I had the same issue with my Maven pro tablet. It eventually got to the point i could barely hear it even with my ear next to speaker. I initially tried master reset but nothing changed. I removed the back and found that my speaker was a little dusty but had metal shavings beld magnetically all over the front of the speacker. wiped it clean with a soft dry towel and now they work like new again.
I was having issues with the speaker on my rca tablet. I could barely hear anything out of it even when turned up all the way. Due to another issue I was having a master reset did not help with the sound. Upon opening up my tablet I found the speaker was covered in dust and metal slivers that were being held there as if magnetized. With a soft dry cloth I gently wiped off the speaker until it was completely clean. The sound now works perfectly again.
