Your TV speakers suck. I'm sorry you had to find out this way, but it's important that you're aware. As TV manufacturers make ever-thinner TV sets, the space your speakers have to breathe becomes ever more tight and restrictive, the speakers inside your TV sound worse and worse by the year.
You could be cynical — "It's because the manufacturers want you to buy the matching soundbar!" — and there's a part of that which could be close to the truth. But. That doesn't mean you have to go out and buy the expensive matching soundbar option for your TV.
