Re: Bose QC 35 ii firmware 4.5.2
I also applyed the firmware 4.5.2 on my QC35II. As I had the headphone on ears while it was updating - after having listened to music for about an hour - I immediately noticed white noice in background when that was finished. Firstable I have believed ANC was disabled, but no.
I have also felt the ANC was little more poor and I couldn't ear no more any difference between high and low level.
I took the plane few days after for a 10 hours travel, and I must say the headphones were however still appreciables. I could observe a real difference between high/low/off ANC. I have thought that the ANC was re-tuned especially for aircraft engine noise and low frequencies in general, and less reduction for vocals.
As I had contacted Bose technical service to expose my problem after upgrade, they had proposed me to return back my headphone for an exchange. So I accepted, because I wanted to recover my previous experience
I have received the new one with firmware 4.1.3. But this one has a white noise too, and I would say it's even more audible. From memory the ANC is not neither better nor worst.
I have found a solution to downgrade it to 3.1.8 on reddit.com and re-tested the headphone after. Still some white noise but lower, the ANC seems little better. But when listening to music I hear by moments poor audio quality with kind of saturation on basses or like if the decoding looses quality. It also was the case on my previous headphone, before the upgrade, and I don't remember having this problem again after.
So I decided to finally upgrade again to 4.5.2 (cause now, I know how to return back to previous firmware if necessary) and I must say I now don't feel any differences, but music quality seems more stable. I need to test longer to be sure of that.
For the 3.1.8 as for the 4.5.2, I have tested the ANC with the TV on (for human voices) and with an aircraft cabin noise on the hifi speakers (sorry for the neighbours).
What I can say is that the ANC performance depends a lot of the heaphone placement over the ears. In my case, the best is when it is a little in rear. That may align the ear canals with the speakers and so with the noise cancellation waves. Another important point is that the pads must entirely close the ear all around, any leak is source of external noise. The respect or not of these two points change significantly the noise reduction. I wasn't paying attention for that previously.
By reading others comments, it seems there is no solution for white noise. Even for those who returned back to their previous firmware, the noise remained. But it is inaudible when music plays.
Hope my experience can help.