Hi
From my own experience when speakers start crackeling or making distorted sounds it tends to mean that they are failing and need replacing
These issues can come and go but they usually just need replaced to fix them once and for all!
Here’s a link to a replacement speaker
https://www.ebay.co.uk/itm/134000550806?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=TP1bhZJLSbm&sssrc=2349624&ssuid=0ACG7idPSQ6&var=&widget_ver=artemis&media=COPY
Also here is a guide that should show you how to disassemble the phone then remove the speaker
[link|https://m.youtube.com/watch?v=LhCX9eLQSI8|https://m.youtube.com/watch?v=LhCX9eLQSI8|new_window=true]
You only need to go up to the speaker part then perform what you just did on reverse to reassemble
Hopefully this helps
Any questions please ask
Thanks:-)