I have an aftermarket soundbar from the previous owner. Not sure on the brand, but it has infinity speakers in it. I had the same annoying rattle, and my wife (girlfriend at the time) found the fix. She shoved a penny in between the plastic light cover and the padding. After I added a 12" sub, I upgraded it to a nickel. It hasn't made a sound in at least 5 years. No wonder I married her... Hope this works for you.