Please define “full” and “limited”? 

Well I am not competent enough on the subject to give you precise audiophile definitions … of course none is none and that would mean I just stay with the Playbar and forgo the upgrade to the Arc (not replacing an 18 month old high end expensive TV at this point) … but “limited” relates to more expert insights by some on this site (and elsewhere) who have said that you can use the Arc with ARC capability even if you don't have eARC but that would mean you will get less than the fulsome quality and features that you would get with eARC capability … that help clarify? Thanks.

Sorry I meant to add that “full” means the full Dolby Atmos immersive surround sound, voice sync, all speaker utilization.

Further notes: right now I see that my Samsung Q9 TV is set to “PCM” … and in Expert Settings Dolby Digital and Dolby Digital Plus are greyed out in the current setting and connections (optical right now not ARC).

Although it varies per TV to what extent Atmos is passed, the most you can get with ARC is Dolby Digital Plus with Atmos.  DD+ is an enhancement over standard DD, but it is still lossy.  To get TrueHD with Atmos, which is lossless, you need eARC.  Note, most streaming services use DD+, there are not many sources of TrueHD outside of Blue-ray.

So, you could define, if you so choose, the two kinds of Dolby Atmos based on the bandwidth required to carry the data. “Limited”, to use your term, is carried on Dolby Digital Plus connections, which require HDMI ARC or higher bandwidth connections. It can not be carried on optical connections.

“Full” requires the use of Dolby TrueHD, which is carried on eARC. This will carry all available speaker channels to a full Dolby Atmos system.

Caveat here, I don’t have an Arc yet, but I’d be stunned if you could hear the difference between the two kinds of connections types when using a Sonos Arc. It’s a sound bar. There are built in limitations about numbers of speakers and speaker placement. I suspect that Dolby Digital Plus, via HDMI ARC will be quite satisfactory for using the Sonos Arc. However, if you have a 20 speaker + sound system set up with all the required speakers in the correct locations/orientations, I suspect that you could hear a difference in the sound between the two formats. 

So, with that information imparted, I’ll suggest these answers to your questions:

1. Limited, as defined by the connection type, assuming your TV can pass Dolby Digital Plus via HDMI ARC. 
2. No one is sure yet. There’s discussion around that Apple uses the the MAT format, which is only carried by eARC, but there are some TVs that might be able to translate that to HDMI ARC. Until you have an Arc and can test, there’s no real great way I’ve seen to figure this out. Looking a rtings.com is probably the best at this point, but I’m not convinced that I’m comfortable with the accuracy, having not done any of this testing myself. They could be 100% right, and I lean that way, but I just am unwilling to put money on it. 
3. Not currently. As has been discussed in many, many threads, everyone is looking for a device that splits off an eARC signal from an HDMI input and sends that out. No one has found one yet. 

Thank you. As a laymen in these matter I take what you are saying to be encouraging. I don’t use Blue-ray any more -- our family streams via AppleTV+, Netflix, Disney+, and Amazon Prime Video.

So if I understand what you are saying does this mean if I switch the connections from the optical hook up to the ARC one and attach that to the new Arc bar when it arrives I should be able to get the full benefits DD+ with Atmos with those streaming sources. That make sense?

Yes, except for maybe Apple TV. That remains to be seen. I’m anxious to get my own Arc, and see how the Vizio handles the MAT signal from the Apple TV to the HDMI ARC port.

I’d like to by a Sonos Arc for my Apple TV 4K.  Apple makes it clear on their site that ATV does not play Atmos via Arc.  So it looks like I won’t be buying a Sonos Arc.  Unless after the Arc is released it magically works with my ATV and plays Dolby Atmos.  Pretty sure that won’t happen.

I basically have the same setup as you (2018 Q9F, Apple TV 4K). From everything that I’ve read, I will not be able to pass an ATMOS signal to the Arc. As you note, the Samsung does not have eARC, so “full” ATMOS was never going to happen - I don’t even have a Blu Ray player so this wasn’t a realistic option for me as I understand streaming services do not carry this. 
 

For “partial” ATMOS, my understanding is that the Apple TV will not pass the signal via DD+ like some of their competitors (Roku, for one). I read it is actually a higher quality version than the lesser implementations within other streamers, but is too big to carry over ARC. So, it is likely that this setup will not give “partial” ATMOS either (Apple recommends connecting directly to soundbar, which obviously the Sonos ARC is not capable of). This is of course all speculation until someone can actually test it. 

I will be interested to see confirmation of the above, and similarly if getting the benefit of Dolby Digital+ alone is worth upgrading from my Playbase. Also curious to hear feedback in music / separation. I’m happy with the Playbase in my condo, but could always be happier. 
 

Yes the lack of robust interoperability with the ATV might be a deal breaker for me too. Not sure the ROI will be there unless something changes. Of course a new ATV is rumored to be released in 2020 so who knows what that will offer. 
 

finally anyone know anything about a rumored Samsung firmware update enabling eARC on recent ARC TVs? Probably asking too much but I’ve got a lot invested in this fairly new tv model.

I’ve not seen any rumors. And since it would require new electronics, it’s hard to believe it could be a software update. 

I have a 2018 Samsung Q9F, an Apple TV 4K, and an Arc. I get same issues as noted above, that the Samsung will output only PCM to the Arc and the option to select Dolby 5.1 or Plus is greyed out. Changing the audio output settings on the Apple TV 4K seem to have no effect on this. I did read  that Samsung seems to be updating the software on some older TVs so that the HDMI ARC port works like eARC where the underlying hardware is capable of supporting that. I don’t know whether this will happen for the 2018 models or not. In the meantime, I’m considering trying something like this (https://www.amazon.com/HDMI-Splitter-1x2-4K-60Hz/dp/B07VP37KMB/ref=pd_sbs_23_5/130-9843274-2515207) to split the signal coming out of the Apple TV 4K so that the Arc gets ATMOS and the TV gets Dolby Vision. I should add that I haven’t tried the optical to HMDI out from the Samsung TV to the Arc.

The AppleTV uses LPMC to pass high definition audio. At a guess Your TV would probably down mix it to PCM Stereo worst case. There are similar reported issues on other TVs. LG have released new firmware that enables LPCM pass through on the C9 via eARC. Once the Sonos Arc gets updated for LPMC in the future than at least on those TVs the problem will resolved  

Potentially your TV might be able to pass DD + from the internal Apps. You would probably be best to contact Samsung directly to understand the pass through capability of your TV. 
 

Splitting the hdmi audio and video and trying to feed the audio into the Arc will not work. The Arc is expecting an ARC/eARC input and this uses different audio pins compared to the standard HDMI audio. 

Hopefully Sonos will prioritize the LPCM update.

I have the same setup as you.  Sadly, I’m not confident that we will ever be able to have ATMOS, or even DD+, from external devices (such as the ATV 4K) as it seems passthrough will not work.  I’ve seen some reports that Netflix on the internal app may pass ATMOS.  But my family is very comfortable with the ATV interface and that is what we primarily use for content, so don’t think it’s worth it for me to switch to another streaming solution just to get ATMOS on one service.

I’ve held off on pulling the trigger for the Arc until I saw some test cases with my setup, and looks like I made the right call for now.  I’m sure it’s a solid step up from my current Playbase/Sub combo, but for now think I will stay put.  But fingers crossed for a software update that will magically enable passthrough!

And kicking myself for not getting the LG as I was on the fence...

I installed my new Arc, sub and a pair of one's yesterday. Connected the Arc to my 2019 Samsung Q90r TV with the provided HDMI cable. Have an Apple TV 4k connected to the TV as well with this HDMI cable. https://www.amazon.com/gp/product/B07NXPS94Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I can confirm that I'm not getting any Arc content from Netflix or iTunes Movies via the Apple TV 4k. On the embedded apps on the TV, I am getting Atmos from Netflix. I'm not able to get it from the iTunes Movie app on the TV I think because Atmos isn't supported in the app. Haven't tried Amazon Prime yet.

I've seen the talk of a firmware update potentially bringing eArc to this TV - definitely hoping that occurs. Also talk of a new Apple TV coming soon - perhaps it will handle Atmos differently and that will fix the problem. 

I tried the built-in Netflix app this evening and was able to get DD+ on the Arc. Whether the sound options are greyed out in the TV sound setup or not does seem to depend on what the current stream is presenting. Since my Q9F supports ARC but not eARC, I don’t think I’m getting Atmos even via the TV’s built-in app, just DD or DD+. Once the ARC supports LPCM, I think using a splitter from the Apple TV 4K to the Arc and TV ought to do the trick.

@jam9 I have a similar setup to you and been struggling to get anything other than 5.1. Can I ask what film/program you used on Netflix to get DD+?

Many thanks 

I hope you’re right, but I believe that a splitter will not work because the Arc needs to receive an HDMI ARC input.  I’m not familiar enough with LPCM, would that change this requirement?  I’m not even sure that the Q9F would pass LPCM, at least from extrernal sources.  But, would love for someone to test this once this capability is enabled!

Hi - i have a Samsung Q90R , Sonos ARC and heres my experience with the setup:

Connection is: Arc>TV>Various Devices

Internal Apps: Atmos for Netflix, Amazon Prime. Not detected for Disney+ or Apple TV

Amazon Firestick 4K: Atmos for Amazon Prime, Disney+ (symbol but limited due to Europe restrictions. Not detected for Netflix

BT Youview:  No Atmos for internal apps

PS4 Pro: No Atmos passthrough for any internal apps

No lip sync issues encountered.

I took a look again just now on both Netflix and Amazon, both through the Samsung apps and via Apple TV. I can only see content available in up to 5.1. However, I can confirm that the HDMI ARC connection is at least passing this through in all cases. I could swear I was able to find DD+ yesterday but I just don’t see it now, even after having gone through a bunch recent uploads on the two services.

My understanding of HDMI ARC is that it’s just a two-way link and there is no difference in the cabling. Anyhow, I ordered a splitter and will try it out, but I’m guessing that we’ll need Sonos to update the Arc for LPCM first so that it can decode the Atmos signal that the Apple TV 4K actually sends. In the meantime, 5.1 seems to work fine.

In case it helps anyone I’m getting ATMOS through the netflix app on an LG b7 oled, not bad for a 2017 tv!, prime only seems to be did, switching out the hdmi cable with the supplied one did the trick, oh and it sounds absolutely incredible

I also have a Samsung 75” Q9FN, with Sky Q.

My ARC arrived this morning to replace my Playbar. I already have the Sub and Surrounds. 

I already knew the Q9 does not support eARC. The Sonos ARC is connected via HDMI/Arc

Neither the Samsung apps nor Sky Q will output ATMOS in my setup - only DD 5.1

It is disappointing the TV does not support eARC considering I paid a significant sum of money for it, but there ya go - my mistake. I didnt realise I was gonna want eARC further down the road.