Your TV speakers should be turned all the way down or off when you use a separate sound system such as a soundbar. Using them with the soundbar may cause echoes and the TV speakers do nothing to improve the sound.
Look at your TV's audio menu. If you can, turn the TV speakers off completely at the menu. Also see if you can set the analog audio output to "variable." This will allow you to control the soundbar's volume with the TV remote.
Answers & Comments
Your TV speakers should be turned all the way down or off when you use a separate sound system such as a soundbar. Using them with the soundbar may cause echoes and the TV speakers do nothing to improve the sound.
Look at your TV's audio menu. If you can, turn the TV speakers off completely at the menu. Also see if you can set the analog audio output to "variable." This will allow you to control the soundbar's volume with the TV remote.