I too am hearing impaired with a wife that needs a lower volume that I. Here is my solution:
My system Samsung TV 4K UHD (JS8500) and new Samsung 7.1.4 Harman Kardon soundbar (HW-Q90R).
Basically, I wanted to connect my new Bose headphones (Bluetooth) into the system so my wife can adjust the sound to her comfort level and I could adjust the headphones to my level – the key is being able to do that simultaneously. Optical connection (forget HDMI ARC or regular HDMI for this solution).
This is how I solved it inexpensively for around a $100:
Optical connection from TV Optical connection to Digital Optical Audio Splitter, in port (mine was a 1x3; 1 in port, 3 out ports) in port. Make sure you get a powered unit for better signal consistency. Cost me $22.00 from Amazon. (note: I used J-Tech Digital Premium SPDIF TOSLINK Digital Optical Audio 1x3 Splitter)
Optical connection from Optical out port #1 (of splitter) to Optical in port on soundbar
Optical connection from Optical out port #2 (on splitter) to Optical in port of Blue Audio Transmitter for TV (it also has a 3.5mm connection for wired as well). Make sure you get a powered unit (mine could power BT 4.0 to 2 headphone sets and each could control volume undependably from each other). Cost me about $69.00. I used MEEaudio Connect Universal Dual Headphone and Speaker Bluetooth Audio Transmitter for TV (AF-T1)
Simply pair the unit.
We now have a system that my wife can control the volume of the soundbar system; and I can control the volume independently in my headset – both work simultaneously and great!!