Film-Tech Forum ARCHIVE: Upgrading Dolby 5.1 to 7.1

This is topic Upgrading Dolby 5.1 to 7.1 in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Dennis Benjamin (Member # 1137) on 06-05-2014, 07:40 AM:

I want to convert an auditorium from Dolby 5.1 to Dolby 7.1.
We currently use a Dolby CP750 audio processor.
Isn't a matter of adding a few speakers to the back wall?
Then programming the G.D.C. server and Dolby Processor to run a selected feature in 7.1?
Obviously we would have to be sure to ingest the 7.1 version of the feature and have the correct keys.
Then equalizing the sound in the theatre once it is all done.

Are there any other steps I am missing?

Thanks for any input.

Posted by Peter Castle (Member # 1997) on 06-05-2014, 09:16 AM:

I was about to respond simply by saying: all you need is a pair of speakers or sets of speakers and a stereo amplifier, and then adjust the GDC to transmit the 8 channels to the 750. And yes, an EQ is required.

But, as I was unfamiliar with the channel capacity of the Dolby 750, I looked at the specs. Why does Dolby specify that 7.1 cinema sound is Dolby 7.1. Surely it's just 7.1 LPCM. We've just installed a Datasat AP20 to process our sound and it seems to produce 7.1 sound - is it still Dolby's?

Posted by Dennis Benjamin (Member # 1137) on 06-05-2014, 10:38 AM:

I would also mention that the auditorium in question is already tri-amped and it sounds great in 5.1. But I am looking for something a little better than what we have now. Atmos is too expensive.

Posted by Carsten Kurz (Member # 5396) on 06-05-2014, 01:27 PM:

With recent software versions, the CP750 will do 7.1 (+ HI/VI if needed).

What type are your current left and right surrounds?

It's no big deal, after installation of amps and speakers, level/EQ, you will have to add cues to your playlist to select either 5.1 or 7.1. The CP750 will then change between 5.1 and 4_surround encode modes.

Then you tell the distributors/digilabs you have 7.1 capability, so that they supply 7.1 keys to you if available. Typically, 7.1 DCP come as version files to 5.1_OVs, so you will always have a 5.1 version in addition to the 7.1 (if it exists), but you need to ingest both.

We usually receive both 5.1 and 7.1 KDMs, but it took us a while to make all KDM providers aware of the fact that we actually are 7.1 capable. In the beginning, we had to call them often in order to receive 7.1 when we noticed a 7.1 DCP/CPL on the hard drive.

- Carsten

Posted by Dave Macaulay (Member # 813) on 06-05-2014, 04:31 PM:

There are two things - you need to assign DCP channels 11 and 12 (AES pair 6) to CP750 inputs 7 and 8. Odyssey makes cards that do this if the GDC can't swap channels. You need to create a couple of CP750 cues to switch it to 7.1 and back to 5.1 but I don't have these at hand.

Dave

Posted by Daniel Schulz (Member # 1881) on 06-05-2014, 05:45 PM:

quote: Peter Castle
But, as I was unfamiliar with the channel capacity of the Dolby 750, I looked at the specs. Why does Dolby specify that 7.1 cinema sound is Dolby 7.1. Surely it's just 7.1 LPCM. We've just installed a Datasat AP20 to process our sound and it seems to produce 7.1 sound - is it still Dolby's?

It is just 7.1 LPCM on the DCP, no Dolby encoding present and no Dolby hardware required for proper playback.

quote: Dennis Benjamin
I want to convert an auditorium from Dolby 5.1 to Dolby 7.1.
We currently use a Dolby CP750 audio processor.
Isn't a matter of adding a few speakers to the back wall?
Then programming the G.D.C. server and Dolby Processor to run a selected feature in 7.1?
Obviously we would have to be sure to ingest the 7.1 version of the feature and have the correct keys.
Then equalizing the sound in the theatre once it is all done.

Do you already have speakers on the back wall? If so you may not need additional speakers, just a change in wiring and possibly additional amplifiers.