Chosen Solution
I bought an iPhone 11 with a speaker which sounds like it was water damaged, nothing was wrong with the phone apart from the speaker was very distorted on high volume. I replaced the lower speaker today and it still has the same problem. What could I do?
Assuming that the replacement speaker is good, have a look at the holes where the sound comes out of. There are grills there and they very commonly get clogged stopping the sound to come out ok. Scratch the debris off with a pin and use some canned air if you have some. A toothbrush alsk works great as a finising touch. Don’t put too much pressure with the pin, and don’t use someting strong that regular computer air cans