If the TV has terrible speakers, then I would recommend an A/V receiver. It can be connected using the red/white RCA outputs from the cable box, and older stereo A/V receivers are typically online for cheap all the time.
You will need to connect some speakers as well. They are ALSO available online all the time. Maybe 50 bucks or so can get you much, much better sound.
Something like this...http://washingtondc.craigslist.org/nva/ele/5038031793.html
It was a good unit years ago, but wouldn't be ideal in a home theater today. But, for JUST stereo connectivity using analog red/white audio cables, you can get great sound which can fill a space quite nicely.
[Edited by AV_Integrated on May 22, 2015 at 4:04 PM]
- Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.