Question Poblem with the posterior loudspeaker in Xpeia Active (Middlecover?)

A hardware problem. The loudspeaker. When I removed the sticker to unlock the boot loader without loosing DRM rights I used a hair dryer to rip the sticker off heating the glue to make it easy... I think that heat damage the posterior loudspeaker, because, since then... The sound is awful... I need to know the right thing to do to repair it myself, how do I know if the failure is the Middlecover (where the sound box is) or is it the speaker itself that it is damage (inside)? Where's is the speaker? How does it work? Spare Parts? I'll appreciate any help you can give me in here guys... Thanks.
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