The Centre channel: what signal gets sent to it? How demanding compared to Left and Right?

[Newman]

Do you have a home theater set up with 5.1 or even more speakers?

If so, unplug your center channel and try watching some TV and some movies clips. That will definitely give you some insight.

Yes that is a good point that you, and some others already responding, are making. I have done it for brief experiments, and heard nothing that made me think that centre channel has to be 'more muscular' than left and right.

But instead of my very limited personal trials, I was interested in anyone with a grasp of the bigger picture.

The comment made about centre channel carrying gunshots in movies made me think. That would be demanding.

 

[MarcT]

Until you listen to 3 way center with 6.5 woofers.

Yes, my center speaker is a Polk LSiM 706c, which is a large three-way with two 6.5" woofers. It does pretty well, but still does not reproduce a deep voice as well as I'd like.

 

[Newman]

Mains that do mids/voices incredibly well with rock solid imaging completely negate the inclusion of a compromised centre. In fact I have half a dozen centres lying around that only get used as test speakers for repairs on my bench- I gave up listening to centres a very long time ago- they would all make me cringe.

My 5.1 has the same 3 JBL 5" monitors across LCR

 

[flyzipper]

If so, unplug your center channel and try watching some TV and some movies clips. That will definitely give you some insight.

This is not an equivalent test to achieve the phantom centre approach that @restorer-john is discussing.

If your AV processor is configured to use a centre channel speaker, and it's simply disconnected, you'll definitely miss key aspects of the surround mix.

If, however, you configure an AV processor to operate without a centre channel speaker, the centre channel content will be mixed into the left and right channels to achieve a phantom centre image.

I'll echo the comment that phantom centres are preferable to using an inadequate centre, or when proper centre channel speaker placement isn't possible due to the use of a TV (rather than an acoustically transparent screen + projector) -- especially if you don't need to accommodate multiple listening positions.

 

[Newman]

Responding to a few posts about 'crappy' centre speakers:

To be clear, my OP is in no way meant to suggest I thought a 'crappy' centre would be OK.

It's just the idea that it needs to be better than left and right that I am exploring.

 

[Blumlein 88]

Here is Til Death do We part. Same center channel preponderance of sound.

 

[Newman]

What about music that has been recorded in multichannel?

 

[Blumlein 88]

Episode 2 of Heels TV show. Also preponderance of center channel signal.

 

[Blumlein 88]

Here is Heels Ep2 again with a spectrogram view and the center and LFE channel expanded.

 

[MarcT]

Episode 2 of Heels TV show. Also preponderance of center channel signal.
View attachment 171926

This info about the preponderance of the center channel info are very helpful. Is there a way to look at the low frequency extension and level in the center channel signal in movies or TV shows?

 

[Blumlein 88]

What about music that has been recorded in multichannel?

Daphis et Chloe from BIS in surround FLAC. Looks like LCR are nearly equal in level and BIS didn't use the LFE channel. Actually the center is kept about 3 db below left and right as I measure these.

 

[Blumlein 88]

This info about the preponderance of the center channel info are very helpful. Is there a way to look at the low frequency extension and level in the center channel signal in movies or TV shows?

See the post above yours. Center has many of the below 100 hz signals of the LFE (though not all) while the LFE looks to be set for 100 hz and less.

 

[Blumlein 88]

This a Mozart 5 channel recording from 2L music. All 5 channels have near equal level in this. And they do use the LFE channel just a bit.
Looking at a few more 2L tracks I have they appear to all be put together in the same way as this one.

 

[dasdoing]

surround channels do include echo like sounds of dialog at low levels

Do surrounds even make a substantial diference while watching a movie? I have wondered a while if having those makes sense to me who watches a movie like once a week

 

[MarcT]

Do surrounds even make a substantial diference while watching a movie? I have wondered a while if having those makes sense to me who watches a movie like once a week

I think it just depends on what you want. I have tower speakers for my surrounds and run them full range. In some action movies, I get a lot of loud deep bass content from them. For dramas or comedies, I could do without the surround channels.

 

[Blumlein 88]

Do surrounds even make a substantial diference while watching a movie? I have wondered a while if having those makes sense to me who watches a movie like once a week

Yes I think they do. Some are mixed different ways than others of course, but while lower in level they do give a much larger sense of space. Plus in some scenes off picture sounds are placed there and sound much more real than if they were mixed into the front channels.

One example I recall is in The Blues Brothers, when the jilted fiance blows up their hotel building. They have lots going on in the surrounds in this scene. It totally transforms the sound field to have surround vs stereo in this particular example.

Here is the scene though you won't get surround on youtube.

 

[MarcT]

See the post above yours. Center has many of the below 100 hz signals of the LFE (though not all) while the LFE looks to be set for 100 hz and less.

Lol, I did see that post, but I don't know how to interpret it!

 

[Sancus]

Here are the 6 channels from Loki episode one. A movie with plenty of explosions and such in all the channels.
Order is L, R, C, LFE, left surround and right surround. In general terms of energy the center channel has the most going on.
Despite how it looks, the analyzer function shows the average level for the right and left tracks are only 3-4 db lower than for the center track in this one instance.

Yeah this is pretty much how every tv/film show will look. If you actually solo the center and compare it to the left/right during action sequences, you'll probably notice that the sound effects are spread across all 3 channels but the center has the loudest portion of them on average in addition to the dialogue.

It's a bit different for music, which is all over the place. Typically the center is not the loudest channel, but it's often used to carry center vocals. It's rare for it to be louder than the L/R like film/tv, but it is often equal to them. Then again, there are also cases where the surrounds have more content than the center, like Pink Floyd's The Dark Side of the Moon.

Arnesen - Fecit Potentiam(track 5) from 2L Magnificat:

Spoiler

Christopher Tin - Mado Kara Mieru - 5.1, this piece has center vocals mainly in the center with only vocal reflections/reverb and instrumentals in the L/R.

Spoiler

BTBAM - The Great Misdirect - Swim to the Moon - 5.1

Spoiler

Pink Floyd - Dark Side of the Moon - Time(Track 4) - 5.1

Spoiler

This is why I believe the correct way to build a multi-channel system is to pick the center first, and then everything else based on the best center you can pick given your size constraints. There is absolutely no point to having big floorstanders paired with a wimpy 2-way center with 5" woofers, unless your intent is mainly just to use them for stereo music.

If you are being very serious about a multi-channel system then everything that isn't a height channel should be capable of close to the same output.

As far as the "well just phantom center" theory goes, I think that's fine if you only care about one seat and you accept that stereo can't produce a timbrally correct center image, but it's suboptimal. If the alternative is having your whole system bottlenecked by a wimpy 4" tall center though, then yeah, that's probably the right way to go.

 

[Blumlein 88]

Lol, I did see that post, but I don't know how to interpret it!

Well it is a spectrogram view. Basically a running FFT. On the left is the frequency axis, and intensity is shown by the color of the graph. Grey or light blue is low in level, pink, red and bright red are highest in levels. So for the LFE channel you can see it is empty above 120 or 150 hz. Does that make sense?

Maybe more involved than you want, but how to view a spectrogram.

Understanding Spectrograms

Learn how a spectrogram works, how to use one to examine an audio file, and how to fine-tune the type and amount of information presented in the RX spectrogram.

www.izotope.com

 

[Alice of Old Vincennes]

Yes, my center speaker is a Polk LSiM 706c, which is a large three-way with two 6.5" woofers. It does pretty well, but still does not reproduce a deep voice as well as I'd like.

It should. Guess you need the Revel 3 way beast!