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I’m using an LG OLED55B6 TV with HDMI ARC output to HDMI input of Sonos Amp. The Sonos Amp powers L&R passive front speakers and is also connected to Sonos Sub 3 and 2x Play Ones as rear surround speakers.

Using a Dolby 5.1 source from Apple TV 4K fed to TV via HDMI 1 I can only get ‘PCM Stereo’ shown on S2 App, confirmed by the Play Ones outputting  the same signals as the L&R front.

Sonos CS tell me that with passives connected as front channel, the Sonos Amp will only operate in 2.1 mode. Before returning the kit to Sonos, has anyone managed to get a Sonos Amp working in 5.1 or, more accurately, 4.1 since it has a ‘phantom’ centre front?

Any advice or comments would be much appreciated! All the research I did prior to purchase indicated that 5.1 was possible with this configuration.

Many thanks,

Melchet.

Sonos CS is wrong - my amp powering front speakers works just fine with DD5.1 together with Play:1 rears and Sub gen2. The whole phantom channel in a strictly speaker 4.1 set-up is based on using Amp as front speakers. I don’t have AppleTv, so your issues might have to do with that.

Under the Apple TV’s audio settings, be sure that Change Format is set to On and the Audio Format is set to Dolby Digital.

What are your TV’s audio settings set to? What specific content are you testing?

Thanks very much for assistance. The lack of 5.1 turned out to be due to two faulty HDMI cables. Both resulted in perfectly good PCM Stereo 2.1 but finally got 5.1 with the Sonos supplied HDMI cable! Is there anything special in the Sonos HDMI cable ie. extra pins used which are NC on other HDMI cables?

There are different specs for different versions of HDMI, not all HDMI cables are compatible with the later versions that include HDMI ARC. I’d suggest reading https://en.wikipedia.org/wiki/HDMI and looking at the cables you needed to swap out. Unfortunately, not all cables are well labeled as to what version of HDMI they were made for, so it may not be as helpful as you’d like, but it’s worth a shot. 

Taken from a Staff post on the forum here…

Any HDMI cable with HEAC support can handle Arc/eARC. Both the HDMI cable which comes with Beam and Arc have HEAC support.

Technically there are four kinds of cable :

  • Regular HDMI
  • High-Speed HDMI
  • High-Speed HDMI with ethernet 
  • Ultra-High-Speed

The cable that comes with the Beam/Arc is a High Speed one with ethernet, whereby the ethernet pins are used for Arc/eArc. Sometimes referred to as HDMI 1.4+

HEAC - HDMI Ethernet and Audio Return Channel

Many thanks for clarification on HDMI cable variants. I used to think an HDMI cable was an HDMI cable, but nothing seems to be straightforward these days!

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