The headphones are said to rival the likes of Bose and Beats by Dre which is odd, seeing as Apple owns the latter brand. Apple has been working on the product on and off since they started their efforts, dealing with issues similar to the ones they went through during the development of the HomePod. Sources say there have been multiple redesigns and note it's possible Apple could change the design again or even scrap the project altogether.
Apple's wireless speaker is coincidentally also an example for Apple opting to develop an audio product outside of Beats, which it acquired for $3 billion four years ago.
Apple is working on new high-end noise-cancelling headphones following the success of its AirPods earbuds. The HomePod's sound won glowing reviews this year and Apple is already preparing other audio accessories like upgrades to AirPods. The company has also reportedly run into "development challenges" that could jeopardize that target ship date. Whatever the company is cooking up in the headphone space will likely have a premium look to it, especially with Apple targeting audiophile-grade performance. AirPods and a revamped Apple Watch are the only major products it's released in this category over the previous year. This means that Apple might price its headphones in higher range, otherwise it might end up harming one of its own brand. The wireless headphones finally hit the market in December 2017. "Apple's path to leadership in the category is helped by disruptive pricing, brand resonance, and excitement over the W1 chip, which significantly eases Bluetooth connections to iOS and Mac devices". Both Bose's popular QC35 II and Beats' Studio3 wireless headphones cost $350.