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Discussion Starter · #1 ·
I was reading all about Dolby Stereo.

What I find strange is the center channel.


No where in "history" does one explain why a center channel.


I remember it was supposed to "fill" in the center with mono sound, only when the left and right speakers were too far apart.

Has this somehow become a standard?


Then Dolby surround sound uses a "center" channel in the rear, for I believe delay sound to image a large theater.

Then if you have a Dolby 5.1, it uses the left and right (side) speakers together for the surround sound effect. I believe they used to be rear left and right speakers, but now they are put on the sides.


Then 5.1 is the "true" stereo, with 5 discrete channels.

If this is true, isn't the center a mono version of the front left and right?

So we are back to 4 channels.

(yes, I know, the .1, is the real low frequecies of the front left and right to give more low "effects")


Then the new 6.1 or 7.1 is just the .1 channels made for the rear.


Does this also mean there will be a 8.1 with an added center channel in the rear?
 

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Discussion Starter · #2 ·
What I am questioning is, Is there a real use of this center channel?


Is it just the mono version for the center?

Or is it delayed slightly to give a "reverberation" effect for "concert hall" sound effects?


Somehow it just seems to be taken for granted.
 

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Ideally, the recording engineer will place unique information on the center channel that isn't contained on either the left or right (or at least not on both) channels. In that case, it isn't just a derived channel from the front stereo channels, but a truly independent channel (discrete).


If we got everything we wanted, we'd have twenty channels in an array around us in a dead room, and recording techniques that could capture the information coming from different directions due to hall reflections and such in the recording venue (or, from very sophisticated processing applied to studio recordings). Sadly, people still seem to think "stereo" is better. :(
 

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For me, the purpose of the center channel is to anchor the dialog to the center of the screen for people who sit off axis. When I watch movies by myself or with one other guest, I turn off the center and I get better results.
 

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Discussion Starter · #6 ·
I guess, I was thinking that if you sat in the middle, and sound came out from both left and right front, it would appear in the center.

But, if you are sitting off to the right and left, the center would then be a benefit..


Still, I can't not see the use functionally, for the center speaker.


The idea is to make the sound come from, or to appear to come from the direction it was made.

This can all be done with 4 channels.


And if you sit off center, you do not get the "true" realism of the sound, because it has been designed for the "sweet point" or middle of the sound speakers.


The only reason I can come up with is that in evolution, we had mono, then 2 ch stereo, and then to get more "concert" type of sound, separating the left and right so far, that a center was used for a fill.


Recording engineers can put something in the discrete center, but why?

Just because it is there?


I do believe they do this to "CHANGE", SO to keep people buying new.


First 2 ch stereo.

Then 3 ch, 2 ch plus center.

Then 4 ch front and rear left and right

Then add a "sub woofer" or LFE and put it all together for 5.1

Now move the rear to the sides and add a rear LFE.

we get 6.1

then add 2 rear LFE, which is the same rear channel for 7.1


We do know what is next, left and right rear. Do we call this 8.1 next year?
 

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George, believe it or not, when stereo was added to hi-fi mono, there were three channels, not two. The main full-range speaker stayed in the middle, where it was to begin with, and a pair of satellites was added to play the difference signals that made the stereo image.


The move to eliminate the center speaker was perhaps begun by someone's wife who complained about the quantity of boxes cluttering the living room. It was discovered that a phantom center could be derived from a pair of full ranges as long as one stayed centered in the 'sweet spot'.


Remember that home theater was a long way off when theater theater sound became multi-channel. Fantasia was a four-channel movie when it was new. The center speaker for theater came along later, when wide-screen movies came out to draw the new television crowd back to the theater.


There was a need to have the center-of-the-screen action and dialog emanate from the center of the screen, especially for those seated to the sides. Star Wars started the real surround fervor. (By the way, Fantasia was never a widescreen movie, so don't expect to see it accurately that way.)


Anyway, to continue, there was quad sound, which was a four-corner matrixed and/or discrete fad that only lasted a couple of years, but never had a center channel. And even when Dolby stereo came into the home, the center channel was an option, and even then was matrixed, not discrete.


I had one of the first surround receivers made, the Pioneer VSX-5000. The center channel was merely an RCA jack for external amplification. In other words, there were three channels, left, right, and mono surround, but often 'de-correlated' by a phase swap or other means.


Anyway, the point of all of this is that your timetable is a little off.


First, there was mono.

Then, 3-channel stereo.

Then 2-channel stereo.

Then 4-channel quad.

Then 3-channel Dolby.

Then 4-channel Dolby.

Then 5.1-channel DD.

Then 6.1-channel matrix.

Then 6.1-channel discrete.


The whole idea of a second rear speaker came about because of the phenomenon that a single speaker behind the head sounds like it could be anywhere in the middle, above, in front, etc., the same way a mono sound in stereo headphones sounds like it's coming from between your ears instead of in front of you.
 

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The center channel was eliminated since there was no media that would support three channels. Vinyl (aka records) could only record two tracks, not three.


The 'phantom' center was well known to the researchers ... as well as all the problems with two channel playback.
 

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Discussion Starter · #9 ·
So I guess, the center channel is mainly for theater, where there is a large space between the left and right.

Yes, now I know it has become a discrete, but it probably is a mute point if it is matrixed or discrete for the home system.

But, as now I know, they are recording the center channel as a discrete, which answers my question.

Thanks.
 

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Larry,

I was the engineer of a small recording company that broadcast John McLaughlin and the Mahavishnu Orchestra live in Quad from the Whisky A GoGo in Hollywood in....1972? 73? "LA's First Live Quad Broadcast." At that time, there was rivalry between Sansui and some other company as to who would better "encode" four discrete channels into two that could be decoded with quad audio amps....I have never had A SINGLE CLUE as to how or why the Sansui was the better unit, but it was!


Anyway, you missed one generation of surround there. Someone at Dynaco added front center and rear center channels to stereo this way:


1)The left and right speaker hots were connected to the left and right amp hot leads; those speakers' ground leads were connected together.


2)A center speaker was wired from those speakers' ground leads to the ground of the two power amps (the amps had to have a common ground).


3)A rear speaker was wired from the plus of one amp to the plus of the other amp. A variable resistor was added in series with the speaker to keep it from being too loud and lowering the overall speaker impedance too much.


And:


1)The left and right speakers performed pretty much as before. There was probably 3 to 6 dB less left-right separation.


2)The center speaker was fed the current going through both left and right speakers. Signals equal in phase therefore were stronger in this speaker than in either the left or right speaker; sounds equal in phase correspond to front, so there was your front channel. Left and right signals came out together here, too, but at least 6 dB lower than the left and right speakers. Yeah, separation was lousy but the effect worked!


3)Audio from the plus of one amp to the plus of the other amp was audio that was out of phase from one channel to the other. Sounds from the rear generally have this characteristic, and it sounded right to put this speaker in the back.


This wiring played hell with the amp loads, and had to be done carefully with bulletproof amps to play very loud. I blew out more than a few 2N3055s with this setup.


Most anything by Pink Floyd LITERALLY was all over the room with this setup. It was better than most surround you hear today because it seemed like they had this in mind when they mixed their stuff.


Soon it became obvious that the phantom center was good enough and that center speaker was a pain, so Dynaco took the front speaker away. They marketed a box, though, about a six inch cube with a volume control and a switch, that wired two speakers between the two amp hot channels, and messed with their separation via an adjustable resistor to ground. They basically hooked two speakers from hot to hot, but put a 10 to 40 ohm variable resistor between the amp ground and a point between the two speakers.


I worked at Rogersound Labs at that time. We made speaker systems and sold audio gear. The owner and I and a customer owned that recording company I mentioned, and we did everything in discrete quad, so we were interested in quad. I worked out a serviceable quad circuit that fit in about a four cubic inch box. It was just terminal strips, a DPDT stereo/quad switch, and two 20 ohm ten watt resistors. I still have a couple of them. I think we called them instaquad, and indeed we gave them away to sell speakers.
 

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Then of course,


There exists...


Q Stereo Listen to R. Waters, Amused to Death CD

7.1 Matrix - several brands

8.1 Matrix - (actual 6.1 discrete) Yamaha (Effects/Height channels)

Then there is the rare DD 10.2 Matrix found only in in custom istallations.

Plus whatever Circle Surround calls it tech.

& of course as usual I probably missed some...


Dynaco:

"little box" = a Q10, it had a null switch that killed the L&R info & dialed in the difference between the R&L & put that MONO channel to the 2 rears.

It is called a Hafler Circuit.

If you used their pre amps or combo's I.E. SCA80Q nothing ever blew.

Pink Floyd's mixes - YES!

You should also hear/watch Aliens on one of those systems! I only really changed it at the 5.1 stage, the sound fields held until then.
 

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Discussion Starter · #12 ·
So, as of now, the 5.1 is the default standard (?)

But we are getting into 6.1 matrix and discrete, and 7.1.

I assume all will or can be decoded into 5.1 ?


Of course there are 3 types (as far as I know) of sound:

1) Music

2) Movie

3) Games


each with a little different (or extra) type of decoding.
 

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George,


RE: So, as of now, the 5.1 is the default standard (?) Yes - Good phrasing


RE: But we are getting into 6.1 matrix and discrete, and 7.1.

-6.1 discrete is available only in a FEW DTS recordings.

-Dolby has added EX which is 5.1 with extra surround/side channel info in a

FEW titles.

- Not that I'm the top source, but I haven't come across a definitive

statement/commitment that DD is moving to 6.1. However, I have seen

an inference that they are exploring Height Channels.

- 7.1 Matrix only - haven't come across anything in 7.1 Discrete yet.

- 8.1 Matrix a few companies are using that as well I.E. Yamaha (height

channels)


RE: I assume all will or can be decoded into 5.1 ? - Yes
 

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You left out Ambisonics (UHX matrix) and Ambisonics Discrete (none I know of in commercial release). Ambisonics also has height information capability in the specifications. This has been around for along time. I have about 400 CD's in UHX.


Height information will be a part of whatever it is that will be the next 'standard'. I suspect it will get down to 10.2 or Ambisonics as being the two leading candidates. 10.2 has Holman behind it and it fits well into what Yamaha has been doing for years. Ambisonics has been around for along time, has both discrete and UHX (matrixed) formats. So who's to know?
 

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George.


RE: Height Info.: Think of regular 5.1 Discrete - each speaker being given its own directed information. Then think of a separate array of speakers mounted up near the ceiling (2 for Yamaha) or on, or in the ceiling going from front to rear, side to side & those speakers only reproducing those sounds which would be found overhead in a natural setting. Therefore, the sound of a helicopter flying overhead from front to rear, would originate in the front L,C,R speakers, then be picked up & reproduced in the overhead (height) speakers, from the front overheads moving to the centre overhead(s) moving to the rear overheads, then finishing in the rear centres. Probably the side surrounds would be involved. There are those around who are using a 5 overhead setup - 2 front, 1 centre & 2 rear overheads.

FYI, some are playing with floor/ground effect speakers also. Height channels/speakers (& floor) are only at best also Matrix at this point.


Then of course you can add shakers in your floor &/or couch!!
 

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I cant imagine anyone questioning the use of a centre speaker. Its a complete necessity in any hoem theatre even with plain old dolby surround.


It is a completely seperate channel designed for any action that happens central to the sound stage. so if a sound moves fromleft to right it passes through the centre speaker. also most dialogue tends to come from this unit.


If it was not there people voices would sound out of proportion and would seem to come from far too wide an area. even if you were able to set up your mains to focus exactly only 1 person would ever enjoy that effect.


The centre has nothing to do with the size of a room or to fill in a blank space its just 1 part of a set of discrete channels. Without it a cinema or home cinema sound system tends to lose focus and precision and sometimes voices prove very hard to understand.


Definately not something to be missed out on.
 

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Discussion Starter · #19 ·
Shrink;

Age

I believe older people will ask "why ?"

We don't take hype as fact.


If you can't answer why, then there is something to think about.
 
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