Default HTC One M7 top speaker is quieter

Hi,
I've just recieved back my HTC One M7 from Polish Regenersis. They refused repair my speakres, because I had a little bit cracked screen on edge (under back button). No comment.

Google told me that this problem (quieter top speaker) have a lot of people. Could you help me to solve my problem? I tried to update Chrome, but still it doesn't work well.