Apple Watch Series 12 and Ultra 4 Reviews Put Health Sensors and Delayed AI Audio in Focus

The hardware change starts with Apple’s new S11 chip, which adds a Secure Exclave for microphone data processing alongside a faster CPU, GPU and Neural Engine, according to The Verge. Apple also redesigned the health sensor array: larger ECG electrodes for better skin contact, photodiodes arranged in a ring to capture reflected light more efficiently, and larger, more power-efficient green LEDs. The Verge reported that the previous Apple Watch sampled heart rate once every five minutes when the wearer was not working out; the Series 12 and Ultra 4 now measure heart rate every five seconds, at rest and during activity.

Apple says the new Health Sensing System delivers “the most accurate heart rate sensing in a wearable,” according to 9to5Mac. The company cited a study of more than 1,000 participants and said the Series 12 achieved statistically better overall accuracy than every competing wearable it tested across workouts and daily activities. The Verge reported that Apple published a white paper comparing the watch with a Polar H10 chest strap and competing devices including the Pixel Watch 4, Samsung Galaxy Watch 8, Oura Ring 5 and Whoop. In The Verge’s own testing, the Series 12 stayed within five beats per minute of the H10 during two runs, a walk and at rest. ZDNet reported that its test found a .998 correlation to the Polar H10 strap. Apple’s claimed improvement in heart-rate fidelity is also behind the new Readiness score, which is available only on the Series 12 and Ultra 4.

TechRadar reported that Readiness uses sleep score, vitals data including temperature and blood oxygen, recent workout data and training load, and can incorporate workouts from third-party apps. Users need seven nights of sleep data to establish a baseline. Apple scores Readiness on a scale of 1 to 10, unlike Oura, Google and Garmin, which use a 1-to-100 scale. Craig Bolton, Apple’s Director of Fitness Technologies, told TechRadar that hardware advances made the feature possible. “It’s down to the evolution and the advancements we've made in the hardware technology, which has really brought about this to be the right time,” Bolton said. He added that Apple wants health and fitness features to be “simple and intuitive” while offering more depth for users who want it.

Apple is also introducing Audio Intelligence, a set of features that use the watch’s microphone and the S11 chip’s Secure Exclave to process sound and speech. Faster Shazam and Sound Recognition are available at launch, while Siri Recaps and Live Rewind are scheduled for later this year, according to Engadget and The Verge. Engadget said it tested Sound Recognition, setting it to detect alarms, appliance beeps and running water, and found it worked quickly. The Verge said several of the most interesting health and AI features were not available for review, and Engadget said the delayed features are central to the controversy around the launch. Apple has emphasized privacy protections, but Engadget reported that it could not yet assess how useful the features will be or how people around the wearer will react to the privacy implications. Users can choose not to opt in, Engadget added.

The exterior is largely familiar, though there are differences. The Verge wrote that the Series 12 has the same design, buttons, sizes and sensor types as earlier models. 9to5Mac reported that the Series 12’s display area is about 2 percent smaller than the Series 10 and Series 11, while the pixel count is unchanged and the casing is about 1 mm wider; it called the changes imperceptible in practice. The Series 12 comes in aluminum, titanium and ceramic. Aluminum finishes are Dark Bronze, Light Gold, Black and Space Gray, with Ceramic Shield 2 front glass. Titanium comes in Radiant Gold and Natural. Ceramic returns for the first time since the Series 5 in 2019, in Night Blue and Pearl White. The Ultra 4 comes in Natural and Black titanium.

Battery and charging are also updated. ZDNet reported that the Ultra 4 adds eight hours of battery capacity for 50 total hours with the always-on display enabled, and that 15 minutes of charging provides up to 18 hours of use. The Series 12 keeps a 24-hour battery estimate but charges faster, according to The Verge, which also said the S11 chip makes Siri AI queries faster and that a single pinch gesture improves one-handed control. Apple claims the Ultra 4 has the most accurate on-device GPS in a sports watch; ZDNet said it has not yet tested that claim.

Prices start at $390 for the Series 12 with a regular price of $399, and $780 for the Ultra 4 in Black with a regular price of $799, according to 9to5Mac. ZDNet recommended the Ultra 4 over the Series 12 for users who want the Health Sensing System, a larger screen and advanced GPS, but said Ultra 3 owners should upgrade only if they want the new health system and are willing to spend $799. 9to5Mac described the health tracking changes as the biggest upgrade to the Apple Watch’s health suite in years.