I had a recent experience with my Spica TC60's. The noise I experienced was a buzzing or raspy sound and the vocals were sort of nasal sounding. It was actually the banana plugs on the speaker post. I removed them and put bare wire in the post and all the noise was gone. Spades are better as well as bare wire compared to a banana plug that is not snug. They will vibrate and make a noises that will make you think your speakers have a problem. I'd start there.
Then check the tubes for microphonics. If it is a tube preamp or power amp turn the volume down and tap each tube with a pencil eraser lightly. If it comes through your speakers you have a microphonic tube. If no tubes check all your connections. If it is the speaker,.... it could be the internal wires resting on the cone of the driver internally and vibrating. Not likely but possible if you have been in it recently.