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

[sarumbear]

Except Im not a seller and have no vested interest in buyer other than to help them sort through options and optimize a multi-variable decision.

Im all about the value of perspectives and fine with disagreement but attacking the motives with implied financial gain considerations is a non-starter.

If you are not a seller who is the "we" in your words below?

The buyer will later spend more money upgrading..it's what enthusiasts do. Thus, we want to support the smoothest upgrade path.

 

[sdiver68]

If you are not a seller who is the "we" in your words below?

Experienced enthusiasts offering collective perspectives and advice.

 

[sarumbear]

Experienced enthusiasts offering collective perspectives and advice.

I apologise misunderstanding your motive. I am an experienced enthusiast and I think your advice is bad. Maybe you can consider not to assume that everyone will be agreeing with you and omit the word "we" in your future posts.

I disagree that there should be an upgrade path like that. An upgrade path is for instance to start with five channels then go up to seven channels. A centre speaker is part of every theatre standard, home or cinema. Without a centre speaker you have a miss-configured theatre sound system. Your advice is technically wrong

 

[sdiver68]

I didn't assume anything. In fact, I laid out the exact parameters under which I made my conclusion.

Just like the technical papers you rely on to judge my advice as "technically wrong" are making assumptions such as:

ITC BS.775 : Multichannel stereophonic sound system

The following requirements are related to the specified multichannel sound system with and without accompanying picture.
1 The directional stability of the frontal sound image shall be maintained within reasonable limits over a listening area larger than that provided by conventional two-channel stereophony.

2 The sensation of spatial reality (ambience) shall be significantly enhanced over that provided by conventional two-channel stereophony. This shall be achieved by the use of side and/or rear loudspeakers.

It's up to the buyer to determine which of those parameters/assumptions apply to them.

 

[flyzipper]

Do please re-read. That is for the LFE channel, not through bass management, i.e. the subwoofers are fed only from the LFE channel, LCR, etc. are not send to them.

There is a section about bass management to be used if the low frequency of the speakers are limited. However, it clearly qualifies what limited means; "all speakers' response should extend from 40Hz at the low frequencies..." (2.5.2). How many small 2-way speakers you know that can go down to 40Hz? In other words contrary what you think, Dolby does not accept the use small 2-way bookshelves.

View attachment 175293

For some reason, the other clip didn't appear in my original post...

I don't think we're saying anything that's fundamentally different, it just sounds like we have different design objectives (you're happy with 40Hz, and I want 20Hz).

If the design objective is 20Hz, a speaker that extends to 40Hz is still, "using speakers with limited low frequency response", and I choose to not miss an entire octave by ignoring system response between 40Hz and 20Hz, so subwoofers are required (and part of the Dolby spec). Others will look at my 20Hz goal as ignoring the octave between 20Hz and 10Hz, and I'm fine with that. We all draw a line somewhere.

 

[sarumbear]

If the design objective is 20Hz, a speaker that extends to 40Hz is still, "using speakers with limited low frequency response", and I choose to not miss an entire octave by ignoring system response between 40Hz and 20Hz, so subwoofers are required (and part of the Dolby spec). Others will look at my 20Hz goal as ignoring the octave between 20Hz and 10Hz, and I'm fine with that. We all draw a line somewhere.

You don't have to miss the bottom octave. Just use speakers that can reproduce it instead of relying on bass management. Section 2.5.1 is fall-back, not the main specification. Why use the fall-back method?

 

[sarumbear]

It's up to the buyer to determine which of those parameters/assumptions apply to them.

Obviously it is but the advise should be to use the standard. Why do you think standards exist? Do you personally think you know better than experts behind those standards and decades of cumulative experience?

 

[sdiver68]

Obviously it is but the advise should be to use the standard. Why do you think standards exist? Do you personally think you know better than experts behind those standards and decades of cumulative experience?

I know how to interpret standards and then presented them for other to validate or disprove. You are making an incorrect interpretation which I've shown using your own preferred technical reference.

 

[sarumbear]

I know how to interpret the standards. You are making an incorrect interpretation which I've proven using your own technical reference.

There is nothing to interpret. It is clear as a bell. Use wideband LCR speakers at the front. If you can't and as a fall-back, use bass-management but make sure LCR speakers works down to at least 40Hz.

End-off!

 

[sdiver68]

End-off!

Agreed, it seems nothing productive can come from this line of discussion.

 

[audio2920]

Without a centre speaker you have a miss-configured theatre sound system. Your advice is technically wrong

That's a bit strong for me. Most stuff comes down to preference at the end of the day.

If music replay is important (as stated in point 6) I can totally see a case for dividing a finite budget differently than just "divide by number of speakers" even to the extent of ditching the center.

Would I run HT without a center channel? Probably not. But is there ever a case for doing so? Almost certainly IMHO.

 

[sarumbear]

That's a bit strong for me. Most stuff comes down to preference at the end of the day.

Will it be called correctly configured stereo set-up if one speaker is placed at the front and the other at the back as some folks do?

 

[Newman]

…or if you put one speaker on the left ear and the other on the right ear?

 

[audio2920]

Will it be called correctly configured stereo set-up if one speaker is placed at the front and the other at the back as some folks do?

Not for me, no, because the panning is messed up in that scenario.

I'd say having a speaker in the wrong place is generally worse for mix translation than not having it in the first place - but again maybe that's preference?

I'd rather listen in 2.0 than 7.1 with the center channel hanging off to the side or something silly.

In theatrical Atmos we mix with L,Li,C,Ri,R behind the screen, then when we go to the Home Atmos mix there's only LCR. It doesn't usually break the mix by removing the inner screen speakers. And I feel removing the center channel is just an extension of this. It's not ideal, but it's better than having C poorly positioned.

As I've said, personally, I probably would have LCR as a minimum for HT, assuming it's physically possible. I'd accept the lower speaker quality resulting from "budget divided by 3" than "...by 2".

But I can totally see why an owner/retailer/installer might advocate spending the majority of the speaker budget on LR and forget about the rest, especially so if the system is likely to have a high percentage of music of use.

 

[sarumbear]

Not for me, no, because the panning is messed up in that scenario.
[...]
But I can totally see why an owner/retailer/installer might advocate spending the majority of the speaker budget on LR and forget about the rest, especially so if the system is likely to have a high percentage of music of use.

Wrong placement of speakers on a stereo setup or a lack of centre speaker on a HT setup are both the same: a misconfiguration. You are happy with one, but not happy with the other. You have a preference to correct panning, I have a preference of vocals following the screen. Specifications are created so that you don't have to decide what is right and what is wrong. I don't think i is not our place to decide which part of the specification is needed and which part is not.

 

[Newman]

You have every right to think whatever you want, however I respectfully disagree. Even though it is pretty odd to think that almost all recording and mastering studios equipped with crippleware sound systems. Bass management is a solution if your speakers are not capable, or if you don't want to use acoustically treat your room, or don't use powerful EQ. It is just a cheap solution.

You have every right to think whatever you want, however I respectfully disagree. Recording and mastering studios are equipped with a range of compromised setups to simulate real-world listening scenarios, so I don’t worship false idols. Best placement of treble and midrange speaker drivers are in different locations to bass drivers, so ‘capable’ speakers are modular. Sufficient acoustical treatment involves a 2m thick full width and height wall of filling on the front or back wall, plus one side wall, plus the ceiling. Good luck. ‘Powerful EQ’ of bass from 2 integrated speakers placed optimally for mid and treble reproduction will never match the inherent smoothness from 3 or 4 optimally placed subs, plus severe risk of overloading the amp, and the room itself, from desperate but unnecessary attempts to compensate for poor placement.

 

[sarumbear]

Recording and mastering studios are equipped with a range of compromised setups to simulate real-world listening scenarios, so I don’t worship false idols.

Can you point to some examples, please? I have never been such a studio.

Best placement of treble and midrange speaker drivers are in different locations to bass drivers, so ‘capable’ speakers are modular.

Can you tell me us a few examples of such a "modular" speaker make/model?

Will you consider a Revel Salon2 an uncapable speaker?

Sufficient acoustical treatment involves a 2m thick full width and height wall of filling on the front or back wall, plus one side wall, plus the ceiling. Good luck.

I don't need luck. I know enough to design rooms that have correct acoustics (and your dimensions are off the charts). My rooms and the sound systems work pretty well together with a little help from EQ.

 

[audio2920]

Wrong placement of speakers on a stereo setup or a lack of centre speaker on a HT setup are both the same: a misconfiguration.

I get your point that Dolby would say you need LCR. And I can't say you're wrong - 4.1 for example isn't (AFAIK) a valid Atmos config.

I kinda feel like we're having an argument when none exists though. I too would rather follow spec and have a center channel than not.

We're only talking about when compromise has to be made and specs can't be adhered to for whatever reason. At this point it does absolutley fall on the end user to decide what they can and can't achieve from what Dolby (or others) require. While it's not for me, I am not against the idea of running without a center if there's good motivation to do so.

When I make Atmos or 5.1 mixes, 2.0 compatibility is checked so (discarding the surrounds folding in) I pretty much know how my mixes will play without a center.

And yes, you're right it's a preference, but placing the LR pair with one at the back of the room is absolutely going to be more distracting to me than having no center channel with LR correctly placed.

 

[tecnogadget]

So this turned from a center channel discussion to a multichanel layout normative one ?

Just follow whatever the international standar says (ITU BS.2159-8 [07/2019]) and you can always make little cm/angle degree changes based on preference or special cases (difficult rooms), there is no more to it.

 

[flyzipper]

Will you consider a Revel Salon2 an uncapable speaker?

It's a great speaker, but it depends on the requirements in order to assess whether it's capable, or not.

If the design objective is reaching THX refence levels at 20Hz, the Salon2 would be incapable of that (on its own).

THX calls for speakers to be capable of 105dB peaks, and subwoofers be capable of 115dB peaks -- at the listening position.

Factors that were considered are the Salon2's published specs of 86.4dB@1m efficiency and -6dB@20Hz, plus factoring in a reasonable listening position that's likely 4m rather than 1m. Doubling the distance reduces SPL by 6dB according to the inverse square law, so factor a -12dB attenuation should be applied based on doubling the 1m distance twice, and then granting a 3dB bonus because there are 2 sources.

My math says that's about 8000 watts to coax 115dB of 20Hz energy at a 4m listening position, but as speakers they'd only need about 500watts to reach the 105dB objective for those frequencies.

watts	efficiency	4m distance -12dB	two sources +3dB
1	86.4	74.4	77.4
2	89.4	77.4	80.4
4	92.4	80.4	83.4
8	95.4	83.4	86.4
16	98.4	86.4	89.4
32	101.4	89.4	92.4
64	104.4	92.4	95.4
128	107.4	95.4	98.4
256	110.4	98.4	101.4
512	113.4	101.4	104.4
1024	116.4	104.4	107.4
2048	119.4	107.4	110.4
4096	122.4	110.4	113.4
8192	125.4	113.4	116.4
16384	128.4	116.4	115dB target

All that said, if one or both of them are positioned such a 20Hz null exists at the listening position, then this goes from incapable to impossible... and illustrates the point that was made earlier -- that optimal speaker position isn't always optimal for producing bass, and that subwoofers are useful tools to keep in our audio toolboxes.