You’d need something to generate the HDMI-ARC/eARC that the Beam requires. Check out the HDFury Arcana. It would send audio back to the Beam and video onwards as conventional HDMI to whatever you wish. 

Hi @ViRuS 

@ratty is correct that the Beam has to have an ARC signal from a TV or projector, but the Arcana is an expensive solution. I have a free one for you:

You mentioned that the PC is the main input source for both the TV and projector. If it were the only source, you could simply connect the Beam to the optical output on your PC (if it’s not a laptop, it probably has one) using the optical adaptor that came with the Beam. That way, the audio is played to the Beam regardless of which screen you use, or if you use both, or neither. You will need to tell the computer to utilise the digital optical output (SPDIF) by clicking on the volume control, then the current output (in Windows anyway, I’m not sure about Macs). You will also need to make sure that your audio codecs/filters only output Dolby Digital or PCM (and soon DTS) as the optical connection will not carry anything of higher quality.

If you use this method of connection and use an input other than the PC, you will only get sound from the TV’s speakers.

If you want to use a remote to control the volume, you’ll need to teach the Beam the remote codes. Instructions are on our Control Sonos home theater with your TV remote help page. I recommend using an old remote that doesn’t belong to either the TV or the projector as they will respond to volume controls if no audio device is connected to them (assuming the projector even has speakers).

I hope this helps.