Chosen Solution

I dropped my iphone 6s the other day and now the loudspeaker doesn’t work. I swapped loudspeakers with my parts phone and it still doesn’t work, but the “broken” one works on the parts phone. I don’t think its software bc i restored the phone. What else do i need to replace?

Starting with the speaker was the logical choice. Next, I would try the Lightning Flex, you can check out this guide. However, if that doesn’t work, then the logic board may have been damaged due to the drop. You could inspect the connector area as there are a lot of tiny parts surrounding it but the issue could be anywhere in the Audio/Amplifier circuit and would ultimately need to be looked at by a micro-solderer.