Best answer by Airgetlam
If you poke around in the Home Theater area, you'll see a lot of folks complaining about this issue on Samsungs in particular.
Yes, you could connect it via the adapter with an optical cable, but I'm not sure it would make any difference.
From what I can tell, here's some suggestions. Not being a Samsung owner, I can't vouch for their value.
1) Make sure the TV has the latest firmware on it.
2) Turn off any "extra" processing that the TV might be doing to the sound signal. Extra wide, extra surround, extra voice, anything at all. You want the TV to be passing through data as close as possible to what it receives. Any extras that get added to the sound just means more processing time taken by the TV set before it sends the signal back out on the HDMI-ARC channel.
Many people seem to have gotten around the issue by removing the TV as part of the equation for sound processing. They've purchased an external HDMI switch which separates out the sound to an optical connection, which they then send to the Beam. They lose the ability to use HDMI-CEC commands, but they get sound in sync with the video (which leads me to the conclusion that it's the TV set that's causing the issue....despite people wanting to blame Sonos. Quite simply, the Sonos can't play anything before it gets received by the device, and it's the TV that's delaying the signal).
Hope this helps.