Why iPhone 7 Don't Have A Earphone Jack

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.”

Sound quality

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.

soundwave

Continuous sound wave (red) and bits of data sampled (blue) for storage as digital audio (Image CC BY-SA 3.0: Wikimedia)

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.”

High-resolution audio

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.”