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Will Dolby Pro Logic IIx hurt the fidelity of true 5.1 surround sound?


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#1 of 8 soccastar001

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Posted March 28 2012 - 06:00 AM

I have a receiver with Pro Logic IIx decoders (one for movies, music, and games). I know that these decoders are used to produce surround sound from stereo audio. My question is if I play a video with a true 5.1 surround sound track is this decoder going to try to take action on that track as well and hurt the fidelity of the surround sound or will it recognize that it is already a 5.1 surround sound track and let it play in its source form?

#2 of 8 Steve Tannehill

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Posted March 28 2012 - 06:14 AM

Hi, Tony, welcome to HTF! I would guess that your receiver would have a "direct" mode that allows 5.1 sound without any DPLIIx processing added to it. What receiver do you have? Does the manual say anything?

#3 of 8 soccastar001

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Posted March 28 2012 - 06:41 AM

It does. The reason I'm asking is I'm wondering if I put it in Pro Logic IIx mode will I be able to play both stereo sound through my 5.1 setup as well as DD5.1 steams without them being altered by the Pro Logic IIx codec? The manual of my receiver doesn't make any mention of it. I have a Yamaha RX-V495

#4 of 8 Steve Tannehill

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Posted March 28 2012 - 07:00 AM

According to this: http://www.dolby.com...-logic-iix.html Dolby Pro Logic IIx alters 5.1 sound to play back in 6.1 or 7.1. So depending on your speaker configuration, you are getting extra processing on top of the 5.1 stream.

#5 of 8 KPmusmag

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Posted March 28 2012 - 07:46 AM

I have a 7.1 system with quite a variety of flavors when it comes to surround processing. I find it absolutely depends on the source, and I experiment with it quite a bit. For example, I have found that I prefer the "direct" option (no processing) when watching the blu-ray of THE SOUND OF MUSIC, while for CASINO ROYALE (2006), which has a 5.1 soundtrack, I prefer the Pro Logic IIx setting because it fills in the other two channels and it just sounds richer to me. I suppose the "direct" option is the one to use to hear exactly what is on the disc, but for some movies I like what the processing does. Purists will be horrified at this, but when I watch CASABLANCA I have it set for quite a distant echo in the rear channels because when I first saw CASABLANCA in a real film theater, it was The Granada in Santa Barabara, which has (had?) a huge auditorium with a big natural echo and I love to relive that. Push buttons until it sounds pleasing to your ear because everyone will have a different opinion. Back when home video was first starting to include stereo soundtracks (linear VHS stereo - remember that? - and how about laserdiscs before CS noise reduction and digital), I had such fun building a hafler circuit with about $3.00 worth of parts from Radio Shack and experimenting to find out what I could get from different videos. My Dad didn't believe it would work, but I had him sit down for the scene in STAR WARS where Luke grabs Leia and does the Errol Flynn bit, and when Luke's voice echoed from the back speakers, Dad was impressed!

#6 of 8 soccastar001

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Posted March 28 2012 - 07:49 AM

What will it do when I only have a 5.1 setup? Or maybe a more helpful question to ask would be how do I configure my receiver so that I can play DD5.1 steams on my 5.1 setup in their pure form but also play stereo streams on my 5.1 setup out all speakers instead of just the front 2?

#7 of 8 KPmusmag

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Posted March 28 2012 - 08:24 AM

I am not an expert, so hopefully someone else will chime in - but if your receiver works like my Onkyo, there is no one setting that will do both. You would want to set it for "direct" (or whatever word your receiver uses to describe no processing) for 5.1 sources but then change it to Pro Logic IIx for 2.0 sources so that the receiver decodes the matrixed info and expands it out to 5.1.

#8 of 8 John Garcia

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Posted March 28 2012 - 09:01 AM

What will it do when I only have a 5.1 setup?

Nothing.

Or maybe a more helpful question to ask would be how do I configure my receiver so that I can play DD5.1 steams on my 5.1 setup in their pure form but also play stereo streams on my 5.1 setup out all speakers instead of just the front 2?

Again, you don't need to do anything. Simply selecting PLIIx will distribute it to all channels.

I am not an expert, so hopefully someone else will chime in - but if your receiver works like my Onkyo, there is no one setting that will do both. You would want to set it for "direct" (or whatever word your receiver uses to describe no processing) for 5.1 sources but then change it to Pro Logic IIx for 2.0 sources so that the receiver decodes the matrixed info and expands it out to 5.1.

Yes, this is the answer except that "direct" usually means bypassing all processing/bass management. Generally the term is "auto" allowing the receiver to automatically choose the best (or previously used) method for a given source type.
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