Apple’s new iPhone doesn’t have a headphone jack, only a Lightning port that’s also used to charge the battery.
In-ear sound comes from the EarPods or other headphones with a Lightning connector, via a Lightning-to-3.5mm adapter (included) or wireless headphones such as AirPods (sold separately).
Why did Apple remove a common audio connector?
The 3.5mm jack is over 50-years-old and doesn’t do much besides carry an audio signal. It needs its own power amplifier and digital audio converter, which can be built into headphones, so removing the jack makes room for other things, such as a second speaker.
As Apple marketing chief Phil Schiller said at the iPhone 7 launch, “Maintaining an ancient, single-purpose, analogue, big connector doesn’t make sense because that space is at a premium.”
But does making room for what Apple thinks we want (such as a vibrating Taptic Engine) outweigh the inconvenience of not having a widely-used socket — and being forced to buy yet another expensive adapter to listen to music while charging?
Schiller said the decision to drop the 3.5mm jack was down to courage. However, even if you accept that the change was brave, “courage” doesn’t clearly highlight the advantages to customers. Apple should have used another word to explain the iPhone 7′s lack of headphone jack: progress.
“The headphone jack is really quite limited,” says Dr Joshua Reiss, head of audio engineering research at Queen Mary University of London. “For the person who wants really great sound, using the Lightning port is much better than using the headphone jack.”
The Lightning port is superior to a 3.5mm jack due to how it carries audio signals. “The big problem with the old headphone jacks is that they’re analogue technology,” Reiss explains. “Modern audio formats are all digital, and have been for a very long time.”
Sound consists of waves transmitted as vibrations through a medium such as air. But while an original source — like sounds from musical instruments — produce a continuous wave that contains infinite information, your auditory system (ears and brain) doesn’t need to sense actual waves to perceive sound as a continuous stream.
Just as movies are made-up of a sequence of still images shown in quick succession (usually 24 frames per second), audio is recorded by taking snapshots of a wave at regular intervals, allowing those samples to be stored as bits of digital information.
For playback, those digital bits are converted back to a wave representing the original recorded sound, or “analogue.” This is achieved by speakers that vibrate air to create a continuous wave that can then be detected at your eardrums. One drawback of a 3.5mm jack is that its digital-to-analogue converter alters the audio signal prematurely, before it reaches a headphone’s speakers, which can allow data to be lost from a recording.
“Generally, the jack itself will have had some audio degradation just getting the audio,” says Reiss, who recommends that you plug headphones into the digital port. “Your best option at the moment is to not use the adapter, but have good headphones that can use the Lightning connector directly.”
For audio that sounds closer to an original recording, you need to go beyond CD quality. “For almost all people, most music, you wouldn’t hear a difference,” says Reiss. “But there are benefits, and for audiophiles these things become more important.”
CDs store 16 bits of data per sample at 44,100 samples per second (44kHz), but sound can also be recorded with 24 bits at a higher frequency of 96kHz. And while iPhone 6 hardware supports 24-bit/96kHz, software such as iTunes and Apple Music don’t transmit that to a 3.5mm jack. As streaming services like Tidal offer hi-res audio, iPhone 7 owners could soon get better sound.
Whether we can appreciate beyond-CD resolution has long been a subject of debate, partly due to conflicting scientific studies.
CD quality should be enough to capture a realistic sound and most humans can’t detect frequencies above 20kHz (which is why you can’t hear dog whistles). At the same time, some claim that hi-res audio sounds crisper or more intense, and brain imaging shows that individuals do respond to high frequencies.
As a consequence of the confusion, parts of the audio community cherry-pick whichever study supports their agenda. For example, manufacturers of high-end audio equipment obviously have a vested interest in saying we’re able to tell the difference between ordinary CD quality and hi-res audio.
Reiss recently settled the argument by bringing all the relevant research together, a meta-analysis of 18 studies that included 400 participants from 12,500 experiments. “Putting them all together, it showed that people did definitely hear a difference,” he says, adding that flaws in several tests suggest the effect isn’t as subtle as it seems. “There were many indicators that our ability to hear this difference might be even stronger than the studies.”
While any headphone connector — whether 3.5mm or Lightning — can affect audio quality, Reiss emphasizes that the most important factor is the speaker inside each headphone, which turn a signal back into sound. “That’s usually the weakest link in the whole chain,” he says. “You might have an amazingly high resolution, fantastic representation of the signal, but then you play it back over really bad loudspeakers.”
One criticism of Apple’s decision to drop the 3.5mm jack from iPhone 7 is that you can’t listen to music while charging (without a second adapter). This is deliberately inconvenient because the company is aiming to push people away from cables. As Phil Schiller said, Apple has “a vision of how audio should work on mobile devices… wireless.”
Wired vs. Wireless
Wireless headphones like Apple AirPods communicate with audio players through Bluetooth technology. Recent devices use version 4, which is vulnerable to loss of audio — drop-out — if two devices aren’t properly paired.
“Bluetooth standards are much better than they used to be, but still far from what they could be,” says Joshua Reiss, who believes the next standard — Bluetooth 5.0, available in 2017 — could fix many current issues. “Your connection might always stay on and you might not need to do anything to make the Bluetooth device connect, so the sound drop-out should go away.”
The new AirPods have a “W1″ chip that helps pairing, but they’re ultimately built on ageing tech, and it’s less reliable than wired connections. While this might not bother early adopters, others may want to wait for iPhone 8, which should include Bluetooth 5.
Lightning has some advantages over wireless headphones, such as bandwidth — the amount of data transferred over a connection — measured by the number of bits moved per second. Bluetooth 4 can transfer 25 megabits per second (Mbps), whereas Lightning can handle almost 20 times as much, 480 Mbps.
Greater bandwidth enables a connection to carry extra information, which will mean interesting new features in future phones. A signal could transmit multiple audio channels (more than two-channel stereo) for surround sound, for example, or your headphones could adapt its output based on geolocation data collected by your phone, automatically activating noise cancellation in a crowded environment.
Lightning vs. USB
Although removing the headphone jack involved both courage and progress, Apple was wrong to replace it with Lightning.
During the iPhone 7 launch, Phil Schiller presented a misleading figure — there are 900 million Lightning-enabled devices — to imply that people prefer the port, making no mention of other wired connectors. This doesn’t match Apple’s message that the company ditched the 3.5mm jack “to do something new that benefits all of us”.
By “all of us”, Schiller was only referring to people who are fine with being locked into Apple’s ecosystem — not those who have, say, an Android phone and iPad, customers who would rather not need different cables for each device.
If Apple truly wanted to benefit everyone, it would switch to USB Type-C — a connector the company already uses in its MacBook computers. USB-C is found in smartphones like the Google Nexus 6P and Moto Z, and — like Lightning – it’s a digital connector with a bandwidth of 480 Mbps (for standard USB 2.0).
Why stick with Lightning? Because it’s proprietary technology, so third-party manufacturers must pay Apple for the license to use it. (For people who want to future-proof their headphones or want them to work with non-Apple products, it may be worth skipping iPhone 7 and seeing if next year’s model switches to USB-C — unlikely — or uses Bluetooth 5.)
Removing the headphone jack is inconvenient in the short-term, but Reiss believes the long-term benefits make it worthwhile. “It’s a bit shocking to some people, it’s doing away with the technology that people are very comfortable with, and also very frustrating for people who’ve invested in headphones using the 3.5mm jack and don’t want to use an adapter.”
Ultimately, the reason Apple replaced the headphone jack is because the benefit outweighed the risk of alienating a few existing customers.
“It’s a happy mix of something that allows them to sell new products, to license anyone who wants to use their Lightning,” says Reiss. “At the same time it’s also good technically, for improving audio quality.”