If you have HDMI-ARC and not eARC, you will get DD+ with Atmos, which is what the Fire TV 4K Stick and Roku 4K Ultra use.  Ditto most streaming apps on the TV.  Nobody really knows what the deal is with Apple TV, but it appears it requires eARC to get Atmos.  I’m sure we will find out more when the reviews come out and/or the Arc ships.

so it sounds like it will be great but not prestine.  Is that a fair assessment?  Like I said I want REALLY good surround sound - I’m not looking for perfection

That would be correct.  DD+ is still great, and if you are streaming and not playing 4K Blue-Ray, it’s the best you can get. The fact is, there are very few eARC sets on the market, so you aren’t alone.  

Not sure you’d ever get pristine with a sound bar, you’d probably need to invest a lot more money into a true home theater solution. My suspicion is that with the Sonos Arc, you’ll be hard pressed to tell the difference in sound between HDMI ARC and eARC. 

Thank you all for the input.  Im going for it.  Sonos has yet to let me down...LG on the other hand...

LG doesn’t update old models. You need to buy a CX

I can confirm using Apple TV, I get Atmos out HDMI-ARC from the C8. This is working for me right now:

• ATV 4K > C8 HDMI-1 > C8 HDMI-ARC > Vizio SB3512-F6 (HDMI-ARC)

So, there's no reason to think this would not work with Sonos Arc? Desperately want to dump my Vizio for a number of reasons (but not due to sound quality). The single HDMI port on the Sonos Arc seems an inexplicable design mistake.

Because it’s not an HDMI port, it’s an HDMI ARC port? How many TVs would you want to connect to a single Arc?

It’s not about # of TVs; it’s compatibility with existing devices. At this price point, it should have pass-through, as does my crappy Vizio. The lack of HDMI-In seems to greatly limit the audience for the Arc.

Ah, then you want it to be an HDMI pass through device, and not be an HDMI ARC device. I understand.

How many HDMI input ports should it have? Just one output port? Does that mean the Arc and Sonos software would need to support a selection method for which HDMI port is in use? How does your Vizio handle this? 

I’m no expert, but based on some Reddit threads and Apple’s support info, the *usual* way many 5.1 soundbars have been working is to connect the Streaming Box (ATV or Roku or whatever) to an HDMI In port on the sound bar. Then, connect an “HDMI-OUT/ARC” port to the HDMI-ARC port on the TV. This how all streaming boxes (including the Vizio bar I have) have had to do this because previously there was no such thing as eARC.

Thus Sonos’s design approach isn’t going to work for most people, without buying a new TV. Sonos doesn’t sell TV’s. so it’s not like they’re trying to up-sell new equipment... They’ve just locked out everyone who doesn’t have an Atmos-capable TV (only available from 2018). I can’t really understand their approach.

While I absolutely love pretty much everything I’ve read about the Arc and it looks to be almost exactly the soundbar solution i’ve been looking for for a while, I agree wholeheartedly with this even though Sonos obviously doesn’t. TVs aren’t disposable commodities for most people, even those of us lucky enough to have disposable income to spend on expensive toys like 4K TVs.

I just bought my new TV (a 4K Visio E70-F3 w/Dolby Vision and HDR10) late last year. I didn’t know or care that it was a 2018 model and even though I agonized over the features (OLED vs. LCD? Is Dolby Vision worth it or is HDR10 good enough? Number of local dimming zones? VA vs IPS panel type? etc.) and I’m a technology enthusiast (much to my wife’s and bank account’s chagrin) I had absolutely no idea that “eARC” was a thing coming down the pike that I should even be considering. Hell, after doing a little research I found out that not a single Vizio TV from either 2018 OR 2019 supports HDMI 2.1 / eARC (can’t tell about the 2020 models and they’re not even out yet anyway).  

And since this TV was a replacement for a glorious old Sony KDS-60A3000 that I absolutely loved and had for over 10 years before the light engine went kaput, my wife would be rapidly dialing divorce lawyers if I told her I wanted to ditch our beautiful new TV and buy a new one just because of a soundbar. 

I certainly understand Sonos’ stance - they want ultimate simplicity and they’re building for the future. Unfortunately, right now, “ultimate simplicity” and “bleeding edge technology” aren’t exactly compatible with each other. 99.9% of consumers aren’t going to understand literally any of what will be required at the moment to make this work correctly. And maybe they won’t care. Probably they won’t care. But the people for whom this IS appealing and are willing to spend the $$$ to make it happen do care - a lot. And having just one extra HDMI port to act as a passthrough would fix just about every issue that this type of customer (myself included) is worried about. 

But I’m not Sonos product development and they didn’t ask me. Plus, I’m buying one anyway to see if/how it will work with my system (Apple TV 4K / Vizio E70-F3), so they’re getting my money either way (at least for a little while). 

Guess we’ll all see shortly how it all works out! 

Side rant: I would love for some engineer to explain to me why there isn’t enough bandwidth on the Audio Return Channel for HDMI 2.0(a) to support just about any audio format ever when there IS enough bandwidth for HDMI 2.0(a) to support pushing a 4K image (over 8 millions pixels) with over a billion possible colors per pixel 30 times (or more) per second from one device to another. That limitation blows my mind. 

@Highfalutintodd I endorse your comments completely. At the $700+ price point, a second HDMI port with pass-through seems a necessity, especially on a soundbar that’s interned to be used without an AV Receiver!

I may wait a bit to see how this shakes out. But. if it had another HDMI, I’d be buying the Arc right now instead of complaining here.

Regarding ARC/eARC: I’m no audio engineer, but the problem is probably hardware related. ARC was an ad-on to HDMI, eARC provides not just more bandwidth, but different protocol. (HDMI is so locked-down! Devices verify the capability of the device at other end when establishing a connection.) Similar to the difference between 100Mbps and 1000Mbps ethernet. If your hardware don’t support it, you’re SOL.

Ah-ha. I knew I’d read about this somewhere. This is a good explainer on ARC/eARC and has a table that says eARC requires HDMI cable with Ethernet! Didn’t know that.

https://www.whathifi.com/us/advice/hdmi-arc-and-hdmi-earc-everything-you-need-to-know

Bonus. though I can’t vouch for this info.

https://www.trustedreviews.com/how-to/hdmi-earc-sonos-arc-4035031

@Saguaro7 Those articles are interesting reads to be sure. Not knowing enough about how HDMI functions (hardware vs software) I have to wonder if eARC is legitimately a hardware upgrade or if it could potentially be firmware updatable - e.g. reconfigure the firmware to send these signals using these pins via this protocol. I’m sure some engineer will read this and laugh their head off at my ignorance but it does make me wonder (although all of the other features in HDMI 2.1 make me think maybe it is hardware but what do I know). At the very least it’s probably a chipset change but even then that still makes me wonder if it could be firmware updatable. 
 

Alas, this is all just conjecture and speculation and TV manufacturers aren’t in the habit of adding new features to old TVs because they, of course, want to sell you a new TV. But since I’m not going to be in the market for a new TV for quite some time, a fella can dream

@Saguaro7 If this article (https://hdguru.com/firmware-updates-for-earc-begin-to-arrive/) is to be believed, then yes, eARC IS firmware upgradable…. IF the TV supports HDMI 2.0(b) and IF the manufacturer built it to be upgradeable: 

So what is eARC? It was originally introduced as one of seven core features that will be included in the upcoming HDMI 2.1 standard, but while that standard continues to await chipsets and testing protocols for implementation in commercial products (probably starting to arrive in the second half of 2019), the eARC portion can be added now to some HDMI 2.0b based devices via a firmware update, provided manufacturers have made this part of the equipment design.

Poking around, I see that, of course, my TV’s HDMI port is 2.0(a). 

How any of these standards groups or consumer electronics manufacturers think that consumers should be able to keep track of any of this is beyond me. I know it’s not the same thing, but I can’t help but be reminded of this old xkcd cartoon: 

Pretty sure my 2018 LG C8 is also 2.0(a). <sigh> I think I read elsewhere that no update is going to be available from LG. xkcd: excellent as always.

I have the LG B8 getting atmos/dd+ from my apple tv and on Netflix but Disney+ not working on the inbuilt app or the apple tv.
Big improvement over the playbar IMHO

I also get atmos on tidal so keeping my tv

I currently have the LG C8, Apple TV and a Samsung Soundbar...the LG passes Atmos to the Samsung, so I assume it will pass it to the Arc….my Arc was shipped on Wednesday!

Yes it should though it is dd+ atmos not true HD atmos but it still blows me away!
Even 5.1 is improved IMHO 
Hope you enjoy it

Does anyone have any experience of any non-Sonos soundbar connected to LG Oled and Sky Q combo? Am interested to know if the pass through audio direct to the soundbar and then into the tv fixes the sync issues from the sky box. I have now had a Beam and an Arc and both have the same sync problem 

TIA

I second this. I get dd+ atmos with Apple TV 4k → LG C8 → Sonos ARC.

What are your settings? I can’t get it to work with Amazon Prime or ATV+. But it works with Sky Q and “Das Boot” in UHD.

Do I need a Apple TV 4k for this? I only have a Apple TV 4. gen.

Yes. Only the Apple TV 4K can output Dolby Digital Plus or Dolby TrueHD.

Are you saying that only in relation to the Apple TV 4th gen vs Apple TV 4k? My Nvidia Shield Pro specs indicate DD+ and Atmos support. That said I have it setup with my LG C8 and Sonos Beam right now (plus sonos sub and play:1’s in the rear) so I can’t yet say I have 1st hand experience with knowing whether I would get Atmos sound on the Sonos Arc until I buy one.. I am definitely tempted to try it but damn, the Arc is double the price of the Beam so a bit hard to justify :/ 

Hi! I am getting the Arc as soon as they can deliver it here in Sweden. I am partly getting it because I can not get audio to sync on my Playbar. Sound is behind picture even at minimum delay. How is that working for you on a C8 and Arc? Thanks, Johan