Beamer is a projector, correct?  Assuming that’s correct, here’s my thoughts.

1 - You could use an HDMI matrix like this .  The idea is that you can use the matrix to switch between 4 different sources on two different displays.  Then you would use optical output to send audio to the Beam (via HDMI-ARC/optical adapter that comes with the Beam).  I would not use HDMI-ARC as you likely don’t have the capability with your projector.  I am not exactly sure how the matrix I linked to decides which source audio to use, but it should work for your case regardless.

2 - No, you can’t use the same sub and surrounds with both a playbar and beam.  The speakers are bonded together and would need to be reconfigured and retuned via Trueplay every time you switch between playbar and beam.

Thanks Danny fot you input 

the thing I do not well understand is the audio through the hdmi arc optical adaptor. 
 

step by step 

SOURCE 1 /Epson tw 7000 beamer → HDMI cable to switch 

SOURCE 2 / Sony tv → Hdmi cable to swith 

SWITH - HDMI cable to SONOS BEAM 

but then for the audio adapter ? 
Having said this in my set Is a decoder aswell as an Apple TV box 

the set Up now is that Netflix comes from the Apple TV box - straight hdmi to  tv - Sound is HDMI from tv to SONOS BEAM . 

newt step is to include a Beamer 

it seems complicated to me. 
 

So your sources are  decoder and Apple TV.  Your ‘sinks’ are TV and projector.  You can think of the Beam as a sink in this case too since it receives the audio.  The matrix will go in between source and sink to send the right audio and video to the right sinks.

 source → matrix → sink

decode/apple tv → matrix → TV/projector/Beam

The matrix extracts the audio signal through it’s optical output to an optical cable.  The other end of the optical cable connects to the adapter provided by Sonos.  The HDMI end of the adapater connects to the Beam.

FYI, the Beam doesn’t read a normal HDMI audio signal, it only reads HDMI-ARC (Audio Return Channel).  The ARC audio signal actually flows in the opposite direction of normal data though.  It’s usually a TV that generates the ARC audio signal but that isn’t going to be a consistent source of audio for your situation.  That’s why it makes more sense to use an optical connection, via the adapter, since a matrix like what I mentioned should always being sending an audio signal.

Allright Danny 

Thanks a lot, this seems pretty clear to me now