Answer to "Left speaker is not the same as the right speaker output"I have found that it is possible to fix an imbalance between speakers by loosening the screws at the back of the computer under the offending speaker. Play something, lay the laptop on its keyboard with the screen hanging over the table so that the back of the computer and the screws can be seen. loosen a screw at a time while listening to the sound. You may find quite a remarkable improvement ! Tighten them all up one at a time until the sound worsens again, then, loosen once more - or remove that screw totally. You could stick the screw in place - but loosened - with a drop of nail varnish. This a a temporary fix - but, it works for me until I can get a new machine. Replacing the speakers did not help by the way, but my screw trick - found while I did the replacement - did.
Answer to "Is my MacBook's Internal Speaker Blown?"The IFixit guides are essential for performing any part replacements - but read and follow them with care - and read the user notes too. After replacing my speakers, the left one is quiet - but I think that is a software thing - I’ve not fixed that yet …