Probably the sound dampening material inside at one time or another got wet. You can try, if possible, open the cabinet or remove the woofer to gain access to the inside. And even if there is no sound dampening material, try either spraying Ozium available at Auto parts stores, or fresh coffee grounds. Coffee grounds absorb odors, Ozium eliminates via masking and neutralization.
That is my guess without smelling or seeing the speakers.
Good luck.
That is my guess without smelling or seeing the speakers.
Good luck.