Poor audio in one speaker - Mac

Question

I have a 2016 Macbook Pro 15" running macOS Sierra. The left speaker sounds muffled (it isn't outputting any treble) while the right speaker sounds perfectly fine.

For some casual debugging, I've done the following:

• Played with volume (no change)
• Used different audio sources (no change)
• Tried headphones (headphones work fine)
• Used Sound settings to change balance left and right, this magically made the right side sound just as bad. (This quickly lead me to believe it's a sound card issue)
• Used Applications > Utilities, Audio MIDI Setup to mute one side or the other and changed the format. This fixed the right side again confirming the sound card issue.
• Killed coreaudio and let it come back up. No audio at all after this.
• Reboot and reset pram, audio working as it was before (headphones good, left speaker muffled)

What else can I do to get both speakers singin' right again?

Answer 1

One thing in your troubleshooting leads me to believe that this is not a sound card issue: headphones worked. The sound card controls all audio, not just the speakers.

I see two possibilities (off the top of my head):

1. Your left speaker is damaged.
2. Your headphone jack has something in it that's causing electrical problems, or has a damaged connector. Make sure there's no debris jammed in there or other damage.

Also, electrical feedback from the bad speaker (if that's the case) could cause the behavior you saw with the right speaker. Again, I don't see this being an sound card issue at all.

Honestly, I would take it in and let Apple have a look at it. If it is hardware issue, they can repair it. If it's something in the software, they may have a solution.

Answer 2

Ok, just stuck a tooth pick into the headphone jack and 'Internal speakers' is accessible again.

Interesting, when it did change back both speakers where playing in stereo and at full volume (like the old days).

Then, macbook just crashed and restarted.

Having gone back into "Audio MIDI steup' it had gone back to mono signals. So, panned to the left is actually left 'mono coming out of both speakers', panned right is right mono coming out of right speaker only (not both like left).

Strange, its either 'Digital Optical' issues in the headphone jack, OR, its an update problem in High Sierra (im using late 2011 pro).

Answer 3

The issue can come from a high temperature under the speaker (CPU, GPU, battery charger input, etc.). This cause the treeble or the lowd diaphragm of the speaker (circular membrane) slightly melt away, soften and doesn't work properly anymore. Then the speaker cannot transmit correctly the sound. The solution is to replace the speaker and to find why the temperature increases a lot. Sometimes fans must also be replaced if they show signs of ageing or simply cleaned by removing dust inside.