Chosen Solution
I have the Touchbar version of 15" 2017 Macbook Pro. About a year ago my left speaker started losing treble. It came to a point where it it was too distracting so I brought it in to the Apple store for repair (under my credit card’s extended warranty). Now a year after the repair, my left speaker is losing treble again! I cannot afford to have it fixed again because I no longer have warranty on the device. Has anybody else encountered this with their Macbook? There is no apparent damage of any sort nor do I ever play loud music from the speakers. This issue exists on both OSX and Windows 10 bootcamp so I know it’s not a operating system issue.
I think you need to do some testing here to isolate out what’s really failing. I don’t think Apple did anything to your system! They may have just blindly replaced the speaker but that was not likely the issue. The speaker design uses both a tweeter (high frequencies) and a woofer (low frequencies) speakers. each is driven by separate circuits via the Digital Audio Converter (DAC) which converts the digital signal into an analog signal the speakers need to work.
So did you blowout the speaker by over driving it? Or is the connection to the logic board and the pathway to your DAC logic failing, or lastly is the DAC its self failing. You’ll need a good Audio Test - Tone Generator to really compare your internal and external speakers so you can create a clean tone at the frequencies you are concerned with. I would start off by using a wired set of speakers to plug into the headphone jack (don’t use Bluetooth as that uses a different circuit pathway and DAC logic) Does it also have problems with the high frequencies with the same side? Use the Sound Control to bias which speaker is active. Once you know if the internal speaker unit or the Connection/DAC logic that has failed you can then figure out the next steps.
