According to rtings.com blog they didn't notice an audible change from 2B584, and didn't have a test done on that version - they do, however, show a degradation in low frequency ANC with the change from 2B588 to 2C54. So, they say 2B588 is better.
Hi rtings, They’ve been many reports on Apple’s forums (https://discussions.apple.com/thread/250887615) and on reddit (https://www.reddit.com/r/airpods/comments/ebjadh/new_firmware_released_for_gen2_and_pro_models/) that the first and second firmwar
www.rtings.com
I still don't see why those of us on 2C54 are stuck while they leave hundreds of thousands keep using 2B588.
Mind you, my ANC is still very good for the fan next to my bed or exercise bike, bedroom ceiling fan, running water, the clothes washer and dryer, fireplace fan or the stove fan. But, it's really irritating to use in my car as a passenger trying to rest and hearing all the bass come through the APP.