “We Were Soldiers” (2002) that uses (matrix anti-phase) this wasn’t used on consumer Dolby EX AVR just centre back and that’s it, unless you use a straight forward Dolby stereo Pro-Logic decoder and use the same re-plugging plus it will have the matrix rear or "sonic whole overhead" as it was dubbed by (Dolby, Todd-AO and Soundelux)

http://www.dolby.com/assets/pdf/pres..._Soundelux.pdf

I guess if I buy cheap AVR at (Richer sounds UK) one that has Dolby pro-logic IIx I could change the existing Dolby pro-logic decoder that I use on the split-surrounds since (1998) and then re-plug it onto the surround RCA pre-outputs, simple.

Also there is what’s called half panning where a portion of the sound will be sent to centre back or within stereo mix half way over and then hard left or right.

The decoder will see that the signal has equal strength of frequency and its in-phase it moves off and away from centre, then its heard on the left rear centre then pans hard so its on the left sidewall and vice versa.

Extract from http://www.dolby.com/assets/pdf/pres..._Soundelux.pdf:

"Dubbed Sonic Whole Overhead Sound by We Were Soldiers' producers, this enhancement is the first movie theater audio system to wed a new overhead speaker system with the standard Dolby® Digital Surround EX sound system. It is an innovation of We Were Soldiers' director Randall Wallace, working with the sound experts of Todd-AO/Soundelux and Dolby Laboratories."

Because the original speaker mix soundtrack was specifically designed to reproduce overhead shellfire and helicopter sounds, perhaps we will see a 7.1 Blu-Ray of We Were Soldiers authored in the [DTS-MA named] 7.1 Center Overhead speaker layout [L,R,C,LFE,Ls,Rs,Cs,C-Oh], which adds an overhead speaker to the Standard 6.1 speaker layout, or in its Dolby TrueHD equivalent. [Note: The speaker DTS calls Center-Overhead is called Top Surround in Dolby Labs speaker layouts.]

For 2-channel sources, PLII and PLIIx use the same surround processing algorithms. Even though PLIIx came years later, it is not an improvement over PLII but instead an eXtension (more channels) to PLII technology.

To answer your question above: PLIIx Music mode is equivalent to PLII Music mode, with the only difference being number of channels (PLII is limited to 5 output channels max while PLIIx can be 6 or 7 output channels).

For discrete multi-channel sources, it is impossible to compare the two modes since PLII can only be applied to 2-channel material.

Sanjay

Yep, both PLII and PLIIx have three modes: Movie, Music and Games.

Sanjay

Sorry, but you gave the wrong infor. DD EX is not the same as DPL 11x. the difference is that in EX the rear center is mono but in IIX the rear center is stereo. Also, EX has nothing to do with THX.

Hmmm, now that may change my mind in buying the format. The diagram only uses a single overheard the original consists of many placed overhead to give uniform coverage.

With analogue processing circuits disappearing, most companies (not just Dolby) were designing their decoding and processing technologies with DSP chips in mind. For example: even though Jim Fosgate created PLII on an analogue circuit board, Dolby always intended the processing to be done in the digital domain.
Yes, always. However, there was one vacuum tube pre-pro that did all its PLII processing in the analogue domain: FAP V1. Alas, there was no such pre-pro for PLIIx.

Sanjay

In an attempt to aid (or possibly to hinder!) understanding [the differences between/common features of] DD EX and DPLIIx, Dolby conveniently provides the following:

Dolby Pro Logic IIx FAQ

Dolby Digital EX

Dolby Digital Surround EX This material is not completely unambiguous, and it does not even begin to address the variations in implementation [and poor labeling/description] which may exist in a particular manufacturer's product line...

Can't find anything on PLIIx, but here's a pretty good description of PLII:

http://www.dolby.com/assets/pdf/tech..._Operation.pdf

Just remember that the DTS-MA 7.1 Center Overhead speaker layout [L,R,C,LFE,Ls,Rs,Cs,C-Oh] is really an authoring OR playback CHANNEL mix for use with, e.g., Blu-Ray, which is why there are only 7.1 speakers (i.e., CHANNELS) shown in the schematic. However, nothing therein prevents your replacing the single overhead speaker with a multi speaker array for PLAYBACK, with/without post-processing [perhaps some kind of 3D DPLIIx and/or THX-style decorrelation(?)] [and with the problems/issues associated with multi speaker vs. single speaker reproduction!] to deliver the Center-Overhead channel. [Edit: I'm not sure I'd want one speaker over my head, never mind an entire array!]

A more significant issue is that I know of NO current home theater processor which has a DTS-MA/TrueHD speaker [playback] layout which includes any of the new vertical speakers. And I would expect that a lossless remap from 7.1 Center Overhead to 7.1 Standard would effectively eliminate the focus of the overhead soundstage.

As to the near(?) future: I can't see any reason why the [amplifier] channel which is left unused when a 7.1 channel receiver is configured in 6.1 Standard [L,R,C,LFE,Ls,Rs,Cs] mode could not be used to allow the receiver to function either in 7.1 Center Overhead mode or 7.1 Center Height [L,R,C,LFE,Ls,Rs,Cs,Ch] mode [intended to emulate the IMAX speaker configuration?]; that should be little more than a firmware change... [Edit: No, I'm not suggesting that existing receivers could be upgraded; rather I'm saying that the incorporation of 7.1 Center Overhead mode and/or 7.1 Center Height mode as speaker layout options should add negligible complexity/cost to future 7.1 channel receiver/processor models.]

Read closely..
EX is the same PL2X Movie but in 6.1, which means that when the DSP finds the EX flag both back L/R surround channels have the same mono info. However if the incoming source stream is 5.1 (such as Dolby Digital) and being postprocessed by DPL2x to 7.1, the back L/R surround channels output will be in stereo which provides enhanced channel separation.

Hope that clears up any confusion.

Just my $0.01..