Ed O'Neill

7.1 Question..Help me figure this out.

Hi guys,

I have a Onkyo 787 and recently got in a disagreement with someone about 6.1 and 7.1. I have read that 6.1 is mono matrixed like pro-logic was. So please if you can help me figure it out I would appreciate it.

Now having said that.. my onkyo receiver says it is 6.1 (7.1 ready?)but they recommend in the manually to use it with two rear speakers instead of one,with an external amp.

He has some harman kardon receiver, I don't know the model of the top of my head.It has something called logic 7?

Here are the questions:

1. Is 6.1 matrixed meaning it is mono like pro-logic?
2. Is 7.1 a stereo version of 6.1 or is it still mono but with 2 channels like prologic was?
3. Is the harman kardon logic 7 thing- stereo to all channels(except the sub)?
4. If so are they the only company making 7.1 "all stereo"
5. If I use an external amp for my rears on my system would I be getting stereo?

Now...The most important question of all:
6. If all this is true about the logic 7 thing... How is it possible to get stereo sound to the rear speakers if the actual source(DVD) is only dolby digital EX mono to the rears?

BTW- I have read some stuff on harman kardan's site but don't get it that's why I made this post. So either I am wrong (confused) or he is misunderstanding his receiver capabilities.

Again please help me figure this out. I would really apreciate it.

Thanks in advance
Ed O'Neill

Chuck Kent

Ed: 1st, let me say how much I love your work on Married with Children and Dragnet (sorry, just kidding...I couldn't resist. I do like Ed's work!)

Well, I'll tackle your questions but one thing above all else is that there is no 7.1 in a consumer format. It's 6.1 with an extra rear center speaker.

1. There are 2 types of 6.1. 6.1 matrixed for DD-EX and DTS-ES. Then there is DTS-ES Discete that has a separate, discrete rear center signal. But in BOTH cases, it's a single, mono signal.

2. 7.1 refers to adding a 2nd speaker to carry the rear center signal. But both speakers carry the same signal.

3. Logic 7 is closer to Pro Logic decoding than it is stereo decoding. So no, it's not stereo to all channels.

4. No, 5.1, 6.1 or 7.1 all channel stereo is available on most receivers out today. The all channel stereo presentation is quite different than Dolby Pro Logic II or Logic 7.

5. No, as above, the rear center speaker is one signal.

6. Logic 7 may perform some kind of signal manipulation to gain a teeny bit of difference between the 2 rear centers. But the signal going in is mono.

You may still wonder why use 2 rears instead of one?? Some studies have shown that sound coming from behind us can be localized better if the source is coming from 2 closely spaced speakers versus just one. (I'm not convinced but the 2 speaker theory is the overall consensus.)

Hope this helps...

Kevin C Brown

I'll add some to what Chuck wrote.

1st, I always think of it as what the *source* is vs the type of *speaker system* the source is being played through. It is true that there are no 7.1 sources. There are only a few 6.1 sources: DD EX and DTS-ES. For DD EX and DTS-ES *matrix*, the rear channel is matrix derived from the surrounds. For DTS-ES discrete, that rear channel is discretely encoded into the soundtrack.

In *most* 7.1 speaker setups with accompanying processing, the 2 rear speakers signal are identical, meaning mono. However there are exceptions:

1) Logic 7. Logic 7 (quoted elsewhere) uses the steering available across the fronts to apply slightly unqiue signals to L & R rears. Non-mono. BTW, Logic 7 has different implentations. Lexicon is the best, and includes Logic 7 for stereo and 5.1 sources to get you a 7.1 soundfield. All H/K receivers (except for the 8000), only have Logic 7 for stereo sources: more like DPL-like processing, but still non-mono rears. The 8000 also has Logic 7 that can be applied to 5.1 digital sources, but it is not as tweakible as the version that's on Lex pre/pros.

2) THX Ultra2. Also non-mono rears, "decorrelated" whatever that means. (I think it's a small phase difference that's applied to the rears.)

3) The Rotel 1066 pre/pro with it's xS modes also get you non-mono rears.

One more example, just 'cause I'm familiar with it, the Outlaw 950 has CES modes which expand 2.0 through 6.1 sources for playback on a 7.1 speaker system. Mono rears, but nicely implemented.

If it's not worth waiting until the last minute to do, then it's not worth doing.

KevinVision 7.1 ...

Shawn Fogg

"6. Logic 7 may perform some kind of signal manipulation to gain a teeny bit of difference between the 2 rear centers. But the signal going in is mono."

That isn't correct. Logic 7 steers out 4 indpendant surround channels from 2 channel and 5.1 channel sources. You can have pans between the surrounds that goes from left side to left rear to right rear to right side. They are four seperate channels that can get different info between any or all of them.

Shawn

Chuck Kent

Just to clarify, it's still important to remember that the rear center signal from the source IS mono. It's a fairly safe bet that the channel separation of synthesized dual rear centers (no matter what the algorithm, Logic 7 or whatever) is still smaller than that of the other speaker relationships. Thus my comment of teeny (which I agree is not particularly scientific or objective...)

(One thing that would be beneficial for all of us...does Lexicon publish channel separation numbers for Logic 7 from channel to channel? Including the synthesized ones? Just curious.)

Shawn Fogg

"Just to clarify, it's still important to remember that the rear center signal from the source IS mono."

No it isn't because most sources don't have a rear center signal. In most cases Logic 7 doesn't ride on top of EX type decoding. It works on 2 channel sources directly (which have no rear center signal) and it works on regular 5.1 sources... which also doesn't have a rear center signal.

For two channel sources it isn't something like Cirrus Extended Surround on top of DPLII which is a matrix decoder riding on top of another matrix decoder. It is the one and only decoder working on the signal, and from it it steers out 7 channels.

In the MC-12 (and MC-8) Logic 7 can ride on top of DTS-ES 6.1 Discrete decoding and in that case it does take the rear center speaker and use that info to steer out the two stereo rears.

"...does Lexicon publish channel separation numbers for Logic 7 from channel to channel? Including the synthesized ones?"

They have said they haven't even bothered to measure it since it is a pointless exercise as it really tells you nothing about the ability of the decoder. How a matrix reacts on a single steady state test signal give no clue at all how it will react to changing dynamic signals. Going just for max channel seperation in a decoder will most likely cause other problems like pumping and breathing.

Having said that if it steers something to say left or right rear it is *easily* localized to that corner of the room, even when starting from a 2 channel source.

Shawn