The speaker issue is only coming from the top, not the bottom. Hold one quiet with your hand, and see if the other is the source of the issue then vice versa. There needs to be extra adhesive on the speakers, because from taking it apart they are not factory flush again, otherwise, they are rattling around and that is why it sounds crackly, especially if they are not perfectly tight within the housing.
Chances are as well, if your playing it at full, you always run the risk of blowing out your speakers. This also could have happened if heat was applied during the whole process to remove any of the adhesive from the pieces. Just food for thought, you don't run your car speakers at full volume, or any speakers for that matter, because you blow them out. Your phone shouldn't be any different.