Hi Molly! The Samsung HW-B400F and Samsung HW-C400 are both 2-channel soundbars with a built-in woofer designed to enhance your TV’s audio, but there are a few key differences.
The HW-B400F includes HDMI (ARC) connectivity in addition to optical and Bluetooth, which allows for a simpler one-cable connection to compatible TVs.
The HW-C400, on the other hand, connects using optical or Bluetooth only and does not include an HDMI (ARC) port.
The HW-B400F offers more connectivity options and easier integration TVs, while the HW-C400 is a more basic setup. ~ Samsung Solutions