True HD and DTS Master audio 7.1 mixing? - AVS Forum
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post #1 of 8 Old 12-12-2012, 11:52 AM - Thread Starter
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Hello All,
This maybe a stupid question, but when an audio engineer or in the case of a Movie the re-recording engineer mixes an audio portion of a movie in 7.1 how are the additional 2 channels utilized. I know that in a 7.1 set up you can either use 2 front height speakers or 2 side speakers. If the engineer wanted the additional sound effects to appear that they are coming from the sides of listening area, what would happen if I used 2 front height speakers instead of 2 side speakers? Wouldn't this totally mess up the intended sound stage?
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post #2 of 8 Old 12-12-2012, 01:10 PM
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7.1 is front three, side (surround) and rear speakers. The other things are new fangled stuff that you will NOT find anybody has mixed. The height or wide channels have to be generated by software in the receiver. No movie has been mixed with discrete wide or height channels wides or hight AFAIK., and the multimillion dollar stages they mix on, AFAIK, don't have wides or heights.

Although as I understand it, there are experimental/proposed systems, like Sonos (i hope I'm remembering the name right), that use more than 5 or 7 main channels, but they're compertely different, and not widely implemented and you'd need steering to route from the 300 plus speakers in a full Sonos system to our measley 7.1s anyway.
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post #3 of 8 Old 12-12-2012, 01:26 PM - Thread Starter
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Hello,
Ok thanks that makes more sense. So when they mix the 7.1 it is the side surround channels that are added. More of a 360 degree experience. I already get this from my 5.1?
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post #4 of 8 Old 12-12-2012, 05:16 PM
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Quote:
Originally Posted by HeffeMusic View Post

Hello,
Ok thanks that makes more sense. So when they mix the 7.1 it is the side surround channels that are added. More of a 360 degree experience. I already get this from my 5.1?

No. when they mix 7.1 it is the back surrounds that are added. Side surrounds are the "surrounds" in a conventional movie theater . . . 5.1 is with surrounds (at the sides).
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post #5 of 8 Old 12-12-2012, 06:56 PM
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Quote:
Originally Posted by HeffeMusic View Post

So when they mix the 7.1 it is the side surround channels that are added.
As JHAz alluded to, it is the back channels that came later. Though it's a bit more complicated than that.

When you hear a 5.1 soundtrack in a typical movie theatre, each surround channel is copied to an array of surround speakers that go up the side wall AND cover half the back wall. Since the sound for each surround channel comes from your sides AND partially behind you, it's not really fair to say that surround channel info is intended to come from your sides, because it comes from both directions.

For 5.1 in a home theatre, folks tend to place their single pair of surround speakers along the side walls, sometimes a little rearward of the seating location to get a compromise between side and rear directionality. Hence the notion that those sounds are supposed to come from the sides.

When 'Star Wars: Episode 1: The Phantom Menace' was being mixed, sound designer Gary Rydstrom wanted to have surround information exclusively behind the audience (for things like flyovers) without those sounds also appearing at the sides. So they added a third surround channel: the surround-back channel. With 'Toy Story 3', the surround-back channel went stereo and theatres updated to 7.1 channels.

So surrounds came first, then a mono surround-back channel, followed by stereo surround-back channels. I guess you could think of it as having side channels first with rear channels added later, but I think a more correct explanation is that over time surround channel were eventually split into side and rear parts.
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Originally Posted by HeffeMusic View Post

More of a 360 degree experience. I already get this from my 5.1?
As much as you might be satisfied with your system and believe it to give you a 360 degree experience, understand that a single pair of surrounds can't be in two places simultaneously: at your sides AND behind you at the same time.

The only way to get stable imaging at your sides and behind you is by having speakers at both those locations. Plus there are other advantages, like more precise directionality (rather than some side-ish/rear-ish location) and greater wrap-around envelopment (4 speakers can literally 'surround' you better than 2 speakers could).

So if you're happy with your 5.1 set-up, no need to change. But let's not pretend that adding more speakers doesn't have advantages, especially when it comes to imaging stability. For example, if you want stable height imaging, the easiest and best way to do that is by simply adding speakers above you. Same with adding a second pair fo surrounds and going to a 7.1 set-up.

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post #6 of 8 Old 12-12-2012, 07:13 PM
 
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been reading the op thread. Very interesting, so what if a user doesn't have rear surrounds? and has an option for "Virtual Surround Back" ? 

i never try'd it, but will it simulate rear channel? 

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post #7 of 8 Old 12-14-2012, 12:49 AM
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I've never heard of a "virtual surround back", but I suspect it's like those virtual surround modes that stereo speakers often use to try to simulate a surround experience. I would believe it's not as good as true surround back speakers, but might work okay in certain rooms.

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post #8 of 8 Old 12-14-2012, 07:17 AM
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In my experience it seems that the novice HT user may not read instrution manuals before mounting or hooking things up. I have known at least 6 ppl that have or had 5.1 setups and they had their surrounds mounted on the rear wall. I guess side speakers didn't make sense to them or whatever the reason for it. A few of these ppl have updated to 7.1 and added side surrounds and I just had to make sure they connected the speakers correctly to the new 7.1 receiver.

I have a very modest system compared to a lot of ppl on this forum, but to me its a good setup. My friends and family think I'm nuts and spent way too much money on this stuff. They even think that the cheap $300 to $500 HTiBs from a brick and mortar store are more than overkill for in a home. But some of these same ppl have Corvettes, boats, snowmobiles and other such expensive toys so to each is own.

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