So is HDMI 2 the eARC connection? Have you tried HDMI 1?

 Thanks for the suggestion. Yes, the HDMI 2 slot is the ARC connection, I tried switching to the different HDMI slots just in case but no success sadly

What are your audio sources and how do they connect to your system?  We need a fuller picture (as it were).

I've only got 1 hdmi cable running from the projector to the beam. Nothing else is connected to either of them apart from power and the Android stick of the projector. 

 Here is a picture of the HDMI connected to the projector. Also a picture of the settings, I made sure to turn on audio return on the projector as well. 

OK. What content are you playing from the Android stick?  Is the picture working OK?

Please show settings for audio rather than display.

So far I've been playing off of YouTube and worked fine for the video but never could get any audio out of the sonos.

Couple of comments, which may or may not be helpful. 
 

1. The HDMI cable in your picture doesn’t seem to be the one supplied by Sonos. Which raises the question of what level of HDMI compliance it is. It’s, at least in my mind, a 50/50 chance it isn’t fully HDMI 2.1 compliant, which implies full throughput and speed of data transmission concerns. Double check the type of cable it is. And, whichever cable you’re testing with, try reseating it at both ends to ensure full contact. 
    
2. YouTube doesn’t transmit in a 5.1 compliant stream, only stereo. You’d be better off using a DVD/Blue-ray player attached to HDMI 1. . Or, if those are ‘internal apps’, pick one other than YouTube, for testing purposes. 

Are there any additional HDMI settings beyond “Raw”? What are the EDID choices?

There is something in a deep recess of my mind about having to set up a Beam or Arc on a TV before using it with a projector.

But I can't find anything about that and cannot think why it would be needed, nor when. I may have imagined this - can anyone help?

Maybe you’re thinking about the fact it needs to be set up on an ARC system first? Which most projectors are/were not?

Not sure I’m helping, sorry, John. 

That may well be helpful Bruce. Maybe whatever I have vaguely remembered doesn't apply with a projector that has an HDMI ARC output, which I think is still fairly rare. Or maybe it's needed for CEC, which may not be on a projector.

This could be a complete red herring.

ARC is a subset of CEC, I believe. So if the projector has ARC, it has CEC. And yes, I agree, I think there are very few projectors that have ARC. Took me 10 minutes this morning when I first read the OP to confirm that this device does, and that it’s on HDMI 2. Thank god it was on the first page of the sales data, having to hunt for the website was painful enough. 

But you’re absolutely correct, this might be a red herring. 

Lol. Nevertheless, another BenQ projector, the W2700 has HDMI-ARC output but is not CEC enabled. 

https://www.benq.eu/en-lv/support/downloads-faq/faq/product/application/projector-faq-k-00086.html

And there is a suggestion in this thread that the Beam has to be set up on a CEC enabled device, although that is in the context of using an Arcana device.

Well, hell. Ignore me completely, then :)

Good references. 

But I think this is first thing to check. 

Thank you for all the answers, really appreciate the help!

Sometimes the most simple things are the ones we look over sadly

I could not get myself to believe until late night that the HDMI cable would be the problem. After all, I had all of this installed by a professional company who charged me almost 200 usd for the installation itself how could they make such a silly mistake especially since I specified the speaker Arc setup.

Turns out the cable was at fault….  I moved the speaker below the projector and tried connecting with the cable that is delivered in the box. 10 seconds later, voila, beautiful and crisp sound at last.

Now I guess I will have to run a new 10m HDMI cord in my ceiling…unless there is an adapter I can use with the current cable ? Otherwise could someone point me to an HDMI cable that supports Arc?

To answer some of the  other questions on the thread.

Here are the settings available in the projector (which all work perfect with the Sonos cable)

HDMI EDID: Standard - Enhanced

Audio return: LCPM - Raw - Raw +

I will be using Enhanced and Raw + I guess? not very familiar with what the differences are.

I’d guess there is a manufacturing fault in that cable. Based on those specs printed on it, I’d expect it should have worked….so I wouldn’t blame the installer except for not testing after installation. I was just lucky, just because it didn’t match the look of the Sonos cable. 
 

Don’t overspend on HDMI, they’re digital, but you’d be looking for any HDMI 2.1 (high speed) type cable. I tend to use Belkins, bought from Blue Jeans cable, sometimes direct, some times through Amazon. Don’t get pulled in by the Monster Cable hype ;)

Pin 13 of an HDMI-CEC connection carries the CEC data and this pin is wired in common with all HDMI sockets on each piece of equipment. Essentially there is a ‘network’ running on the CEC pin. It’s a very slow network running at about 480bps. This “common” aspect can cause trouble if there is a rogue device in use. I’m not sure if CEC was part of the original HDMI spec, but I’ve seen discussions about CEC dated in 2004. Some devices are so nasty that the best approach is to disable CEC for that device. If there is no option for this or the option does not work, there are small little adapters that will physically disconnect pin 13. Some TV’s might require this if disabling CEC also disables ARC.

“ARC” is a second audio path to allow a target device, such as a TV, to send audio back to the originating device. This is what allows TV Apps to send audio to the SONOS Arc or an A/V receiver. Since HDMI-ARC audio uses a separate set of pins on the connector, the HDMI chipsets at both ends of the connection must correctly manage the audio data. This is why we must use an HDMI-ARC port for the SONOS Arc or use an external manager, such as the ARCANA, if the TV does not support ARC.

I agree: Blue Jeans is a decent cable source.

So here is an update. Got a hold of a few more HDMI cables and did some testing. Here are the results:

Total tested 5 hdmi cables

Sonos HDMI - connection successful

Generic HDMI 1.5m - connection successful

Generic HDMI 2m - connection successful

Generic HDMI 10m - connection unsuccessful

Generic HDMI 10m - connection unsuccessful 

The cables and brands were all similar which leads me to believe that the issue is the length. Somehow Arc doest not get transported over the 10 meter cables?

Has anyone encountered this issue? If so, what kind of solution have you found? 

The problem is that I don’t think you can say “generic HDMI” without indicating which version of HDMI. 

I suspect that HDMI 2.1 cables of 10’ or 10m would work. Especially any that would be marked as “high speed” specifically.  Sonos is supposed to work on HDMI 1.4 cables, but at greater lengths, I’d want to up my game a bit, which is why I’m suggesting HDMI 2.1 cables. There’s been a lot of innovation/knowledge gained between those two specifications. 

But that’s a guess. You’re certainly on the right track. I’d be reviewing all the data on various websites about HDMI, including wikipedia and Blue Jeans Cables for more data. Wikipedia is often accurate, but not always, so it’s one source, but not the end all of everything, due to the nature of “crowd sourcing”. 

eARC requires higher bandwidth cables and bandwidth decreases with length. 10m requires very high quality cables. Price alone will not predict success. The cable manufacturer needs to have good quality control.

Use a certified cable. 

This is the second 10 meter cable I tried, which specified they guarantee ARC over 10 meters

Since you specified cable length in meters, you probably don’t live in the US. I was not very successful finding 10m certified cables. Likely anything I find will be from US based companies and may be difficult to ship elsewhere. I was able to find this cable. I know nothing about this company or availability outside of the US. I’m also not sure about their “certification” There is a specific logo associated with official certification. It’s an expensive test and the manufacturer is authorized to show its unique logo as proof of certification. I expect that cables passing this test would proudly display the logo.

happy udpate, received this cable today and it works perfectly.

I'll still try it out for a day or two before I run it in the ceiling and should be all good !