4 answers
It's going to be difficult because your soundbar doesn't have an audio output, what could work would be a subwoofer with line inputs and outputs, this for example:
http://www.rueducommerce.fr/m/ps/mpid:MP-A2FEEM20970194#moid:MO-A2FEEM33901968
-Solution 1: connect the TV's headphone output to the inputs of the subwoofer with this:
https://www.cdiscount.com/pdt2/3/1/8/1/700x700/auc8436021949318/rw/cable-prise-jack-3mm5-vers-2-rca-male-1m5.jpg
but you will have to adjust the bass with the TV's volume control...not great...
-Or solution 2:
TV headphone jack -> subwoofer line input (line IN)
Subwoofer line output (line OUT) -> soundbar line input (3.5 mm jack)
But you lose the digital sound.
The TV sound should not be turned up too high => saturation of the subwoofer and soundbar inputs => sound distortion, you need to find a balance to be above the noise floor but not saturate, you have to find the right compromise, advantage, the sound can be adjusted with the TV remote.
I call a spade a spade *
*in French in the text
http://www.rueducommerce.fr/m/ps/mpid:MP-A2FEEM20970194#moid:MO-A2FEEM33901968
-Solution 1: connect the TV's headphone output to the inputs of the subwoofer with this:
https://www.cdiscount.com/pdt2/3/1/8/1/700x700/auc8436021949318/rw/cable-prise-jack-3mm5-vers-2-rca-male-1m5.jpg
but you will have to adjust the bass with the TV's volume control...not great...
-Or solution 2:
TV headphone jack -> subwoofer line input (line IN)
Subwoofer line output (line OUT) -> soundbar line input (3.5 mm jack)
But you lose the digital sound.
The TV sound should not be turned up too high => saturation of the subwoofer and soundbar inputs => sound distortion, you need to find a balance to be above the noise floor but not saturate, you have to find the right compromise, advantage, the sound can be adjusted with the TV remote.
I call a spade a spade *
*in French in the text