Axiom Home Page Forums General Discussion Home Theater 7.1 vs 5.1 install

Now, I have speaker wire ran to every imaginable place. So thats not a problem. What is a problem is my understanding of 5.1 vs 7.1. So here are some questions -

1. How many movies are now in 7.1? How do you identify those?

2. If I have a 7.1 setup (with the suggested two mon speakers, center back) how will 5.1 sound? Will the receiver up-convert to 7.1?

3. Does it make sense to run Front R&L, Side R&L, Rear R&L and Rear Center, since I will have some movies in 5.1 and some in 7.1?

Also, how does HD and television sound come through? Say you are watching the superbowl which is in HD....is that 5.1? In a 7.1 setup, how does the sound change? how does the sound get re-routed to the other speakers (or does it?)?

Thanks!

1. 0, I think. There are 6.1 movies, id'd as Dolby Digital EX and DTS ES or something along those lines.

2. If you put the reciever in certain modes, it will upconvert to 7.1. If you run it in pure DTS or DD, it will not (AFAIK).

3. No. You'll need a front center!

5.1 is Front L, C, R, + side L & R + sub. 7.1 is Front LCR, side LR, rear LR, and sub.

I had a theater consultant come out to my house and said in the 7.1 setup, he suggests putting two speakers in the center (maybe 12 inches apart) since the rear is mono....is that true?

I'm not entirely certain. I have heard something similar, but I'd move them a bit farther apart. If you're going to put them that close together, you might as well be using 6.1. This also may not apply in all surround modes. (eg Logic7 I'm sure uses discreet signals to the rears).

Yes, any movie in Dolby Digital EX and DTS ES, as Ken said will be 6.1, so that 6th channel will be in mono. Your receiver, after you tell it that you have a 7.1 setup, will send that same mono signal to BOTH rear surround speakers. But, like Ken, I would put the rear surrounds farther apart than 12 inches.

Here's what Dolby recommends. Click on the "Dolby Digital EX" just below the diagram to see the 7.1 setup.

Notice that the 2 rear surrounds are labeled "mono." Also notice that the distance between the rear surrounds is based on being roughly 135 degrees to 150 degrees from the 0 degree line. So the closer your seating area is to the back wall, the closer together the speakers would be, ACCORDING TO DOLBY. In the real world, you might have to compromise their location a bit. Don't worry about it.

What do you think about putting those rear mono speakers as far apart as the front R&L speakers?

VegasVec,

Just to clarify things a bit: 7.1 channels is not a "standard" mixing format for movie soundtracks. 99% of movies are mixed for 5.1 channels, in studios and mixing theaters with the surrounds on the side walls. That is how the director and the sound mixer hear the playback as they adjust levels in the final mix, and that's ideally the goal of home theater soundtrack reproduction--to mimic what you'd hear in a Dolby Digital theater. Dolby Digital 5.1 is also the standard format for High Definition TV.

Logic7, the music and movie format exclusive to H/K and Lexicon does decode 7.1 channels if you connect the additional surrounds, as does Dolby ProLogic IIx, the newest version of Dolby Pro LogicII, even if you feed it a 2-channel source.

A few movies are mixed in 6.1 channels and depending on the room size and installation, you may hear marginal improvements with a 7.1-channel install. In large rooms, the additional surround channels deliver better overall coverage for viewers throughout the room.

Regards,

Gary, as Alan and others have pointed out, there is no such thing as a 7.1 format. A few movies have a 6th mono channel added(i.e. DD-EX, DTS-ES)and processing such as DPLIIx can steer surround material from either 2 channel or 5 channel sources into a type of stereo for the 6th and 7th back surrounds.

The back surrounds shouldn't be closely spaced, despite what the installer said. This would especially be the case if DPLIIx was being applied for a stereo effect, but the separation should be wider even for the little bit of mono rear surround available from 6.1 sources. This is to avoid a psychoacoustical effect which sometimes can occur with a single centered rear surround in which sounds intended to come from behind "reverse" and appear to be coming from the front. The rear surrounds don't necessarily have to be separated the same amount as the front speakers, but a similar rule could be applied(as Jack's link implies), i.e. separate them about the same distance as your distance from in this case the back wall(hopefully you won't be right up against it).

As Ken mentioned, although no rear center is necessary, you'll of course be using a front center. Since this will be a front projection setup, I'd suggest that you consider using an M22 or even taller speaker vertically oriented on the floor underneath the screen rather than any horizontal center speaker. If there's adequate room beneath the screen a center speaker identical to the left and right fronts would be ideal.

ok, so let me clarify -

I should be ok with front R&L towers, a front center (consider a tower vs vertical speaker), side R&L, and 2 REAR speakers...

The rear speakers should have some sort of reasonable distance between them, almost as wide as the front R&L...

Is that what I gather?

Now I know that very few movies are in 7.1 or even 6.1...so down the road, how will the above mentioned setup be effected? Does this setup allow for some "expansion?"

Also, how does it hook up behind a receiver like the denon? What speaker outs do they have?

You got it. It's hard to say what the future will bring in terms of formats, but I just don't see moviemakers being able to push the amount-of-speakers envelope much farther, just for consumer reasons. Sure, there are those among us who will do anything and have any amount of speakers, but the market's just not there for a greater than (realistically speaking) 6.1 or 7.1 speaker setup. I could be incredibly wrong, though.

Most modern recievers in the market you're looking at will have speaker outs directly corresponding to what we've been talking about.