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7.1-channel speaker placement

 
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The Seventh Taylor



Joined: 17 Aug 2007
Posts: 401

PostPosted: Sun Sep 12, 2010 9:33 am    Post subject: 7.1-channel speaker placement Reply with quote

No, personally I'm not there yet but I came across this article http://svconline.com/loudspeakers/features/7-1_placement_acoustics_812/ and it got me thinking: since there's no single normative loudspeaker configuration for 7.1 like with 5.1 but many options instead, which to choose?

The article suggests according to Dolby it's quite straighforward while DTS offers many alternatives but it bypasses the Dolby Pro Logic IIz set-up as well as some of the DTS variants, one of which (pictured below) matches DPL IIz.



I think whenever I'm ready to add the extra speakers, the configuration with the two height channels is the one I'll go with. A) Because I've head a Dolby DPL IIz demo at the IFA which sounded subtle but interesting and B) because I believe it's much more of an enrichment to go from a 2-dimensional sound field to a 3-dimensional one than to add yet more definition to an already pretty well-defined 2D soundscape.

The second-best option in my view then is the single center height channel, because it's a 3D extension to a 6.1-channel Dolby Digital EX/DTS-ES-compatible set-up.

On a side note, SACD is not 7.1-channel but rather than just 5.1-channel it is technically a 6-channel sound carrier with six discrete channels, with all channels providing full bandwidth. Oddly, the current standard contains no audio descriptor or other metadata that tells how to use the sixth channel. Of course, most multichannel SACDs are 5.0 or 5.1, using the sixth channel for LFE but I've got one title, Sacred Feast, that uses it as a height channel, requiring a ceiling-mounted speaker for proper reproduction. It's a recording of a choir in a cathedral and I've never heard it in 6.0 myself but friends of mine who have were blown away. I guess the Dolby and DTS height-channel configurations are quite compatible with such a ceiling channel lay-out.
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Jens



Joined: 11 Nov 2007
Posts: 99

PostPosted: Sun Sep 12, 2010 12:06 pm    Post subject: Reply with quote

Compatible in terms of speaker lay-out yes but if you want to use both the height channel and the subwoofer, alternatingly, you've got seven or eight speakers to feed with six outputs so you'll still have to do switching, since the receiver cannot do it for you (lacking the information).

Which makes me think: How does Blu-ray Disc do this? Does it have some bits telling what sort of 7.1-channel sound is contained in an audio stream? Or perhaps I should ask whether Dolby Digital Plus, Dolby TrueHD and DTS-HD Master Audio do so?

I want my future 7.1-channel set-up to suit what's on the discs but what conventions is Hollywood going to follow? I guess what they use in the cinemas but is that completely standardised or can each cinema choose its flavour (from Dolby, DTS and SDDS)? I'd assume they go with the two surround plus two rear surround channels. Can anyone confirm?
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Brandon B



Joined: 14 Oct 2007
Posts: 392

PostPosted: Tue Sep 14, 2010 1:22 am    Post subject: Reply with quote

Jens wrote:
Compatible in terms of speaker lay-out yes but if you want to use both the height channel and the subwoofer, alternatingly, you've got seven or eight speakers to feed with six outputs so you'll still have to do switching, since the receiver cannot do it for you (lacking the information).


My friend got a new Onkyo surround receiver. It has 7 built in amplifiers, but 11 sets of binding post speaker outputs.

In other words, the switching is automated. It determines from the DTS flags which speakers the sound should be sent to and switches the amps' output to the correct channels.

Obviously at this late date, we'll never see equivalent functionality added to the SACD spec, but it's interesting that it exists in a mid priced receiver (I think it was about $500-600).

I actually have that SACD and did not know that.
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Yuri



Joined: 28 Aug 2007
Posts: 162

PostPosted: Wed Sep 22, 2010 11:33 pm    Post subject: Reply with quote

Jens wrote:
...
I want my future 7.1-channel set-up to suit what's on the discs but what conventions is Hollywood going to follow? I guess what they use in the cinemas but is that completely standardised or can each cinema choose its flavour (from Dolby, DTS and SDDS)? I'd assume they go with the two surround plus two rear surround channels. Can anyone confirm?

That's right. Dolby Surround 7.1 for cinemas/movie theaters uses he following lay-out:
  • Left
  • Right
  • Center
  • Left Surround
  • Right Surround
  • Low-Frequency Effects
  • Back Surround Left
  • Back Surround Right
according to this Dolby white paper


(Picture borrowed from Brown Blog Films)

I just wouldn't use this many speakers at home Wink
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Brandon B



Joined: 14 Oct 2007
Posts: 392

PostPosted: Thu Sep 23, 2010 7:17 pm    Post subject: Reply with quote

You don't have 30 rows of seats in your viewing room?
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Yuri



Joined: 28 Aug 2007
Posts: 162

PostPosted: Wed Oct 06, 2010 8:55 pm    Post subject: Reply with quote

Hehe, not quite yet, although I wouldn't mind having a viewing room with a few rows more than one :)

Here's an 'interactive' speaker set-up guide from Dolby for surround sound up to 7.1:

http://www.dolby.com/consumer/setup/speaker-setup-guide/index.html
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