Image: Hector Martin/Twitter
The speakers of a MacBook Air can be damaged just by playing a really, really loud song, and a loud sound for 40 seconds, according to a researcher who pushed the laptop’s speakers to their limits.Hector Martin, an independent security researcher who focuses on Apple products, said he was able to damage his MacBook Air powered with the company’s M2 chip in a recent experiment by “overdriving them with settings and content they were not designed to play.”
In a Twitter thread, Martin explained how he did it. Martin said he used a song made by Dan Worrall aptly called “I Won The Loudness War” as well as a 40-second “sine sweep,” which is a tone that goes up in frequency to see how a speaker responds to it. “The song was just for fun after I killed one speaker, because it's possibly the loudest ‘real’ song in existence,” Martin told Motherboard. “The issue here is that on these machines the OS has full control over those things and the amp can go louder than the speakers can handle, without the driver limiting things.”On his GitHub page for the project, Martin wrote, “my conclusion is that the tweeters are the major damage risk, and that damage occurs fairly quickly, even with just 40-second sweeps. If this is thermal, that suggests even short-term power excursions are dangerous.” (Martin believes the songs and the sweep could probably damage other laptops made by other manufacturers too.)A tweeter is part of a loudspeaker which is designed to play high audio frequencies. Martin said he damaged the left tweeter just with the 40-second sine sweet, while it took playing I Won The Loudness War to damage the right one.
“The failure mode for the tweeters seems to be a severe drop in volume, except for a small band of improved reproduction (that varies). My theory is that this is thermal damage, i.e. the tweeter melted itself and seized up. Left: dead tweeter; right: possibly-damaged but still functional tweeter,” Martin wrote on Github.
On Twitter, Martin wrote that “the good news is these speakers are stupidly loud anyway, so I don't think it's going to be a major issue to max out lower than macOS (and I've seen speakers die with macOS too, so they push them too hard).” Martin performed his experiment on a MacBook Air where he installed Asahi Linux, a version of Linux that he is building specifically to run on Mac computers that run Apple’s own processors. That being said, Martin wrote that he thinks playing “I Won The Loudness War” could cause damage to a the MacBook Air M1, and the Pro M1 running MacOS, and perhaps even to a newer MacBook with the M2 chip. Martin told Motherboard that he did the experiment to figure out how MacOS protects its speakers from getting damaged, and then port those techniques to Asahi Linux.
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“The speaker amp settings and speaker safety are fully controlled by the OS. macOS uses a sophisticated speaker safety model that estimates speaker temperature to keep them safe. We need to figure out what is safe for Linux, so I was doing some tests from there, but (I now figured out) I was wildly overdriving the tweeters, which is how I killed them,” Martin told Motherboard. “Asahi Linux has had speakers disabled for a long time now because we knew this could be a problem.”Martin said he believes that Apple should have designed its MacBook speakers to be able to withstand loud sounds even if the user is running an operating system other than MacOS.“But the design is what it is, and we're going to try our hardest to make sure nobody damages their machine without trying very, very hard (with multiple layers of safeties),” he said.Martin noted that the woofers, which produce the bass and low-frequency sounds in music, did not appear to be damaged in the experiment, although he said the experiment did “something” to them, “and it affected the rattling, but it's not an obvious kill like it is with the tweeters.”In other words, more tests are needed, but first, Martin said he is sending the laptop to Apple for repair. “Good thing I have AppleCare!” Martin wrote on Twitter. UPDATE, Sept. 15, 12:58 a.m. ET: The story has been updated to clarify how the speakers can be damaged, and what Apple products may be at risk.