Surround Sound – The New Formats
We came across an article at Home Theater Magazine about the various 7.1 speaker configurations available today. It got us thinking. Do we take the standard 7.1 configuration: 3 in the front, 2 on the sides, 2 in the back, for granted? If we could put the speakers anywhere we wanted to, where would they go?
5.1 to 7.1
Traditional 5.1 surround sound systems place three speakers in front of the listening position, a left speaker, a center speaker and a right speaker. The additional 2 speakers were meant to add sound around you, and were traditionally placed immediately to your left and right, maybe slightly behind the listening position. The 7.1 speaker configuration added two more rear surrounds, they are meant to be behind you to the left and right.
Hearing is Important
So with 7.1 setups, you have more speakers off to the sides and behind you than you do in front of you. The human ear is very accurate at pinpointing sounds when they’re in front of you, that accuracy diminishes quickly as the sound wraps around behind you. You may be off by a couple degrees in front, but as many as 20 degrees behind.
Couple that with the fact that there is almost no 7.1 content available today. DVDs max out at 5.1, so they’re off the table. According to the website blu-raystats.com, roughly 7% of the available discs include a 7.1 soundtrack, only 162 of almost 2300. So if you can’t really hear it, and there really isn’t anything to hear anyways, how important are those extra 2 channels? That’s exactly what the folks at Dolby and Audyssey would like you to think about.
Dolby Pro Logic IIz
We’ve mentioned Dolby’s new Pro Logic IIz format before. The main takeaway is that it adds height channels to your home theater. To do that they move 2 of your 7.1 speakers from the back to the front, and raise them up above the listening position, pointed down. Obviously it’s easier to run a few more wires in the front than it is to run them all the way to the rear of the room, so that’s one plus right away.
Since there aren’t any movies mixed in IIz, the Pro Logic technology fills those two height speakers with ambient sounds from other channels in the track. Pro Logic can create the IIz effect from a 2 or 5.1 channel source. Eventually it will support a 9.1 configuration, the standard 7.1 plus the two height speakers. The results of the Pro Logic processing are mixed. A reviewer from Home Entertainment Magazine loved the effect, whereas the reviewers at CNET were underwhelmed.
Another entrant in the modified 7.1 arena is Audyssey’s DSX technology. In addition to the height channels, DSX adds additional width channels to the front of the room. A additional speaker is placed on each side of the room, wider than the existing front left and front right speakers. Audyssey believes the extra width is more important than height, so they’d tell you to add those first.
Like Dolby IIz, there isn’t any content encoded to take advantage of the new channels, either width or height, available in DSX so you have to rely on Audyssey processing to fill them with sound. We haven’t reconfigured our setups yet, so we can’t comment on how well it works. In addition to the 7.1 with new width or height setups DSX will support 9.1 to use both, or either in conjunction with a standard 7.1 system, and of course there will be an 11.1 system that has them all. DSX requires a 5.1 source track.
This is a rare dilemma. First off, we can’t really hear that stuff behind us very well, so it makes sense to move the speakers up to the front of the room. Secondly, there really isn’t much content taking advantage of those speakers, so it makes sense to move the speakers up to the front of the room. That said, there’s absolutely nothing encoded in IIz or DSX, so you have to rely on the processing to get anything from those speakers. How well it works is something your ears will have to tell you.
We don’t think content will be coming out anytime soon that supports the new height or width channels. Movie theaters are reluctant to add new speakers and new processing, so the cinema mixes won’t include them. If the cinema mixes don’t include them, odds are the home mixes won’t either. For the short term, it’s really up to you: leave the speakers behind you and enjoy the 7% of movies that use them, or move them to the front and hope the processing works well enough to make a difference.
But in dream land, where would we put the speakers? We’ve always liked the idea of multiple center channel speakers like Sony uses in SDDS. Screens are getting so big these days, it make sense to put dialog on either side. We’d use 2 in the center. The we’d take the 7th speaker, the one we have left over, and finally implement the often whispered about “god” speaker. Mount it right above your head. That really gives you a sense of height and the feeling that things are falling on you or flying over you.
That, of course, won’t happen anytime in the foreseeable future, but that’s how we’d do it.
Posted by The HT Guys, May 13, 2010 11:43 PM
About The HT GuysThe HT Guys, Ara Derderian and Braden Russell, are Engineers who formerly worked for the Advanced Digital Systems Group (ADSG) of Sony Pictures Entertainment. ADSG was the R&D unit of the sound department producing products for movie theaters and movie studios.
Two of the products they worked on include the DCP-1000 and DADR-5000. The DCP is a digital cinema processor used in movie theaters around the world. The DADR-5000 is a disk-based audio dubber used on Hollywood sound stages.
ADSG was awarded a Technical Academy Award by the Academy of Motion Picture Arts and Sciences in 2000 for the development of the DADR-5000. Ara holds three patents for his development work in Digital Cinema and Digital Audio Recording.
Every week they put together a podcast about High Definition TV and Home Theater. Each episode brings news from the A/V world, helpful product reviews and insights and help in demystifying and simplifying HDTV and home theater.