macbook prospeakers
Macbook Pro 2016 15" model. The speakers often go from perfectly clear to very noticeably muffled when adjusting the volume. It often happens when turning the volume up – but it'll still be at reasonable levels. It gets muffled immediately as opposed to slowly degrading in quality which leads me to believe it's not a problem with the speaker slowly deteriorating.
It usually goes away after a few restarts.
Is this normal? How can I debug this further?
This is a well known issue of macbook pro since 2009 and it effects even the latest model. The reason being the macbook speakers are not designed to resist heat. If it has been working for hours over 100 degree (or 30 some celsius idk) the rubber will melt and tear under high volume. The left speaker will less likely to have such condition since the ventilation is better on the left corner. Why does Apple keep using this type of rubber? I guess they want the rubber to be bouncy enough to make decent sound while keep the cost low. Besides Apple products are never built to last anyways. All you can do is to cool your macbook while using it or you can try to use superglue to cover the rubber, which would make it tougher but the sound will be worse. For a quick fix, you can put gel around the rubber or just the place of the torn mark(s). Take a look at this picture. This is how I did it.
I had this issue on a 15" 2017 MacBook Pro, three times over the course of roughly three months.
Apple issued two top case replacements, which includes both speakers–yet each time, a speaker would fail.
Apple finally issued a logic board replacement with a top case replacement. This, so far, has cured the issue.
Best Answer
I've experienced this issue and after a complete re-install and every troubleshooting regarding software tried out, I handed it in at an AASP. They determined the issue to be hardware, and exchanged the top case (which also means no more sticky keys).
So my best advise is, take a backup and go visit your local AASP.