Not sure if it's been mentioned already, and sorry if this is a dumb comment, but just check that the external fabric is not adhered to the speaker membrane anywhere. Often they're kinda stuck here and there and can release by themselves but sometimes don't.
That would deaden a panel.
You'll know by looking side on to see if the fabric is flat or not.
That would deaden a panel.
You'll know by looking side on to see if the fabric is flat or not.