Samsung Galaxy S3 speaker connection flickering, loose contact

**Issue** The issue happens on my samsung Galaxy S3 model SGH-I747M. The loud speaker doesn't work anymore unless I "hit" the back of my phone until it work again. But then I need to be VERY careful, because any touch to it can cause the speaker to stop working again. For instance, just putting the phone on a table can make it stop again. Example : I put some music to play without headphone. The music is playing in the app but there is no sound coming out. I hit my phone once and the sound start coming out then I put my phone on a desk and the sound stop coming out again even if the music is still playing in the app. I hit the phone on the desk a few times for the sound to come back. Since hitting the phone temporary fix the issue, I suspect the speaker connection is loose. **Issue solving** Playing music here was the easiest example, but alarm clock, phone ringning and every others apps that use the lound speaker does the same. Therefore, I suspect a physical problem. However, I don't know where the loose is. [Here](https://www.youtube.com/watch?v=uVuehXeT5YQ) they show how to change the speaker on the phone. Changing the speaker would solve the issue only if the loose is within the speaker part. If it's before that, then it's won't solve anything I guess. **Question** Is the loose within the speaker part or within the rest of my phone? If you can't tell for sure, then what are the probability for the issue to be within the speaker part? Any other advice are welcome.