Looking to spec out an Atmos system...

[ScottyD]

Hey guys,

I'm in the research phase of a possible project to convert an existing Pro Tools mixing room to have the capability to mix for Atmos. The mixing room is used for mixing 5.1 and Stereo for broadcast. Possible Atmos content would be used for broadcast delivery.

This is what the room looks like at this current point in time:
Pro Tools HD 12.8.2 with HDX card and 2 HD I/O, Sync HD. Monitoring = XMON > BSS BLU 100 > Crown DCi 8|300 > JBL LSR705i. Also have an Avid S6 as our mixing surface.

We have one HD MADI box not installed, which can be used if need be.

Assumptions:

So with the equipment mentioned, I'm assuming we'd definitely need to add more gear with regard to processing, amplification, and extra speakers. What is the minimum requirement for speaker output in an Atmos room? I'd think either 9.1 or 11.1. So that means our BLU100 would have to have at least another output card with 4 more channels. Have 2 spare ch already - or another unit that can handle 10-12 I/O. Plus a 2nd amp and 4-6 more speakers of course. Then there is the RMU and associated software.

Below are some additional questions and concerns:

Is there any special integration with the S6? Any modules that aid in the mixing process with Atmos?

From looking at the "Authoring for Dolby Atmos Cinema Sound Manual" it looks like we'd need a 2nd MADI box. Is this the case?

Are we better off removing the XMON and HD I/Os and not using the HD MADI boxes and replacing with suitable MTRX? It looks like the stock MTRX has some MADI capability.

My only other concern would be the size of the room. Doesn't this have to meet a certain spec for Dolby to sign off on this?

Am I missing anything else?

Thanks,
Scotty D

[BScout]

Your whole plan has to be signed off by Dolby (not just the room size but the layout, speakers, everything)

You said for "Broadcast" so I'm taking you mean Dolby ATMOS Home. Minimum is 7.1.2. Most ATMOS Home mix setups (on the smallest scale) are 7.1.4 (last number is the overheads.) How many speakers you need is dependant on the room (size). It isn't a case of more = better.

You need a lot more channels to run an RMU. Your HDX system will need 128 channels (MADI) minimum just for that.

Yes, the MTRX has built in MADI and can be expanded with more MADI. The MTRX is addressable by Pro Tools by only 64 channels in and 64 channels out due to having only 2 HDX ports. It can handle a lot more channels internally (and a lot more MADI expansion) --- that will make more sense when you consider routing possibilities even when it isn't addressable by Pro Tools directly.

I suggest you talk with Dolby. You will have to anyway. Also, deal with a dealer who has sold/configured ATMOS setups to avoid making mistakes.

I don't even think the 705i would qualify for speakers for an ATMOS mix. Definitely not for the screen channels.

[mgoorevich]

I had this topic discussed and answered by pros very well a year ago on the GS forum:
https://www.gearslutz.com/board/post...ing-stage.html

[ScottyD]

Good things to note. I will have to reach out to Dolby to see if our current room meets minimum required specs before really moving forward.

In terms of I/O it looks like a 2nd HDX would be needed to deal with 128 channels of MADI. Does this mean a 2nd MTRX is needed as well since each one is capable of 64 ch MADI at a time?

***If going with a second HD MADI then all that is needed is a 2nd HDX (for both boxes) and I'd be able to maintain the rest of the system as it exists today.

I guess Dolby would have to answer if the LRS705is are suitable or not.

Will take a look at that gearslutz thread for more info.

Thanks,
Scotty

[Frank Kruse]

For Atmos Home Dolby wants you to have speakers that are capable of playing back 99dBSPL of headroom without distorting (at listening position obviously). So 79dB plus the 20dB of headroom.

The 705P can do 101dB continuous at 1m and 107dB peak so depending on your listening distance these could be underpowered to meet the minimum specs.

(6dB loss per distance doubling). So 2 m away you are already at the borderline of meeting their specs with the speaker at the edge of going into clipping. But the 6dB is in the free field. In an actual room it's less. But I'd say the 705 might work in a very small room.


Get in touch with Dolby, they will help you spec things out.

[lucienpalmer]

Originally Posted by ScottyD

In terms of I/O it looks like a 2nd HDX would be needed to deal with 128 channels of MADI. Does this mean a 2nd MTRX is needed as well since each one is capable of 64 ch MADI at a time?

***If going with a second HD MADI then all that is needed is a 2nd HDX (for both boxes) and I'd be able to maintain the rest of the system as it exists today.

The MADI outputs don't matter unless you are buying a hardware renderer for the room as well. For smaller rooms, you can use the production suite (was local renderer) to monitor in Atmos. That runs native in the background of PT. Then you only need the number of outputs required to go to your speakers. But then you take the project somewhere else to do the rendering. You might want to do that anyway so you can check your mix, because the 705's are a little too small for surrounds. (ceiling only, maybe)

If you are planning to buy a hardware renderer (only for home theater and streaming Atmos), you will need at least HDX2. I went with a MTRX and Avid MADI to get 64 ch each. And then you still have monitoring capabilities for your S6 via the MTRX.

BTW, the hardware renderer runs about $10k, so budget for that:
https://westlakepro.com/product/dolb...ng-suite-full/