My second pair of UB5 with the same fault, a buzzing noise or vibration that occurs when playing frequencies between 500Hz and 600Hz. It is unfortunate because except that failure I really like how they sound. But already with this are two pairs with the same fault … I do not want to risk again and that is why I am processing the return with AMAZON. I add the link with the frequency test.
If it’s a buzzing noise which may sound like distortion. The most common issue with vibration noises or buzzing noises is the speaker terminals have become loose. Also make sure the speaker cables themselves don’t have any loose parts. Some terminations banana or spades may have screws that could also become loose over time, even the expensive ones. So try to check for loose connections.
I actually had a very similar call yesterday and the customer tightened one of terminal nuts and it fixed the issue immediately.