DIAGNOSIS The speaker's bass radiator on the bottom is likely obstructed. This product uses the surface it sits on to amplify bass, and if that surface contact is compromised, audio quality plummets.
FIX Immediately check the bottom of the device. Remove any stickers, debris, or felt pads that may have been added. Ensure it's sitting flat on a hard, stable surface like a shelf, countertop, or table. Don't place it on a soft blanket, pillow, or uneven surface.
IF THAT DIDN'T WORK Dust or pocket lint can get sucked into the speaker grille. Power it off, then use a can of compressed air to gently blow around the entire fabric surface and the bottom port to dislodge any blockage.
HEADS UP Never use liquids or cleaners on the fabric. If the muffled sound persists after checking placement and cleaning, the internal speaker driver may be physically damaged and the unit will need replacement.