[TSD444]

I've been doing a lot of thinking about sound design lately, and now Im wondering about possible ways to improve the center Channel. The idea that Ive come up with involves spreading out the center channel into multiple speakers if you have an abnormally large screen. In my case, Im working on my design for a 12' wide anamorphic screen, so the thought occured to me that a single center channel speaker might not be enough to compensate for a screen so large - especially considering that voices originate from more than just the center of the picture.


I have to imagine that commercial theater designers have thought about this themselves, and Im curious to know what others think. I know that our minds work to match up sounds to images, but could we improve upon the center channel by spreading it out over a couple more speakers?

 

[Wrager]

I know multiple center speakes are generally fround upon due to several issues around comb filtering and wave coherence etc. A really big screen may use multiple center speakers that are tightly controlled for horizontal dispersion.

 

[TSD444]

Ok, so it would seem like there is a lot more to this than just placing a couple more speakers behind the screen to spread out the sound more. I suppose that as long as we don't have multiple center channels, then the main thing is just to make it so that the dialogue seems to be originating from the screen. I've read a couple of articles talking about how wide a single vertical speakers sound can spread, and that would seem to be fine for a small theater, but what about localization? If you had a couple more speakers to either side of the main center, then that would seem to me to prevent anyone from noticing that the dialogue is only coming from the center of the screen.


Does dialogue ever come out of the right or left front speakers, or are they only used for sound fx and music?

 

[krab]

Since it seems you want more dialog, go for it and add more center channels.


But, make sure the crossovers in the centers have the correct and matching resistors and capacitors so the dialog frequencies dominate.



I just did this using 2 Def Tech CLR 2000 centers with help from Jeff at Sonic Craft.


This made a huge difference, the dialog is much more discernible in both bluray and HDTV.

 

[TSD444]

Why does the comb filtering and wave coherence present an issue in this case? How exactly would having multiple vertically oriented speakers cause a problem in a reasonable small theater where the listeners would never be more than 30% off axis?

 

[SoundChex]



Quote:
Originally Posted by TSD444 /forum/post/18125635


. . . could we improve upon the center channel by spreading it out over a couple more speakers?

The SDDS movie theater layout is 7.1, and has five front speakers. As does the 22.2 channel/speaker layout ['inspired' by the forthcoming(?) SHV/UHDTV] embraced by SMPTE 2036: Front Left, Front Left Center, Front Center, Front Right Center, Front Right (FL, FLc, FC, FRc, FR). But it seems likely you'll have to wait until around 2015 (or maybe later!) to make use of them, when we start to we get receivers with the necessary upmix/downmix/remapping functionality included...?!

 

[TSD444]

For years now I've had this idea in my head that 24.8 (speakers corresponding to every wall and corner on 3 levels, plus corresponding floor subs) would be the "ideal" surround sound system, but now I'm thinking that if your attention is going to be focused on a screen in front of you, then the majority of the speakers should be there as well. Question remains though as to how acute our sense of sound is in regards to localization. Even if movies could be mixed for multiple front channels, would it really be all that beneficial?

 

[bluesky636]



Quote:
Originally Posted by TSD444 /forum/post/18126095


Does dialogue ever come out of the right or left front speakers, or are they only used for sound fx and music?

Watch/listen any movie where the actors walk on/off screen while speaking or are speaking to someone off screen. Also watch/listen when they are at opposite sides of the screen and are talking to each other. You will hear dialog from the far left/right as well as dialog that is off center due to being mixed into both the center and left/right speaker. This is nothing new.

 

[TSD444]

I thought that the dialogue for movies was mixed to take advantage of the front right and left channels, but I wasnt sure. If that is the case, then the argument for multiple, discrete, center channels becomes weakened unless you have a very large screen/it bothers you that all of the dialogue is coming from a single point on screen.


Even if multiple, discrete, center channels are not necessary, I still think that there could be a case made for just multiple center channel speakers spread out behind the screen to insure that dialogue isnt localized to just the center. If your going to go through the trouble of placing speakers behind a large AT screen, why not make sure that you do it the best that it can be done?


I'm still concerned though about the issue that Wrager raised in regards to the comb filtering and horizontal dispersion - are they legitimate concerns? What other reasons may you not want to add a couple more center channel speakers?

 

[jcgeny]

i did that with a 5 speakers kit from jamo : the S 506 HCS 3 . i use the s 506 as back speakers , the S 50 CEN and s 502 are connected using "Screw terminals" on the center speaker line of receiver . i will put the power them on when i get my x+fi soundcard in a week or two . that should be great

 

[Dennis Erskine]

Where did you get the idea that the center channel was only for dialogue?


If you add more "center" speakers to clean up dialogue or because you have an imaging hole between the center and left, and center and right speakers, or your sound stage does not extend outside the boundaries of the room, you have an acoustics problem, potentially a speaker problem, or both.

 

[TSD444]

Ok, so it looks like I'm not the only one who has ever thought that it might be an improvement to spread your center channel sound out across your screen, but why wouldnt you want to?

 

[TSD444]



Quote:
Originally Posted by Dennis Erskine /forum/post/18127565


Where did you get the idea that the center channel was only for dialogue?


If you add more "center" speakers to clean up dialogue or because you have an imaging hole between the center and left, and center and right speakers, or your sound stage does not extend outside the boundaries of the room, you have an acoustics problem, potentially a speaker problem, or both.

I never said that the center channel was only for dialogue, but it's primary purpose could be said to reproduce human speech.


The possibility of an imaging hole is at the heart of the matter here. Yes, I am concerned that with a larger screen a single speaker might not have a wide enough dispersion to cover the audience, but more so I am concerned about localization of the center channel speaker. Characters do not just speak from the center of your screen, so my thought was that if you had multiple, discrete center channels, then you would have a more realistic/immersive presentation.


Even without the addition of discrete center channels, I still think that it would be an improvement, if you have a large enough screen, to have a couple more center channel speakers to spread the audio out so that it doesnt seem like all of the dialogue etc. is coming from the center of your screen. Does anyone know how commercial theaters handle this issue?

 

[GregLee]



Quote:
Originally Posted by TSD444 /forum/post/18126095


Does dialogue ever come out of the right or left front speakers, or are they only used for sound fx and music?

Switch your receiver to Dolby ProLogic II Music mode to get more dialogue from the front speakers. There is also an adjustment, "width" I think, to control how strong this effect is.

 

[William]



Quote:
Originally Posted by TSD444 /forum/post/18127353


...I'm still concerned though about the issue that Wrager raised in regards to the comb filtering and horizontal dispersion - are they legitimate concerns? What other reasons may you not want to add a couple more center channel speakers?

Here is a decent article about audio comb filtering .

 

[William]



Quote:
Originally Posted by TSD444 /forum/post/18127353


...I'm still concerned though about the issue that Wrager raised in regards to the comb filtering and horizontal dispersion - are they legitimate concerns? What other reasons may you not want to add a couple more center channel speakers?

Here is a *decent article about audio comb filtering .


Keep in mind it's in relation to stereo (or 5.1) discrete channels and not referring to multiple mono or same source channels (which is what you want to do in the center) .

 

[craig john]

You're trying to solve a problem that doesn't exist. There is no imaging hole. Sounds can image between the CC and the L or R speakers by using phantom imaging similar to the phantom center image created with just 2 stereo speakers. The mixer simply mixes the sound between the CC and either the L or R channel and the listener hears a CC/L or CC/R phantom image. You don't need extra speakers in the CC to spread the image out.


In my system, when sounds "pan" across the front soundstage, they pan smoothly without "jumping" from speaker to speaker. This includes dialogue. If someone is speaking while they move across the screen, the dialogue moves with them smoothly, without holes or stutter:

It doesn't matter how big your screen is. The sounds are mixed to image appropriately with the 3 front speakers.


Craig

 

[TSD444]

It's good to know that either through the original mix, or via additional processing, that movie dialogue can be spread around the front speakers. I still wonder about localization though, but perhaps I am over thinking this. If our minds work to match the images were viewing with the sounds were hearing, then perhaps this isn't an issue for reasonably sized home theaters, but Id still like to know how a commercial theaters behind screen speakers are set up.

 

[GregLee]



Quote:
Originally Posted by TSD444 /forum/post/18129893


If our minds work to match the images were viewing with the sounds were hearing, then perhaps this isn't an issue for reasonably sized home theaters, ...

It's an issue for me. For both the home theaters I have, the sound stage is much wider than the screen is, and the disparity is often jarring. My screens are 42" and 50" TVs.

 

[TSD444]



Quote:
Originally Posted by GregLee /forum/post/18130010


It's an issue for me. For both the home theaters I have, the sound stage is much wider than the screen is, and the disparity is often jarring. My screens are 42" and 50" TVs.

I hadn't given much thought to how normal sized screens might have the reverse issue to deal with. I figured that the conventional way of placing speakers around a screen wasn't ideal, but I also just assumed that people just took the good with the bad.


I wonder how we could limit the size of our sound stage so that it would better correspond to how we want it for normal sized screens. What if we were to install speakers around the frame of a tv so that you would have two center channels imediately above and below the screen, and then the left and right speakers immediately to either side. Would this help to control the audio imaging for normal sized screens?