We had a set up like that with the original Bose system until a few weeks ago! We purchased this converter: link.
Then we ran an optical cable from the TV into the converter, and 2 RCA cables from the converter to the Bose subwoofer. Plus of course connected the small Bose controller/receiver to the subwoofer as well.
You may need to adjust the digital audio delay on your TV to sync it with the video.
We had a set up like that with the original Bose system until a few weeks ago! We purchased this converter: link.
Then we ran an optical cable from the TV into the converter, and 2 RCA cables from the converter to the Bose subwoofer. Plus of course connected the small Bose controller/receiver to the subwoofer as well.
You may need to adjust the digital audio delay on your TV to sync it with the video.
Cheers!