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Dolby Digital EX...5.1/6.1?


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16 replies to this topic

#1 of 17 OFFLINE   Brendan D

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Posted July 20 2004 - 06:46 AM

Can't seem to figure this out....I was on Dobly's website...it lists DD EX as adding a additional speaker, effectively providing for a 6.1 environment. However, I have several DVD's listing specifically DD EX 5.1 Surround Sound. What is the difference? The DD EX 5.1 (Return of the King, for example) does not engage the surround back speaker. So why is DD EX 5.1 any different from DD 5.1? Thanks for your help.

#2 of 17 OFFLINE   Michael Reuben

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Posted July 20 2004 - 07:31 AM

DD 5.1 and DD 5.1 EX have the same number of discrete channels: five (left, right, center, left surround, right surround) plus a Low Frequency Effects channel. However, in DD 5.1 EX, additional sounds are matrixed into the left and right surrounds that are intended to be extracted by a Prologic-type decoder and sent to a center back channel. Because there is no new discrete channel being added, the format remains 5.1.
It's a common problem, because a DD EX 5.1 track has to be properly flagged for the receiver to turn on EX processing. If you know that the disc has EX encoding, just engage it manually. M.
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#3 of 17 OFFLINE   ChrisWiggles

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Posted July 20 2004 - 09:52 AM

As noted, that 6th channel is a matrixed channel, not a discrete 6th channel (except in the case of DTS-ES discrete). If the disc is not flagged correctly, or your receiver is not going into EX mode (you need to have a 6th speakerat least, dual rears are preferred in a 7.1 array to eliminate the potential for the reversal effect) then you can just engage EX/ES processing manually.

#4 of 17 OFFLINE   Ted Lee

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Posted July 20 2004 - 10:50 AM

what's the reversal effect?
 

#5 of 17 OFFLINE   ChrisWiggles

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Posted July 20 2004 - 10:55 AM

Ted, the short of is is that placing a speaker directly on-axis behind you head causes some psychoacoustic difficulties. Your hearing acuity is worse behind you (turn around and try to image stereo behind you, it is much worse than from the front). As a result, having a speaker directly behind you, your brain can confuse those sounds as coming from in front, instead of from behind, and so things can get a little weird sometimes. As such, everyone, DD, DTS, THX, Lexicon, etc all recommend using 7.1 speaker arrays instead of just adding one rear speaker. Even if those are wired together in mono, it is preferred. Added processing that creates stereo rear backs can be even better, but the consensus is that you'd like to avoid a 6.1 array of speakers if possible, or maybe use something like a dipole behind you that will be more diffuse and will image better behind you.

#6 of 17 OFFLINE   AndreGB

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Posted July 20 2004 - 04:38 PM

Chris, are you talking about the null effect? Is it the opposite of the reversal effect?

#7 of 17 OFFLINE   Ted Lee

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Posted July 21 2004 - 06:02 AM

thx chris...never thought about that but it does seem to make sense.
 

#8 of 17 OFFLINE   ChrisWiggles

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Posted July 21 2004 - 07:39 AM

the "null effect?" Not sure what you mean by that, nulls are acoustical occurrences that occur due to reflections in the room mainly with bass, etc. Multiple speakers will also affect this if you have multiple subs, for instance, but nulls and peaks are acoustical phenomenons.

#9 of 17 OFFLINE   AndreGB

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Posted July 21 2004 - 09:50 AM

Oh, I thought the null effect was the one obtained from using the dipolar speakers. So that the audience don't sit right in the axis or something like that. Maybe I was wrong.

#10 of 17 OFFLINE   Ted Lee

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Posted July 21 2004 - 11:15 AM

on a dipole speaker, the "null" is the part that faces you (i think...) maybe that's what you were thinking andre???
 

#11 of 17 OFFLINE   AndreGB

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Posted July 21 2004 - 12:00 PM

Maybe Ted. Thanks a lot. Posted Image

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#12 of 17 OFFLINE   ChrisWiggles

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Posted July 21 2004 - 01:14 PM

Yes, dipoles work by being out of phase and creating a null due to the multiple drivers working out of phase.

#13 of 17 OFFLINE   Robert P

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Posted July 25 2004 - 07:13 AM



#14 of 17 OFFLINE   Michael Reuben

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Posted July 25 2004 - 09:18 AM

No they're not. They contained matrixed information for a rear center channel, but the left and right surrounds are discrete, regardless of whether EX decoding is being applied. M.
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#15 of 17 OFFLINE   PeterK

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Posted August 02 2004 - 09:32 AM

So if you use DD 5.1 ex how do you wire in the 6th/7th speaker to the two existing surround speakers. if you have the 7 speakers do you wire both back chanels to both surrounds or just left to left, right to right?
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#16 of 17 OFFLINE   AndreGB

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Posted August 02 2004 - 11:23 AM

As far as I know, if you are using EX then the two rear surround will output the same channel. Though they are connected on their respective outputs on the receiver (which are discrete), I mean, you don't wire the two speakers together.

#17 of 17 OFFLINE   ChrisWiggles

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Posted August 02 2004 - 03:52 PM

EX/ES receivers will have either 6 or 7 outputs, and 6 or 7 amps. Sometimes the 2 rear backs will have different connectors, but off one amp (like the mono surrounds from many old PL receovers). Mine, for instance, has 6 outputs, and I physically wire two speakers off the rear for a 7.1 array. Some that have 7 amps and outputs will also have additional DSP such that those two are in stereo. Your manual will explain your receiver's capabilities in more details, but in any case, a 7-speaker *array* is preferred.




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