Does it have to be a soundbar as the form factor? I mean they are quite compact and can fit into the room quite so they don't stand out, in front of a flat screen TV perhaps.
I don't know if they have features such as bass cut or graphic equalizer, but what I do know that the ones that are in the normal consumer price level tend to have small speakers so they really don't reproduce much bass anyway, but are still better than the speakers integrated into the TV.

Before soundbars were invented, people just bought an amplifier and speakers. Nowadays those amplifiers are called AV Receivers (AVR), as they are capable of decoding multichannel bitstreams as well. They should have more settings for tuning the sound, and you can choose which amplifier you want and which speakers you want and how many speakers you want (while two speakers are good enough for a simple stereo setup, home theatre people may enjoy seven speakers and a subwoofer or even more).

If the soundbar/AVR and TV are both same brand, they usually can talk to each other quite well using single HDMI cable for feeding all audio from TV and for control, so you only need the TV remote to control the whole system, it's like an add-on you don't really need to care about much.

There are also good comfortable headphones available, both wired and wireless, it just depends if you want to use them or do other people need to hear stuff as well.

For person that is losing their hearing (and continuing to do so), wireless headphones seem a better option.

Was in the same predicament being hearing impaired myself. Ended up getting the Edifier R1700bt speakers which have blue tooth so you can use your phone and other devices. They look nice too and sound great, price was about 130.00 on the Edifier site when I got them back in May.

Ok, frist thing. Why are they having a hard time hearing spech?
Not loud enough? If so a good sound bar can help that.
If its a problem with too much background noise a sound bar might not be a good idea unless you can try it out in person.

Here in the us most sound bards are junk, except the ones your tv sets on. Even then they armt that good.

Also how old is the person with the problem? If they're older they would probably want something simple.
Wireless headphones might not be the answer for more elderly person. If they get disconnected they may have a hard time fixing it.

What about a speaker setup with the speakers closer to where they sit when watching tv?

Not sure of the model, but my Samsung TV has options for sound mode including "clear voice", and generally, you'd use external speakers to get more base - may be worth going through the TV menus