Optical Audio with 5.1 = 3.1 Sound?

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Level 3

521 points

Optical Audio with 5.1 = 3.1 Sound?

I recently bought a Mac Mini... I have a Cambridge Soundworks DTT2500 Digital 5.1 surround sound speaker system and wanted to hook it up to my Mini via optical (I bought the Belkin PureAV cable). I hooked it up at first via the analog and had to use a splitter (the DTT2500 has a line for front and a line for rear... so you can use a Y splitter and it just pumps the sound out of all 5 speakers, but I don't think it will properly channel each speaker). With the optical, however, ONLY the front 3 speakers and sub put out sound (and I cannot use the keyboard to increase/decrease the volume... and the mute button shows the mute sound on my display, but does not mute my audio).

I assume this is NOT normal?

-Keith

Mac Mini 1.66 GHz Intel Core Duo, 1 GB RAM, 100 GB HDD, Mac OS X (10.4.6)

Posted on Apr 10, 2006 5:31 PM

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Answer 1

Apr 10, 2006 6:56 PM in response to Keithos

Are you playing a DVD with Dolby Digital audio? (It doesn't seem that your system supports DTS audio.) If so, in the DVD Player application preferences, have you enabled the digital audio option for your speakers? To get surround sound out of your Mac, you'll have to be playing a DVD with surround sound audio.

Your MP3s probably aren't surround sound files, so they won't play on all the speakers from iTunes.

-Doug

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Answer 2

Keithos Author

Level 3

521 points

Apr 10, 2006 7:34 PM in response to Douglas McLaughlin

Doug,

Interesting... I will try the DVD option and get back to you... I guess all 5 speakers "work" via analog because the system doesn't know how to "split" the signal, but with audio it does know how to split the signal and thus is only pushing audio through the front 3 speakers?

-Keith

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Answer 3

Keithos Author

Level 3

521 points

Apr 10, 2006 8:15 PM in response to Douglas McLaughlin

Doug,

I tried the DVD... I put in "Coldplay Live 2003" and changed my DVD preferences under the "Disc Setup" tab (Audio Section). I changed the selection from "System Sound Output" to "Audio Output - Digital Output - Built - In Output". I then was able to hear sound out of all 5 speakers. 🙂

So I guess MP3/AAC files are not configured to use all 5 speakers?

Thanks,
Keith

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Answer 4

Keithos Author

Level 3

521 points

Apr 10, 2006 8:17 PM in response to Keithos

One other question now that I think about it...

Why is it, however, that my Audio Increase/Decrease/Mute keyboard buttons do not work via Optical? The Increase/Decrease do not even show up on my screen, whereas when I hit the Mute button it at least appears on the screen (although it still does not mute anything)...?

-Keith

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Answer 5

Apr 10, 2006 8:37 PM in response to Keithos

So I guess MP3/AAC files are not configured to use all 5 speakers?

Yes, this is the case. They are probably just stereo files (two audio channels). It depends on your receiver/speakers just how a stereo file plays through, there may be a setting to make stereo files come through all the speakers anyway. But, the audio coming out of your Mac is just going to be stereo with those kinds of files, your audio system may be able to handle the channels differently.

-Doug

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Answer 6

Apr 10, 2006 10:39 PM in response to Keithos

That will happen with any machine sending audio out through optical. Even my Dual G5 does the same thing. The reason being, it's giving a digital, unprocessed feed. It's up to your amplifier to process the audio itself.

Jon

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Answer 7

Keithos Author

Level 3

521 points

Apr 11, 2006 10:37 AM in response to Jon Menegon

Jon,

Thank you.

-Keith

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