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I have read through some of the topics about this already, but most don’t seem to give a solid answer on projectors that do have HDMI ARC.

 

My plan originally was to get the Sonos Playbar+Sub+Ones with an HDMI switcher (for the optical audio) to go to the Optoma Cinemax P1 UST projector. I just learned about the ARC and it’s Dolby Atmos compatibility. The projector has HDMI ARC and states compatibility with Dolby Atmos. However looking through the forums, I’m not seeing a solid answer on if and how it would work with a projector that does have HDMI ARC (not eARC though). We would most likely only have 2 inputs to the projector anyway, so I don't think we would need an HDMI Switcher anymore. 

 

Can anyone provide some insight into this?

Sorry I’m confused, what exactly is your question?

Can the Sonos arc work with the Optoma Cinemax p1 with the hdmi arc for utilizing Dolby atmos? If so, what’s the proper setup for it to work?

Since the Arc hasn’t shipped, I’m not sure. On the product page, this is somewhat interesting:

Dolby Digital, Dolby Digital Plus and DTS audio passthrough via HDMI ARC or optical S/PDIF.

While technically, ARC isn’t a passthrough, it implies that it will send a Dolby Digital Plus signal can be accepted and converted to HDMI ARC, which could feed the Sonos Arc. In theory. But Dolby Digital Plus and DTS can not be carried by optical, to my knowledge, which suggests the copy writer doesn’t understand what they’re saying. 

Then you’d need to be certain your source device (and streaming company) is capable of sending an Atmos signal over Dolby Digital Plus, so it can be reflected back to the Arc. 
 

Edit: the copy says ‘or’, so maybe I’m being too critical. 

Hi @ajkeith147 

Note: The following is conjecture based upon information published by Sonos and Optoma. A real world test would need to be conducted as proof of statement.

According to the specs published here the Optoma CinemaX-P1 it is capable of Dolby Digital and Dolby Digital Plus passthrough via HDMI ARC or optical S/PDIF.

The Arc if you connect to a TV (and I would assume a Projector) using ARC, the Dolby audio formats supported are dependent on your TV/Projector model and manufacturer. The TV/Projector may be capable of sending Dolby Atmos, Dolby Digital Plus, and Dolby Digital. An ARC connection cannot support TrueHD or MAT.

Therefore, :thinking:based upon the above the Arc should receive and output Dolby Digital and Dolby Digital Plus sourced by the Optoma CinemaX-P1.

Wanted to jump in here and hopefully add a bit to the conversation. I actually have the Optoma CinemaX P1 projector and I got my Sonos Arc + Sub last week. The HDMI 1 port on the projector is an ARC port (not eARC). My setup is AppleTV 4K > (HDMI port 2) CinemaX P1 (HDMI port 1) > Sonos Arc.

The best that I’ve been able to get (by using the S2 app to tell me what the audio is) has been 5.1 surround. I have played Atmos content in iTunes and the S2 app has not indicated that it’s actually getting Atmos. Additionally, there’s a noticeable audio delay in the setup that I have that wasn’t present when using the CinemaX P1’s built in speakers. The audio delay isn’t more than a second but it’s still noticeable. The best I’ve been able to do is adjust the delay settings on the projector to -50 (the ‘highest’ it will go). 

 

All that said, HDFury has announced they are working on a device that will let you bypass the projector (or TV’s) ARC port and go straight to the Sonos Arc. It’s still early development but I’m hoping that it will solve both the missing Atmos and lip sync issues I’m having. You can check out more about that device here: https://www.reddit.com/r/sonos/comments/hb23zl/first_rendering_of_the_adapter_that_will_add_earc/

There’s already a thread about the HDFury device here. 

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