Dust, dirt and/or water damage could quite easily make your speaker sound distorted or poorer quality than it initially did (I presume this is your complaint). If you have any tools use a small ++plastic++ needle nose tool to ++gently++ clean your speaker ports, being careful not to damage them. Avoid using compressed air, especially at high pressure as this could damage the speakers further, a light blow (of your breath) does help clear a debris, after your clean with the needle nose tool. A microfibre cloth also is helpful to wipe out the speakers.