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

[Fluffy]

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.

 

[polmuaddib]

I have an Atmos 7.1.4 with a b&w htm2 d2 for center channel. Overkill? Maybe.
I agree that in most cases you might not need a center channel and if you set your front L and R properly, you will have a perfect ghost center channel.
That said, there are some Living Stereo SACDs which are mixed in 3.0 (LCR) and some recordings benefit from that arrangement because there are early stereo recordings which had hard pans left and right and are awful to listen in regular stereo setup. They leave a big hole in the center.
Also, I listen to a lot of multichannel music and i prefer to listen to it in intended channel count. Could it all sound similar or even better without center channel? Maybe, but I like having it.

 

[Maconi]

From what I've seen, most rooms are way too small (the main listening position is too close to the speakers) to allow the speakers to properly blend naturally. You'll usually have very obvious separation without the center. Even then there are usually tricks used (with room correction, EQ, delays, phasing, etc.) to help increase the illusion of one giant sound stage.

 

[Chrispy]

Maybe if only worried about one seat the phantom center may work well enough. That said, have tried both ways and I prefer a center. Then again I think 2ch stereo was a compromise in the first place, and difficult to sell/implement 3ch originally.

 

[HemiRick]

In most multichannel mixes the dialogue is sent to the center channel, to me it's clearer and easier to hear the dialogue w a center channel speaker. Yes while it is possible to use the 2 mains, I find this way less enjoyable.

 

[Fitzcaraldo215]

Have you read Toole’s book? In it, he makes a cogent point about HRF affecting frequency response near the center of our heads. It is not so at frequencies nearer to the sides.

As a really dedicated Mch fan, I think that it is paramount to get a center channel, suitably integrated to the side channels. Have you tried it? In carefully controlled listening tests, aside from the the frequency response issues, I am hearing more depth and dimensionalty in the center of the soundstage.

But, I am listening to music at the 90% level via SACD or BluRay. I watch the occasional BluRay videos and I am sure that what ever pertains to music, pertains to video,

 

[Kal Rubinson]

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

For the same reason you need it in a stereo system. It is essential for the proper recreation of centrally placed voices and instruments.

 

[North_Sky]

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.

Maybe because it's more solid, more three-dimensional, better anchored, following the onscreen action ... car passing by, actor's voices following directions, like old Cinerama movies. Like Frank ...

 

[blackmetalboon]

I ran a 4.0 system for a number of years which worked well as long as I was sitting in the sweet spot. Eventually I managed to get a matching center speaker which really helped when I’m not sitting centrally between the front left and right speakers.

 

[RickSanchez]

Maybe because it's more solid, more three-dimensional, better anchored, following the onscreen action ... car passing by, actor's voices following directions, like old Cinerama movies. Like Frank ...

Looking at the coffee table in that picture, is that a ginormous bowl of .... cigarettes?

 

[Chrispy]

Looking at the coffee table in that picture, is that a ginormous bowl of .... cigarettes?

Pic from a cigarette ad?

 

[Bear123]

A center channel produces sound from the center better than the left and right speaker do, regardless of where you sit. 2 channel is not optimal, just a handicapped and well known format left over from the dark ages.

Also, its unrealistic to think that only one person sits dead center at all times for movies or listening to multichannel music. Anytime someone is not dead center, the L/R do an even worse job of anchoring sounds to the center.

 

[SynthesisCinema]

Some claims has been made for Kef speakers with the coaxial UniQ driver design doing better the "phantom center" as the sound won´t change as dramatically if one moves from the middle. Thoughts?

From article: Without a center speaker, the center channel is mixed in stereo and distributed between the front left and front right speakers. The sound level is reduced to half (-3dB) in order to deliver the original signal at the right volume with two speakers. This is where things get tricky, and if the audio engineer decided to further reduce the sound level during the downmixing process (maximum reduction of -6dB), then the amplifier will have to comply with this obligation.
https://blog.son-video.com/en/2018/...system-you-may-be-losing-more-than-you-think/

 

[Kal Rubinson]

Some claims has been made for Kef speakers with the coaxial UniQ driver design doing better the "phantom center" as the sound won´t change as dramatically if one moves from the middle. Thoughts?

Perhaps but it cannot change the position of the speakers and their relationship to the HRTF.

 

[North_Sky]

Looking at the coffee table in that picture, is that a ginormous bowl of .... cigarettes?

I'm not sure I cannot make it exactly. I posted that photo for the center channel below the TV set in Frank's room. And I like Frank's voice ...

Pic from a cigarette ad?

I don't think it's a cigarette add or they would clearly indicate the brand.
It's only a photo of Frank's 3-channel hi-fi stereo sound system...high fidelity music reproduction from three mechanical/electrical loudspeakers.

And Frank was an analogue music lover...open reel-2-reel tapes.
...Jazz easy listening singer and avant-gardiste audiophile.

 

[Blumlein 88]

Testing going at least back to the 1950's show when 3 recorded channels are used, you get better accurate portrayal of position, depth and location with a center channel than if you blend it to a pair of stereo speakers even with the listener centered. Sometimes movies record this way, and usually are artificially creating something that isn't real. So the remaining advantages for movies is for dialogue and off center listening. With MCH music the advantage of the center is still very real.

What I found using MCH movies/TV shows in both a stereo setup and a 4 channel setup for several months was the following. Sometimes the center from stereo is pretty good, and sometimes the way it gets downmixed makes it very hard to distinctively understand. When using a 5 channel source with down-mixing to 4 channels of speakers I found the same result. On some work the center was good enough not to be a bother and in others the downmixing greatly reduced clarity. So use a center channel and you'll prevent such problems.

 

[andymok]

https://en.wikipedia.org/wiki/Surround_sound

The function of the center channel is to anchor the signal so that any central panned images do not shift when a listener is moving or is sitting away from the sweet spot.[27] The center channel also prevents any timbral modifications from occurring, which is typical for 2-channel stereo, due to phase differences at the two ears of a listener.[24] The centre channel is especially used in films and television, with dialogue primarily feeding the center channel.[25] The function of the center channel can either be of a monophonic nature (as with dialogue) or it can be used in combination with the left and right channels for true three-channel stereo. Motion Pictures tend to use the center channel for monophonic purposes with stereo being reserved purely for the left and right channels. Surround microphones techniques have however been developed that fully use the potential of three-channel stereo.

See also
https://en.wikipedia.org/wiki/Center_channel

https://www.sweetwater.com/insync/center-channel-surround-mixing/ (long article)

Its primary function is to provide hard center anchoring for key components (such as dialog in film postproduction, or lead vocals or solo instruments in music) with greater stability than phantom centering, and without any of the comb filtering problems that occur with phantom centers.

I was also told that, in a large setup such as cinema, the Centre channel helps compensate and provides stereo image to the seats on both flanks

 

[Senior NEET Engineer]

Problem I have with center channel speaker is that I can't place it optimally while also placing the TV optimally.

Is there any benefit to center if I'm just upmixing from stereo? The sound image is already uncannily sharp and vivid.

 

[zuli]

Some claims has been made for Kef speakers with the coaxial UniQ driver design doing better the "phantom center" as the sound won´t change as dramatically if one moves from the middle. Thoughts?

I do have Kef speakers, and I can tell you that the center channel is needed, because if you are not in the center for the phantom image, you are hearing the dialogues from one speaker only, and this is strange.

 

[mrjktcvs]

With a center channel speaker, I can adjust the trim by a couple of db on my system so the voice track can stand out from an aggressive music track being sent to the front mains.