Why do we need a center channel in a home theater system?

[Vasr]

Steinberg, J. C., and Snow, W. B. (1934). Auditory perspective-physical fac- tors. Transactions of the American Institute of Electrical Engineers 53(1), 12-17. (Behind paywalls), cited, amongst others in https://www.harman.com/documents/HowManyChannels_0.pdf

Yes, that is the same Bell Labs study I mentioned above and my comments hold. It was in the context of establishing a strong central location cue for off-center viewers not to be used as support for necessarily adding a center channel for a central viewer.

To summarize:
If you have multi-channel AV content, a dedicated center channel would be highly recommended for a number of reasons including wider seating arrangement with center localization (as suggested in the Bell Labs study). It could be a central single speaker or a phantom center with dedicated speakers at the edge of the screen which additionally can give greater flexibility of adjusting the screen stage to the virtual audio stage (without adversely affecting L and R imaging).

If you have multi-channel audio-only content, then a well-balanced L and R is sufficient. The potential downside is that the downmix done by the device/player in such a case may not truly reflect the intent of the multi-channel mastering due to down-mixing volume decisions (to avoid clipping). In general, using the number of speakers corresponding to the number of channels in the content would be the best approach.

HRTF based algorithms are more useful in the different situation of maintaining a virtual multi-channel sound stage with synthesized surround from 2-channel or down-mixed multi-channel content when lesser number of speakers are available (for example, into headphones). Not to be confused with the above considerations.

 

[JoachimStrobel]

Yes, that is the same Bell Labs study I mentioned above and my comments hold. It was in the context of establishing a strong central location cue for off-center viewers not to be used as support for necessarily adding a center channel for a central viewer.

To summarize:
If you have multi-channel AV content, a dedicated center channel would be highly recommended for a number of reasons including wider seating arrangement with center localization (as suggested in the Bell Labs study). It could be a central single speaker or a phantom center with dedicated speakers at the edge of the screen which additionally can give greater flexibility of adjusting the screen stage to the virtual audio stage (without adversely affecting L and R imaging).

If you have multi-channel audio-only content, then a well-balanced L and R is sufficient. The potential downside is that the downmix done by the device/player in such a case may not truly reflect the intent of the multi-channel mastering due to down-mixing volume decisions (to avoid clipping). In general, using the number of speakers corresponding to the number of channels in the content would be the best approach.

HRTF based algorithms are more useful in the different situation of maintaining a virtual multi-channel sound stage with synthesized surround from 2-channel or down-mixed multi-channel content when lesser number of speakers are available (for example, into headphones). Not to be confused with the above considerations.

Reading the summery from Toole gives me a different impression. Instead of
„If you have multi-channel audio-only content, then a well-balanced L and R is sufficient.“
It reads
„ So, two-channels were understood to be a compromise, “good enough for the home” or words to that effect, and what did we end up with? Two channels!“

And that is what we are arguing about. Sure, sure, one can get away with two channels which is just good enough, and earlier in Toole, it reads for economic reasons.
If we are arguing here about the lowest economic case for good Mch, then I am all behind „two speaker is enough“.

 

[usafa77]

I recently replaced my multi-driver tower main speakers with single-driver coaxial ones. I was running the same center channel speaker (one of the MTM horizontal types) in both setups, located one shelf below the TV. I never had very precise vertical imaging with the towers, and the wide vertical imaging of the center channel speaker (due to its orientation) didn't help matters. However, I was even less thrilled with the overall imaging using the new speakers. I fiddled with the new speakers' height and placement and toe-in, and adjusted various settings in the preamp, but none of this made much difference. It just didn't sound right. Then one day I was playing around with the remote control's buttons and selected the preamp's "stereo" mode. Voilá. The vertical audio image fell into place, and the horizontal image sounded "sharper" and deeper. So, I went into the preamp configuration and deactivated the center channel, and then listened in multi-channel mode again. Much better overall sound than when the center channel was engaged, and vastly superior to when the towers were in place. I = happy camper.

So am I saying that a center channel is superfluous? Absolutely not. What I am saying is that no center channel at all can be better than a misplaced, misoriented, and mismatched one. Duh. A no-brainer, right? Of course I knew that, but maybe too often we keep redressing the pig instead of just acknowledging that the pig is ugly. And, frankly, MTM speakers laying on their sides are ugly in any clothing.

I will reinstate a center channel to my system, but it will be a coaxial one that lives better with the new mains. I should have done that in the first place. Even before I got the new speakers. Oink, oink.

 

[Andysu]

Why do we need a centre channel or why do we need a Left-Centre Right-Centre channels?

I use a inner left-centre right-centre channels to give a wider stage thou the room is small I can still detect the half-panned sound effects or maybe music and yes directional dialog panning using two matrix decoders connected to the LCR with some Y leads and connecting to two matched decoders and when switched on with classic movies such as, Ice Station Zeba, The Towering Inferno, Logan's Run, Indiana Jones and the Last Crusade, or even Gravity that holds the best directional dialog of any movie and still yet hasn't be surpassed not even by disney star wars.

The speakers thou typical would be spread wider apart in and this case they are mutual coupled partly acts as baffle so I only need few little wood or other placed between gaps to make it like a baffle wall. Rest of the speakers behind the screen some are storage of the other JBL HF horns JBL 2371 which I used for some years and sounded okay but the step-up with JBL 2380A in my view is better sounding too bad not enough space for JBL 2360A but that would mean I would have to go back to using three-screen. I prefer five-screen and I can use the Dolby SDU4 switches to send if I want Music playing in stereo on Left-centre Right-centre by selecting MONO on the SDU4 cos each Left and Right goes to two seprate decoders therefor can play as mono or stereo depending on the source material. If I select Stereo mode on the decoders my common LCR will be used. If I select Dolby Surround on the decoder then five-screen will then be activated for use.

Also there is a bonus with the decoding as I never intended it to be I sort of came across it and then realized ? Hey that is rather neat. When I select the decoders for mono and I can still play the movie as Stereo LR with centre phantom but here is the bonus. If I adjust the AVR centre it will lower or decrease the centre phantom. Try doing that on any other AVR/AVP thou it is relativity easy to wire up just got use extra outboard equipment.

I use two Dolby SDU4 1U frame the rack has recently been changed so many times.

Decoder at top is for Left ch, left-centre and centre / decoder below it is for, right-centre and right. The back of the decoders using XLR balanced inputs/outputs that are then connected to the x2 Sony SDDS DFP-D3000 cinema processors then then outputs connected to two Behringer MDX4600 then connected over to the Behringer DCX2496 then onto the amplifiers to the screen speakers.

I used my DLSR with fish eye lens, usually use the canon wide lens.

So why do we need it? I like it. I like how it sounds and sounds exciting would be ideal if my room was larger but I managed to test it and get to fit and work within a very small room for a 120" screen.

 

[Vasr]

Reading the summery from Toole gives me a different impression. Instead of
„If you have multi-channel audio-only content, then a well-balanced L and R is sufficient.“
It reads
„ So, two-channels were understood to be a compromise, “good enough for the home” or words to that effect, and what did we end up with? Two channels!“

And that is what we are arguing about. Sure, sure, one can get away with two channels which is just good enough, and earlier in Toole, it reads for economic reasons.
If we are arguing here about the lowest economic case for good Mch, then I am all behind „two speaker is enough“.

Sufficient in the sense of a SINAD in the 90s being sufficient. regardless of price.

L-C-R might give a different stage perception than L-R (particularly for off-center listeners if that is the use case of concern as in these studies) but none of them necessarily support doing so for a single MLP or with no visual cues. This is the main point. It doesn't discourage someone from using a center channel as long as the implications are understood.

Given the variability of room and speaker distances in a typical setup, putting a center speaker isn't going to magically reproduce some mastering intent nor is it necessary for enjoying the content. Just number 3 isn't a panacea that will necessarily make it better. This is my main disagreement.

Putting a center-channel speaker isn't a no-brainer proposition whose only costs are economic. It isn't easy to match a center speaker with L and R unless it comes as a matched set from the manufacturer (it may not be so even if they say so for marketing reasons) and even then you would need to ensure that they are matched in phase, volume, dispersion, etc. Very few of them are true center point sources. Its efficacy would also depend on the distances between L and R and between the speakers and the listeners and might even result in a bad stage image if not set up correctly or the practical limitations of the room dictate sub-optimal placement. So, is it worth the trouble for audio only? Not in my opinion. YMMV.

A lot of this is similar in discussion of using a separate sub rather than just L and R. There are pros and cons and the answer depends on the context. This is why I have tried to separate out the needs/context. Between AV and Audio only content. Between center listeners and off-center listeners. etc.

 

[rccarguy]

First of all, I want to say that I'm currently running only a stereo setup, so this is mostly an academic discussion. Not looking for setup solutions or upgrade suggestions.

What I want to understand is, why do we need a center channel in a surround system in a home?

As far as I understand it, the function of a center channel in the cinema theater is to "anchor" the dialog (and other centered sound effects) to the screen, so that wherever an audience member sits, they will perceive it coming from the middle of the screen. If there was no center speaker and the dialog would be mixed as a ghost center image produced by the front left and right speakers, someone sitting off to the side of the theater would have the center image all screwed up for them.

But in the home, if you put up a descent surround setup, most likely you will sit in the center in front of the screen. In that case, you don't really need a speaker located physically on axis with the screen to center the dialog. The center ghost image of the front stereo speakers would work just fine, just like it works for singing in music (when mixed to a centered mono).

I don't suppose anybody believe you need a dedicated channel to produce sounds that the other front speakers are "too busy" to produce, right? That would be absurd. And front speakers with a nice flat response would produce dialog that would be just as intelligible as one that comes from a dedicated speaker. No one complains about unintelligibility of singers when played in just stereo, right?

So what's the point then? The center channel seems to me like a vestige from how it works in the cinema, imported to the home without any real necessity.

You're not going to get confirmation from me that a center speaker is not ideal in home cinema.

 

[JimA84]

First of all, I want to say that I'm currently running only a stereo setup, so this is mostly an academic discussion. Not looking for setup solutions or upgrade suggestions.

What I want to understand is, why do we need a center channel in a surround system in a home?

As far as I understand it, the function of a center channel in the cinema theater is to "anchor" the dialog (and other centered sound effects) to the screen, so that wherever an audience member sits, they will perceive it coming from the middle of the screen. If there was no center speaker and the dialog would be mixed as a ghost center image produced by the front left and right speakers, someone sitting off to the side of the theater would have the center image all screwed up for them.

But in the home, if you put up a descent surround setup, most likely you will sit in the center in front of the screen. In that case, you don't really need a speaker located physically on axis with the screen to center the dialog. The center ghost image of the front stereo speakers would work just fine, just like it works for singing in music (when mixed to a centered mono).

I don't suppose anybody believe you need a dedicated channel to produce sounds that the other front speakers are "too busy" to produce, right? That would be absurd. And front speakers with a nice flat response would produce dialog that would be just as intelligible as one that comes from a dedicated speaker. No one complains about unintelligibility of singers when played in just stereo, right?

So what's the point then? The center channel seems to me like a vestige from how it works in the cinema, imported to the home without any real necessity.

I think you could probably do quite well without the obnoxious center channel except it's kind of forced on you by the fact that content producers want to use it.

I hate it because it's so difficult to place in a home theater scenario with available products and furniture.

With a conventional system I would place it angled upward about 10° or so under the center of the TV. Good luck finding furniture with the dimensions to accommodate that without custom manufacture. There is some, but you have to look hard to find it.

People who make furniture are clueless.
They want to stuff a thousand watt receiver into a tiny unventilated box and put a weight bearing center panel in the middle where the center channel speaker needs to live.

If anything they expect a yuppie soundbar, not a high fidelity speaker.

The other challenge is that some speaker designs simply can't be adapted to that mounting position.

If I was using Newform Research Last Dance Nanos for the center they really need to be mounted vertically.

Thus the best way might be to mount them on stands immediately to either side of the TV and wire them in parallel.

The Nanos are about twice the impedance of the larger models, so this would end up with a center channel well positioned and impedance matched.

Thus mounting the center channel is also dependent on the speaker architecture.

Either horizontal underneath the TV or mono wired on either side in parallel.

In the case of the Newform Research Nano ribbons this works out to the same impedance of the larger models, so its not an issue.

The problem with the center channel is that most equipment makers are clueless about making one that is practical and can be installed in a reasonable location.

 

[Sal1950]

I think you could probably do quite well without the obnoxious center channel except it's kind of forced on you by the fact that content producers want to use it.

Not really forced on you, modern receivers will do a good job mixing center info into L&R speakers and in most cases will
be just fine unless speaker spread is very wide or listening positions are way off center..

Biggest issues I found was with furniture and needed room for the larger quality centers under the TV. In my case I was able to mix & match the poles from another system to gain height and also custom included a center support all the way to the floor so the heavy 85" big screen didn't cause the top shelf to sag. My JBL HDI 4500 is tilted up to aim at the MLP.

 

[Peterinvan]

I am enjoying my Onkyo 2.1 stereo amp with two speakers. I get a nice soundstage image.

HOWEVER… when I watch Netflix, if the movie is streamed at 5.1 or higher, I have to go to the setup and switch off 5.1 (select English Original) in order to hear the dialogue properly.

 

[Sal1950]

HOWEVER… when I watch Netflix, if the movie is streamed at 5.1 or higher, I have to go to the setup and switch off 5.1 (select English Original) in order to hear the dialogue properly.

That's odd ???