My sub-woofer is 10 feet from the soundbar, and works well.
The sub-woofer has it's own on/off button located on it -- so doesn't have to be on if you are watching sports or normal TV shows -- and then turn it on for movies, etc.
Only problem we had was trying to use the Blue-tooth wireless function with the soundbar system -- the audio was not in sync with the television lips -- the sound lagged like a bad movie... but we have our soundbar under the television so we used the wire hookup instead. Ask the Best Buy sales person what's up with this...