Diagnosis
The magnetic fabric grille is a dust magnet. Vacuuming or improper wiping can push dust into the speaker holes or snag the fabric.
How to Fix It
Remove the grille first. Gently pull from the bottom-center to detach the magnetic panel. Use a soft-bristled brush attachment on a vacuum cleaner on the back side of the grille to pull dust through, not push it in.
If That Didn't Work
For smudges or set-in dust, use a slightly damp microfiber cloth. Dampen the cloth with water only (no cleaners), wring it out completely, and gently wipe the grille. Let it air dry fully before reattaching.
Heads Up
Never wash the grille under running water or use chemical cleaners, as this can dissolve the adhesive holding the fabric to the frame and cause warping. Never vacuum the front of the exposed soundbar drivers.