For what purpose?   Both the Arc and Beam are soundbars designed to be connected directly to your TV and will only play the front left, right, and center audio channels.  The Beam cannot be configured to play the rear surround audio channels if that’s what you were thinking.

You could have the Arc in the front and a Beam setup as a second room grouped with the Arc.  However, the Beam will not be in sync with the Arc, playing slightly behind, giving an echo.  This is while playing TV audio, not streaming music.

You could also use a few different combinations of HDMI switches/optical extractors/etc to send audio directly (wired) to the Arc and Beam, but it may not be perfect sync, you’d have wires to the back of the room where the Beam is, and you be limiting the audio formats you can play.