How do Stereo Mixes Translate in Surround Capable Theaters?

Q

qwerty123

Well-known member
I've searched through a few books on post sound editing & mixing, as well as this forum, and I'm confused about how a stereo 2.0 mix gets translated into a theatrical environment that has 5.1 capability (with L,C,R, Ls, Rs, and Lfe).

To be more specific:

1. Let's say I'm printing my final mix in protools to a stereo track (in properly calibrated room with good levels, etc.)
2. I bounce to disk, and reimport into FCP7.
3. I then go into, say, Compressor and create a Blu-Ray with Dolby Audio 2.0
4. I deliver the blu-ray, and it gets screened at a festival which has 5.1 capability (and stereo obviously).

The question: how does the stereo mix translate into the L,C,R, and Lfe speakers (I'm assuming the surrounds don't even get touched)?

For example, my dialogue in the stereo mix is panned centered, whereas some FX aren't, etc. Will the dialogue simply go to the C speaker in the theater or will it also go to the L and R speakers as well? How about the FX?

This may be a stupid question, but it's a bit strange how books--especially those aimed at more low budget folk--don't really address this issue. I've looked at ones such as "practical art of motion picture sound" and two of jay rose's books.

Does it make sense to go for 3.0 (L,C,R)?
I don't have the budget, expertise, or time to do a 5.1 mix and don't plan on it.

But I'm wondering if it makes sense to, say, get one more speaker to do a 3.0 mix so I can properly understand how dialogue sits in relation to FX and BGs in a theatrical environment. Yes, I have the proper hardware to do 3.0.: mbox pro 3 in my case.

Thanks for any information on this issue!
 
It should just go the through the left and right front speakers .
Stereo is recommended film festivals and such. Festival 5:1 systems are rarely set-up properly and If the system is just stereo, the 5:1 down-mix can be really screwed up . Stereo is more fool proof. KISS.
 
Just to file away: you won't have a problem with stereo mix on a 5.1 system, but you will have problems with a 5.1 mix on a stereo system.
 
Probably you will have just a 2.0 through the front L&R speakers. They might run your mix through the "matrix" and that would put your L and R in the correct speakers, the centered sounds would get routed to the center speakers and the very low lows would get routed to the LFE. If you don't have any strange phasing going on (this mostly happens with music) then the surrounds won't have anything in them. IF you do have some phasy stuff in the mix parts may get sent to the surrounds.

You could check by decoding your mix through a ProLogic system and see if anything bounces to the surrounds. As I said this is almost always music that has some phase shifters or weird chorusing on it. If you do find things heading to the surrounds then making those sounds more mono will help.

Mono is the only real guarantee. Mono plays back as expected on every system. Plain stereo is pretty close but can have de-matrix issues, and 5.1 is a total crapshoot if you are not a big budget going into first class theatres. Even then it can be dodgy.
 
Thanks Noiz2 (and others).

Just to follow up a bit.

(1) I'd obviously prefer the 2.0 to be run through "the matrix." Wouldn't it sound weird to have only Left and Right speakers playing and no sound coming directly from the center of the screen? I'm thinking of venues where the screen is not just some small dinky thing, but movie theater sized screens (or close enough). Kind of like there'd be a "hole" in the middle?

(2) Is there a way--via some pro tools plugin or something--to simply do what the "matrix" does to produce a very basic 3.1 mix (assuming no phasing) based off of a stereo track? If not in pro tools, anywhere?

(3) Do you think it makes sense to get a third speaker for an L,C,R configuration for future mixing -- bearing in mind that this will be for low budget shorts and features.

Thanks for the great, fast feedback!
 
1) No. You will get a "phantom" center as you would on your stereo mixing set up. And you probably don't want to have them run it through the matrix unless you can check it out ahead of time. The first reason is that until you actually listen to it through the matrix you won't know if you have something flying into the surrounds or not. It's VERY distracting when it happens. The second reason is that virtually all 35mm films with optical tracks that have been matrixed (LtRt) have also been run through either Dolby A or Dolby SR noise reduction. Dolby A decoding isn't so bad but decoding through SR (tracks that were not encoded in the first place) will sound terrible.

We did a film with a LtRt and it was a nightmare for festivals. IF you are on 35mm no problem but in a digital format they are not used to running it through the matrix and it was a pain. Some couldn't do it, so while the matrix plays fine to stereo the Dolby SR sounds like crap un decoded. They ended up with three versions LtRt with Dolby SR, LtRt with out Dolby SR, and stereo. Only the first few festivals got the LtRt versions because they just caused to manny problems. Operators would forget to switch things over or would switch in the SR with a nonSR version or visa versa.

2) There is no 3.1 standard so... You can do 4.0 which is the LtRt (the 0.1 sub is just filtered from the main LR) but you have all the problems above.
And yes there are plugins and you can even find the Dolby converter boxes on eBay at times. If you are just checking then you can even just use a ProLogic decoder, it's the same matrix with out the noise reduction. BTW just using the decoder was often done in low budget shows that didn't have the $$$ for the Dolby license. Mix through the matrix decoder and you can kind of do a surround mix. You really will have a hard time getting stuff to predictably be in the surrounds but you can mix for the LCR front speakers and tune your bass to play well with the LFE extraction of the decoder.

3) only if you are planning on mixing in a surround format. Things may change, may already have changed? but very few festivals were set up to play surround off of anything but 35mm. DVD's don't look that good blown up os except for tiny festivals that wasn't a good choice. With BlueRay and DCP that should change, at least for festivals that are playing in theatres with high end digital projection. So?

It is a LOT more work to edit and mix properly in a surround format than stereo. You can take a stereo mix and fake a surround mix if necessary. There are expensive plugins that will do it but you can do a quick and dirty one.
L = L-R
R= R-L
C= R+L (may have to reduce by 3db to keep the balance correct)
Surrounds can be left empty or take a little of the L & R and send them through a touch of reverb to make the Ls & Rs
LFE = L+R but only material below 80Hz ( if you do this you should probably also filter below 80 out of the other channels.

This should produce a mix that sounds the same as your stereo (not counting the low splash in to the surrounds). It's not a real surround mix but a surround layout of your stereo mix.
 
Thanks so much Noiz2.

So here's another question I've just recently come across: I just got word that a film of mine is screening a decent / good festival. They have an exhibition form on which they ask how the film's sound is mastered (mono, stereo, 5.1 etc).

THEN, they ask: "If you are using stereo, would you prefer to be processed through Dolby Pro-logic?"

My hunch, based on this thread, is that I should say "no" -- but I'm a bit unsure. Thoughts anyone?
 
If you haven't checked your mix through a ProLogic decoder I would say NO.

It would probably be OK but you might get things flying into the surrounds and that is VERY distracting.
 
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