Sonos announced the release of the Ace Ultra headphones priced at $449, which are available for preorder with shipping scheduled for September 29. ^[1] Researchers demonstrated that comparing Large Language Model calibration using global metrics such as Expected Calibration Error and Brier Score is confounded by differences in model accuracy. ^[2] Headphone Engine 2 includes redesigned Wi-Fi hardware and secure credential storage to allow the headphones to connect directly to and participate in the Sonos system. ^[3] Sonos states that the Ace Ultra is its first headphone built on Headphone Engine 2, which allows users to link the device directly to their Sonos system with a press of a button. ^[4] The Ace Ultra features new Sonos-designed 40-millimeter drivers and upgraded adaptive noise canceling technology. ^[5] The study found that ranking reversal is frequent, where models favored by raw metrics often cease to be favored once accuracy is controlled. ^[6] The study proposes an Accuracy-Controlled Evaluation (ACE) framework with three complementary views: Instance-Aligned, Distribution-Aligned, and Candidate-Aligned calibration. ^[7] Using the ACE framework across multiple benchmarks and model families, the researchers found that calibration advantages reported under raw global metrics weaken substantially after accuracy control. ^[8]