A strange cracking sound started when I watched a movie and after some tests, I've discovered the need of the speaker to be changed.
The repair was fine, I'm happy with the results. The speaker have some kind of glue or tape to help the speaker to be fixed. To remove it need some effort but nothing difficult.
Nothing at all, the guide is excellent.
MacBook Air 11" (Late 2010-Early 2015) Right Speaker
T5 Torx Screwdriver
P5 Pentalobe Screwdriver Retina MacBook Pro and Air