I have been using a matched pair of F1 812 with F1 Subwoofer purchased in Oct 2016. The system has worked flawlessly but during sound check for a recent gig, I noticed for the first time that the upper 10' speaker in one of my Subwoofers had a buzzing/distorted sound. EQ switch for both columns were set to Full Range selection.
When volume is set at half or less it isn't as noticeable but any higher will cause that speaker to buzz/distort.
What may be causing this issue?
Your assistance/advice is much appreciated.