The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
No source gives an exact on-sale day. Sony's own press release of September 7, 2026 (https://sony.mediaroom.com[2]/2026-09-07-Sony-Electronics-Introduces-WH-1000XM4C-M4-2nd-Gen-Wireless-Noise-Cancelling-Headphones-and-Updates-Popular-Mid-and-Entry-Level-Wireless-Headphones-with-WH-CH730N-and-WH-CH530) says only that the WH-1000XM4C 'will be available in Black and Platinum Silver this fall'; retail coverage narrows it to September 2026 with deliveries quoted September 23 - October 1. Dated to the last day of the stated month, September 30, 2026, as an estimate.
Sony's[1] own press release confirms it introduced the WH-1000XM4C headphones, with a 10-band EQ, on 7 September 2026 - one day before the pin's stored 8 September 2026 date, consistent with a roundup compiled shortly after.
Engadget's own headline and 7 September 2026 publish date report Sony[1] reviving the WH-1000XM4 as a refreshed $300 headphone option, closely matching the pin's stored 8 September 2026 date, though the page itself could not be fetched to quote directly.
What Hi-Fi?'s launch news says "The biggest change is to the battery" to meet EU regulation (EU) 2023/1542, and that "the 40mm driver of the original carries over to XM4C, as does the DSEE Extreme processing engine and the HD Noise Cancelling Processor QN1".
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