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Shouldn't All New HD Receivers be 8.1 not 7.1?

post #1 of 8
11/15/07 at 12:09pm
Thread Starter 
In terms of available output, to be fully compatible with ALL existing and pre-existing audio formats to work?

I had always thought 6.1 with rear center channel was a good idea. Now with 7.1 it's 3 up front, 2 on the side, 2 in the rear.

So if you or I have any of the 6.1 discs, we're out of luck...no?

Any units out there that offer 8.1, either players or receivers?
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post #2 of 8
11/15/07 at 12:40pm

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

Nah-- The original THX EX spec (which kicked off this 6.1 craze) specified that the single rear channel was to be used to drive two rear surround speakers. Apparently, a single rear speaker could, under certain conditions, collapse the sound field.
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post #3 of 8
11/16/07 at 5:40am
Thread Starter 

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

I don't see how 3 discrete channels could collapse the soundfield. Let's say that from the rear you have a chopper moving front from the right, the sound of boots on the ground from the left heading to the screen and a jet screaming towards the screen from the middle.

I would imagine the placement of sound would be concrete.
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post #4 of 8
11/16/07 at 9:26am

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

Actually the 2 rear speakers in a 7.1 setup are not supposed to be placed in the rear left and right corners as they are in the case of the front left and right speakers. The 2 rear speakers are placed a little towards the inside on the back wall, the missing rear center channel soundfield is created by feeding both the rear speakers withthe same sound as and when needed. Most importantly, 7.1 setups are meant fo larger rooms, for smaller rooms a 6.1 setup is best, wherein you would place 2 speakers to the side and 1 speaker in the center of the back wall.
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post #5 of 8
11/16/07 at 7:53pm

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

The reason why the soundfield would collapse on the THX EX spec is simple: the surround process it is based on is Dolby Digital Surround EX, which has a matrixed rather than a discrete rear centre channel, meaning that if you were to only use one speaker (given the fact that a centre rear channel would carry less distinctive sound than the front centre in a typical Dolby Stereo matrix [read: sound effects rather than dialogue]), that matrixed sound could potentially be drowned out by the surrounds, since they would still be carrying a portion of the matrixed rear centre channel. This is reduced by feeding the monaural signal to two speakers, giving the signal twice the power. It should be less of an issue with discrete 6.1 tracks, but someone still decided that 7.1, with left and right rear surrounds (in addition to the side mounted surrounds) would be a good idea. Whatever.

FWIW, 8.1 would be overkill. For comparison's sake, the SDDS 8 channel spec for theatres is left, left centre, centre, right centre, right, right surround, left surround, and subwoofer, and will never see the light of day outside of theatres for good reason: a home theatre would have to be FRICKIN' HUGE to take advantage of it.
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post #6 of 8
11/16/07 at 9:31pm

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

The Sunfire Theatre Grand 5 supports a 9.1 configuration with side axis speakers. At a certain point pre-pros become user/installer programmable, so I wouldn't be surprised if left centre and right centre channels were in use in someone's "home" theatre.


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post #7 of 8
12/12/07 at 12:14am

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

Quote:
Originally Posted by JeremyErwin
Nah-- The original THX EX spec (which kicked off this 6.1 craze) specified that the single rear channel was to used to drive two rear surround speakers. Apparently, a single rear speaker could, under certain conditions, collapse the sound field.
My understanding was that due to the way the ear perceives sound, a single rear speaker directly behind the listener could sound like it was actually directly in front, hence the preference for two speakers behind, both off-centre, playing the same channel to create a phantom centre directly behind the listener.
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post #8 of 8
12/12/07 at 3:59pm

Re: Shouldn't All New HD Receivers be 8.1 not 7.1?

Quote:
Originally Posted by Yee-Ming
My understanding was that due to the way the ear perceives sound, a single rear speaker directly behind the listener could sound like it was actually directly in front, hence the preference for two speakers behind, both off-centre, playing the same channel to create a phantom centre directly behind the listener.

I could see where it might be possible, however I have yet to hear a system that actually did that. Not once did I ever feel like the sound was coming from the front in my previous 6.1 setup. If it does, I would suspect a setup issue including speaker placement, distance and level adjustments.

For 6.1 sound, you don't need 8.1 inputs...or I don't understand the question? For 6.1 channels of audio you need 7 inputs - 1 sub, 6 main channels; 7 channels + sub for 7.1, which is what the typical receiver has these days. What would the additional channels be needed for?
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