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Surround sound formats for Arc

  • 22 July 2020
  • 2 replies
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I’m interested in getting an Arc. I’d also be getting a new TV, and so can make sure it has the right features. Even so, some discussions about surround sound support give me pause. There doesn’t seem to be one definitive explanation for all this, so here’s my best attempt, as someone who hasn’t typically paid much attention to different surround sound formats, and who is new to Sonos products. Please let me know if I’m understanding correctly, and if there’s anything I’ve gotten wrong.

In a traditional HDMI-centered setup, various devices send digital AV signals to a receiver, which decodes the audio to analog for its speakers, and passes on the video to a TV. Each device has its own preferred digital audio output format; the receiver supports most every kind of signal—various Dolby formats, DTS formats, and raw PCM.

The Sonos Arc uses a different model: all digital audio signals come from the TV via its ARC HDMI output. Other devices send their signals to the TV. Three limitations:

  1. ARC supports a limited number of surround sound formats. For the widest range of support, you want a TV with eARC.
  2. Many TVs only send 2.0 audio over ARC, at least when the audio comes from an external device. And even TVs that support some surround formats will, for other formats, convert to 2.0. Ideally an eARC TV would not have this limitation, but different brands behave differently. 
  3. The Sonos Arc only supports surround sound in a Dolby format—Dolby Digital, Dolby Digital Plus, Dolby TrueHD (the latter two are able to carry Atmos metadata to the Arc). It also supports stereo audio as PCM 2.0 (maybe other stereo formats too?). In a coming firmware update, Sonos has promised to add support for PCM 5.1.

What this means for some concrete use cases:

  • Netflix on a native TV app: probably sends audio via Dolby Digital Plus over the ARC cable. Works fine.
  • Over-the-air TV signals processed natively by the TV: audio is encoded as Dolby Digital, works fine.
  • Apple TV 4K, connected via HDMI to the TV: preferred output is Atmos over Dolby Digital Plus (I think—they just call it “Atmos”). ARC should support this, Sonos Arc can handle it. For non-Atmos surround sound, Dolby Digital is the standard and works fine with Sonos Arc.
  • Nintendo Switch, connected via HDMI to the TV: surround sound is PCM 5.1. Requires eARC to pass through (and some eARC TVs still may not support it). Sonos Arc can’t handle it right now, should do so after a firmware update.
  • Blu-ray Player, connected via HDMI to the TV: prefers sending audio in its encoded format from disc, which is often some flavor of DTS. The TV may or may not pass that through, but it doesn’t matter because Sonos Arc can’t play it.
    Most Blu-ray players can be set to output PCM 5.1, which could be played if the TV has eARC, the TV supports PCM 5.1 pass through, and Sonos Arc has gotten its future firmware update. In this setup, you’ll want an easy way switch between Dolby formats for some discs and PCM 5.1 conversion for other discs. (I’m not optimistic. It’s probably buried in a settings menu somewhere.)
    A few Blu-ray players can be set to output/convert to Dolby formats, which eARC can hopefully pass through, and which is the ideal format for Sonos Arc.

Does that cover it? So I should wait for the firmware update, get a TV with eARC that faithfully does passthrough, and maybe get a Blu-ray player that can convert DTS to Dolby Digital?

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2 replies

Annazel S
Userlevel 5
Badge +16

Hi @dansmith21.

Thanks for reaching out and welcome to the community!

I appreciate your interest in getting the Sonos Arc, let me help by providing additional information we need to know about the product.

First off,  this article will describe some basic requirements when using Sonos speakers with your TV.

We need to learn as well the supported audio formats on your home theater speaker.

Then here is the outline of the main factors that determine if your Sonos Arc can play Dolby Atmos audio:

  • HDMI ARC and HDMI eARC

  • Streaming services

  • Source devices

 

Let us know if you have any other questions or concerns, we are always here to help.

Help others find useful content by clicking the like button and selecting the best answer to your question
H
Userlevel 6
Badge +7

A man after my own heart - analytical and obsessive compulsive! :-) 

I think, generally, you’ve got it. It’s a complex subject with a lot of variables and you seem to have wrapped your head around it about as well as anyone. I’ll make a couple of comments, below, if I feel I can add anything (FWIW), but overall solid work. 

Given all of your research, I’m sure you’ve come across Arcana but I’ll mention it here anyway. HD Fury’s Arcana adapter (https://www.hdfury.com/product/4k-arcana-18gbps/) is something that over 700 of us have pre-ordered so far in hopes of being able to bypass many of the issues and complexities surrounding the current state of HDMI-ARC/eARC. There are several topics on this forum discussing it (including a couple started by me), but if you’ve got questions about it will be happy to answer. 

 

  1. ARC supports a limited number of surround sound formats. For the widest range of support, you want a TV with eARC.

 

Generally, yes. Although eARC still seems to be somewhat in its infancy so even some TVs with eARC aren’t foolproof - at least yet (looking at you here, LG). 

 

 

  1. Many TVs only send 2.0 audio over ARC, at least when the audio comes from an external device. And even TVs that support some surround formats will, for other formats, convert to 2.0. Ideally an eARC TV would not have this limitation, but different brands behave differently. 

 

This is very dependent on the make and model of the TV, as you correctly state. Older/early HDMI-ARC TVs seem more limited to 2.0, but on more recent vintage sets I don’t think that’s nearly as much of an issue anymore.  Could absolutely be proven wrong on this point, however. 

 

  1. The Sonos Arc only supports surround sound in a Dolby format—Dolby Digital, Dolby Digital Plus, Dolby TrueHD (the latter two are able to carry Atmos metadata to the Arc). It also supports stereo audio as PCM 2.0 (maybe other stereo formats too?). In a coming firmware update, Sonos has promised to add support for PCM 5.1.

 

Spot on. You can also add Dolby MAT to this list, which is the transport container Apple TV uses. MAT is unique because it can contain just about any sort of audio codec / format. This also includes LPCM 5.1 which currently puts the Arc in the bizarre situation of technically being able to handle multi-channel LPCM…. but only when received in a Dolby MAT container. Super weird (and I’m guessing why Sonos didn’t have a problem quickly announcing that they’d be able to add multi-channel LPCM support to the Arc). 

 

What this means for some concrete use cases:

  • Netflix on a native TV app: probably sends audio via Dolby Digital Plus over the ARC cable. Works fine.

Depends on the TV, but yes. My Vizio E70-F3 falls into this category which lets me get Atmos over DDPlus from the TV’s built-in Netflix app. 

 

  • Over-the-air TV signals processed natively by the TV: audio is encoded as Dolby Digital, works fine.

 

Should, yes. 

 

 

  • Apple TV 4K, connected via HDMI to the TV: preferred output is Atmos over Dolby Digital Plus (I think—they just call it “Atmos”). ARC should support this, Sonos Arc can handle it. For non-Atmos surround sound, Dolby Digital is the standard and works fine with Sonos Arc.

Here’s where things start to get tricky, and it’s thanks to that Dolby MAT container I mentioned earlier. Apple TV can output DDPlus…. but only via that MAT container. The reason it does this is because it allows Apple to also package the Siri and system sounds along with the source audio and it’s precisely what MAT was designed to do. Unfortunately, MAT takes up a lot of bandwidth and more or less seems to require eARC to really work. However, SOME PEOPLE have reported that they’ve been able to get Atmos from their Apple TVs via a non-eARC TV. That is awesome for those people and I am super jealous because my TV does not fall into that category (mine will pass the Dolby Digital Plus signal, but NOT the the Atmos metadata). 

For non-Atmos surround on Apple TV, you should get either Dolby Digital or Dolby Digital Plus. Or, in certain situations, Stereo 2.0 (looking at you here, Hulu on Apple TV - you get that dunce cap back on until you decide to straighten up and fly right!). 

(Side note: Atmos is Atmos, regardless of whether it’s coming over Dolby Digital Plus or Dolby True HD. Dolby Digital Plus is just more compressed in order to take up less bandwidth which is why ALL the streaming services use it for Atmos. TrueHD is “lossless” so theoretically the sound quality is better but it takes up a TON of space so it’s only used on Blu-ray / UHD discs and players. One isn’t more “real” than the other though a lot of people seem to think otherwise.) 

 

 

 

 

  • Blu-ray Player, connected via HDMI to the TV: prefers sending audio in its encoded format from disc, which is often some flavor of DTS. The TV may or may not pass that through, but it doesn’t matter because Sonos Arc can’t play it.

Most BDs have multiple audio tracks on the disc. The player will attempt to send whichever audio track you select. But yes, if that flavor is DTS, the Arc won’t know what to do with it and you won’t get any audio. UNLESS either your Blu-ray player OR your TV can transcode the DTS audio to Dolby Digital (which some can). 

 

  • Most Blu-ray players can be set to output PCM 5.1, which could be played if the TV has eARC, the TV supports PCM 5.1 pass through, and Sonos Arc has gotten its future firmware update. In this setup, you’ll want an easy way switch between Dolby formats for some discs and PCM 5.1 conversion for other discs. (I’m not optimistic. It’s probably buried in a settings menu somewhere.)

The conversion to PCM has to happen somewhere (something’s decoding the audio after all, whether it’s the player, a receiver, a TV, or even the Sonos Arc), so it might as well be the BD player in this case. Which would prevent you from having to “switch” back and forth between Dolby Digital and PCM formats. 

 

 

  • A few Blu-ray players can be set to output/convert to Dolby formats, which eARC can hopefully pass through, and which is the ideal format for Sonos Arc.

 

In this scenario you wouldn’t need eARC for Dolby Digital or Dolby Digital Plus conversions. Plain-jane HDMI-ARC will do Even regular old Optical connections can handle Dolby Digital (but not Plus). 

 

Does that cover it? So I should wait for the firmware update, get a TV with eARC that faithfully does passthrough, and maybe get a Blu-ray player that can convert DTS to Dolby Digital?

TV - If you want to get an Arc and you’re in the market for a new TV, for best future compatibility I’d definitely get one with eARC. If you don’t want to get a new TV, or the TV you really WANT to get doesn’t have eARC, get an Arcana adapter and you’ll be able to bypass the TV’s audio capabilities completely. 

Firmware - Depends on how much you care about getting more than Stereo 2.0 out of your Nintendo Switch. If that’s a dealbreaker, you might want to wait. This is a feature that a lot of people are up in arms about and that I, personally, couldn’t possibly care any less about. So it’s very personal. ;-) 

Blu-ray Player - If BDs are still a thing for you, you’re probably going to want one that can convert DTS to Dolby Digital, yes. As I’ve opined at length in other posts, the Arc seems to be built for a future where eARC TVs are prevalent and physical media is gone. So you’ll have to jump through some hoops in order to keep enjoying your BDs to the fullest with Arc. Unless you want to do like many of us have and rip all of your discs to a Plex server which, while a huge PITA at first, is really awesome when it’s up and running. :-)

 

 

 

Arc + Sub 3 + One SLs = Awesome and Loving It!
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