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