Remove the left ear cover by tugging it around and popping it off. The hardest part will be getting them back in. This will be the second hardest part: removing the screws on the left speaker.
Gently, it won't break easily but just be careful. Once the battery is out unhook the coupling. Shut off the headset, unplug it, and remove the battery by popping off the right outer ear cover and using the Flathead to pop the battery out by the tiny lip on the top. and a flathead to actually fix the issue. One TINY Phillips screwdriver to get the screws under the speaker cover out.
Ok, it is an easy fix but you are going to need two screwdrivers, and something to cover speaker. Of course pushing the power button around would mitigate it for a time.
I've had the power button loose for a while, like a month or two, and it was causing the volume in the speakers to cut out or dim. Was looking for a place to put the fix up. Ha finally! I had the same issue and just fixed mine.