What is 5.1 surround sound?


Old 12-21-07, 05:04 AM
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What is 5.1 surround sound?

I have a Sony home theater system. Unit works fine with DVDs, etc. I noticed when I pop a DVD in the player and it starts, the display will sometimes read Dobly Digital 2.0 and then later when the movie starts, Dobly Digital 3.2.1. Is the latter the same as 5.1? I have a typical arranagement, 5 speakers + subwoofer. Sorry I do not have the model number but it's not a high priced one ($200- $300)
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Old 12-21-07, 12:23 PM
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Good question. I've not seen that designation before, so I did a little googling. The only references I've seen with that numbering system appear to be European abnd appear to be the same as 5.1. It seems like it would be a more accurate way to describe the speaker setup as the standards are changing all the time. There is apparently still quite a debate about what exactly 6.1 and 7.1 means. And lot of home enthusiasts are now using 2 subs, so 5.2 is more common than you would think.

The reason the nubmers change is due to the difference in the audio channels for being played. Apparently the opening menu/trailer, etc are in stereo and the movie switches over DD. Not that big of a deal.

I would guess that 3.2.1 is the same as 5.1. Look for a DVD with a setup included. It should send a signal to each speaker separately and if you see the 3.2.1 and get a signal where and when the setup says it is supposed to be, then you would have your answer.

Good luck,
Old 12-21-07, 07:05 PM
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Dolby Digital 2.0 is a two-channel encoding scheme that results in basic stereo.

Dolby 5.1 has six discrete channels for left, center, right, left rear, right rear, and subwoofer. The "dot-one" is a discrete sub channel, but it is bandwidth-limited to sub frequencies only. 3.2.1 is another term to describe a six channel system with the same speaker layout: Three in front, two in the rear, and one subwoofer.

If you have an older system or VHS tapes, they probably use Dolby ProLogic. In today's terms, ProLogic would be 4.1 or 3.1.1 because the rear speakers are not discrete. Both rear speakers receive the same signal.

Dolby.com has a great knowledge base about its products. This White Paper (pdf) is enlightening.

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