Dobly TrueHD and an old receiver - AVS Forum
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post #1 of 10 Old 12-01-2012, 08:19 AM - Thread Starter
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I have an old receiver with 7.1 surround sounds. Right now I just have the three front channels plugged up and was wondering should I even plug up the two center surrounds with the surrounds speakers? I know my A/V receiver doesn't decode Dolby True HD but I guess it downgrades it to EX. Will this give me a 7.1 system setup or would it just be a 5.1? Truthfully I just want to know if it worth it to hook all 7 speakers?
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post #2 of 10 Old 12-01-2012, 09:11 AM
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I would suggest that you set up the 5 speakers and get them working right acoustically (correct placement etc.).

I doubt if your listening would be further enhanced by two more speakers.
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post #3 of 10 Old 12-01-2012, 10:01 AM
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Quote:
Originally Posted by KennyPa View Post

Truthfully I just want to know if it worth it to hook all 7 speakers?
Depends on a couple of factors, like your hearing and the seating location in the room. If you can hear the difference between sounds coming from your sides vs sounds coming from behind you, then you'll appreciate what a 7.1-speaker set-up can do compared to a 5.1 layout. However, in order to do a 7.1 set-up effectively, your seating needs to be at least a few feet away from the back wall, so you have some space behind you for the rear speakers AND they are well separated from the side speakers.

One pair of surround speakers can't be in two locations simultaneously (at your sides AND behind you), so it helps to have a 7.1 layout in order to hear stable rear-vs-side directionality in the surround field. Also, 4 speakers can literally 'surround' you better than 2 speakers ever could, so a 7.1 set-up gives better envelopment compared to a 5.1 set-up.

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post #4 of 10 Old 12-01-2012, 10:08 AM - Thread Starter
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True but do I gain anything by having a 7.1 setup. If my receiver can't decode bluray audio tracks correctly. Is Dolby Ex a 7.1 format?
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post #5 of 10 Old 12-01-2012, 10:28 AM
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Does your AVR have HDMI input?

Amir
Founder, Madrona Digital
"Insist on Quality Engineering"

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post #6 of 10 Old 12-01-2012, 10:36 AM
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Amir asks the critical question. AFAIK, SPDIF optical or coax digital connections cannot transfer 7.1 channels. Maxes out at 5.1 so you won't be able to transfer above 5.1 via spdif. HDMI can transfer 7.1, so if you have that you are golden.

Just to keep thinking straight, a receiver that had the capacity to read DTS HD or DD True HD (ie the lossless codecs) and then downgrade them, would most likely just use the high def tracks, since it has to read them to change them. What happens if that you keep the receiver from ever seeing an HD track. For a spdif connection, you set your BD player to output the lossy stream that coexists on DD TrueHD and that is the core of the DTS HDMA, so your receiver never sees a codec it cannot understand.

If you have an HDMI connection, the handshake between the receiver and the player will take care of this automatically . . .
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post #7 of 10 Old 12-01-2012, 10:43 AM
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7.1 processing has been around far longer than discrete 7.1 encoding. Like 20 years longer.

PLIIx, DD-EX, and Neo:6 all produce rear channel outputs from less than 7.1 sources. PLIIx generates stereo rears while the others produce a single rear channel that is fed to both speakers.

You can get excellent rear surrounds from 5.1 source content.

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post #8 of 10 Old 12-01-2012, 12:23 PM - Thread Starter
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My AVR doesn't have HDMI frown.gif. So the max amount of channels I'll get is 5.1... sad day...
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post #9 of 10 Old 12-01-2012, 12:29 PM
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Quote:
Originally Posted by KennyPa View Post

True but do I gain anything by having a 7.1 setup. If my receiver can't decode bluray audio tracks correctly.
Sure. With a well placed 5.1-speaker layout, there will be surround information that images closer to your left or right side and other sounds that will phantom image in between (appear to come from behind you). But this only works when you are sitting in the sweet spot. If you're not sitting exactly between your two surround speakers, then those sounds will collapse to the surround speaker closest to you, which is normal for phantom images.

However, if you extract the sounds that were going to phantom image behind you, and send those sounds to the speakers behind you, then their imaging becomes much more stable. You can be sitting anywhere on your couch and those sounds will always appear to come from behind you. No magic involved, just a pair of speakers placed behind you (makes it difficult for those sounds to appear from any other direction).

This is why some people prefer to listen to 2-channel music using 3 speakers: by extracting a centre output and sending that info to your centre speaker, those sounds (like vocals) always appear to come from their intended direction (middle of the soundstage) no matter where you're sitting. Same benefit for playing back 2 surround channels over 4 surround speakers: sounds at the left/right ends of the surround field stay at those locations and sounds inbetween/behind stay at that location, no matter where you're sitting. Same directionality, just greater imaging stability.
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Originally Posted by KennyPa View Post

Is Dolby Ex a 7.1 format?
No, Surround EX is 6.1 matrix surround format. The 2 surround channels contain some mono information that is exactly the same in both channels. With a 5.1-speaker layout, that mono information will phantom image behind you (with all the instability that phantom images have for off-axis listeners). If you have a 7.1 layout and apply EX decoding, then that mono information is extracted and sent to an additional pair of surround speakers behind you. Stereo information that was in the surround channels stays at the speakers along your sides.

So, 2 surround channels are decoded to 3 surround channels (left, right, back). You still get rear-vs-side imaging in the surround field, but the 2 rear speakers are run in dual-mono (since they're getting the same information).

If you have a 7.1-speaker layout, you're better off using Dolby Pro Logic IIx. The two rear speakers will each get an independent signal, allowing them to run as stereo instead of dual-mono. If you are listening to an EX encoded soundtrack, sounds that were supposed to come from both rear speakers will still be played back that way (dual-mono). But otherwise, you will hear sounds moving between those 2 rear speakers, as you would with any stereo pair.

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post #10 of 10 Old 12-01-2012, 12:41 PM
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Quote:
Originally Posted by KennyPa View Post

My AVR doesn't have HDMI frown.gif. So the max amount of channels I'll get is 5.1... sad day...
That's true as far as 7.1 source material is concerned, although there isn't much of that to begin with. With 5.1 source content, DSPs such as PLIIx work just as well with optical and digital coax connections.
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