Feb 16, 2020
@joelirwin Thanks for advising. Here spent half one day to research and downgrade the firmware to 3.1.8 eventually. Looks like this version provide ANC better performance indeed and i do a test while smoke ventilator is working in kitchen. Noise cancelling distinguish apparently rather than ver.4.5.2 and meet my demands finally.
Feb 17, 2020
Created an account to add my two cents. Headphones are basically useless at this point.
I've cleared the bluetooth device list and even reset the headphones with no joy.
My serial number ends in AE - date of manufacturing was December 2017.
Oct 25, 2019
Mine had the first two issues you had. I got so tired of it so I filed for a warranty replacement (mine were still in the 1 year warranty). The serial for mine ended in AZ, produced sometime in late 2018 I think.
My new replacement pair arrived yesterday with 4.3.6 installed and the ANC is back to what I expected.
New owner of QC35 II with AZ serial number and part time QC35 firmware researcher here. (I could write a whole book about it by now!)
Small recap about QC35 II firmware versions (after having read all 222+ pages in this thread and many other sources as well)
2.1.3 is the lowest you can go with AZ hardware (2.0.1 only works on AE serial number)
2.2.1 may have the best ANC performance of all firmware versions (according to several reports from 2018 complaining about sudden ANC degradation after installing 2.5.1)
2.5.1 first time ANC got destroyed, however there's also reports about this version having the best ANC performance
3.1.8 seems to offer the best "overall package" (ANC performance vs. bluetooth bug fixes)
4.1.3 is the oldest firmware QC35 II with AZ serial number was ever shipped with from factory and is technically the same as 3.1.8 according to Bose (which is plausible considering the exact same release date). I went with 3.1.8 non the less as there's a few people arguing that "all 4.x.x versions" suffer from bad ANC performance.
Please be aware that switching between high/low ANC strength on the QC35 doesn't change the microphone gains but rather completely switches the external microphones on/off
ANC high means that both external and internal microphones are used for picking up noise to feed the ANC algorithm, giving the best ANC performance but picking wind noise up as well.
ANC low means that only the internal microphones are used for ANC, greatly diminishing the ANC effect but eliminiating the wind noise problem.
There appears to be a bug in firmware 4.5.2 with the external microphone gains, causing the high setting to be only slightly better than low setting. If your QC35 II with 4.5.2 firmware don't pick up any major wind noise on high setting you're affected by it.
So after 3 weeks of getting accustomed to the stock 4.3.6 firmware I eventually downgraded to 3.1.8 in the middle of a 3 hour long noisy car ride to better assess if there's any ANC difference at all.
My immediate observation was a slightly stronger cabin pressure feeling - as if a "hole" in the ANC frequency spectrum has suddently been patched, further amplifying the cabin pressure effect. To be honest the difference isn't mind blowing at all and people who have a strong initial sensitivity to cabin pressure may actually be better off with the 4.3.6 firmware.
It's important to remember that cabin pressure is a pure psychosomatic effect due to sensoric dissonances (similar to motion/sea sickness) that normally fades away the longer the brain is exposed to it (building up tolerance), however a manufacturer (Bose) cannot expect any scientific understanding from the ordinary customer and thus has to strike a compromise between a good ANC performance and the problematic cabin pressure feeling that comes along with it. A more agressive ANC needs longer adjustment time and could pose a problem as customers may be scared off by its effect in the first place, not buying the product at all or immediately returning it, unaware of the concept of tolerance. Bose has acknowledged this by implementing 10 different microphone gain settings in their new NC700 headphones.
Feb 19, 2020
After the firmware upgrade to 4.5.2 the ANC had been worse and after several contacts with Bose Support the Headphones were exchanged, having now still the older version of firmware.
The Bose Connect App always reminds me to install the latest firmware, not mentioning the version.
Does anybody know, whether meanwhile (after more than 6 month of this known issue) Bose has a newer Firmware available? Which is the version?
I want to avoid that my replaced Headphones will be „destroyed“ by 4.5.2. again.
I was told Bose understood the problem and is working on a new version....
Jan 8, 2020
Really excellent Post! Thanks for this great summary and explanation👍
I've AE-ending serial number - manufactured in July 2018 - and downgraded from 3.1.8 to 2.5.1 before doing a trip to Asia.
I can say that on a noisy turbo-prop plane, the ANC under 2.5.1 was very good...couldn't hear any background/external noise. Imo the 2 series offers better ANC than 3. Here's a summary of each version:
After downgrading, I did feel there was more internal 'pressure'; can now understand why this then takes a bit of time to adjust to and that there's no absolute "best-for-everyone"
Bought a pair of QC35ii from Saturn in Hamburg not knowing about the underlying software issues. Anyway, at first they felt sooo good - noise cancellation at its best. I think the manufacturing date was in 2017. Following an update (I wasn’t really paying attention to firmware versions) they started popping, clicking and just making a loud noise on the left side. So I decided to have them exchanged. About 10 days later (which was yesterday) I received a new pair. As I put them on, all I hear is a constant hiss when the ANC is on. In fact, in a fairly quiet room you can hear proper hissing from the unit. It’s so frustrating that hey didn’t even bother checking the new unit before sending it out. So I am returning this pair today. It’s pathetic, I feel I should have never bought them in the first place. This is supposedly a premium set of earphones costing hundreds of euros.
No offense but your post would be incredibly more useful if you could at least be bothered to state serial number (AE/AZ) and firmware versions of each headphone mentioned.
Going by your ambiguous description it is unclear if just a (probably) newer firmware or the (likely) AZ hardware of your newer (replaced) headphones introduced white noise that wasn't present (at all?) with AE serial / (unknown) firmware before.
There's a good number of reports about increased white noise in later firmware versions although I haven't come across a single QC35 unit that doesn't employ any white noise at all and given the physics behind ANC I find it very unlikely that those units ever existed in the first place.
Sorry man, I am just a user - thank you for being aware of all that could be wrong and sharing. It's disheartening that an end-product behaves like a test-product. Yes, the second set was AZ serial, the first wasn't. With the first set I could hear the silence itself, it was so good, whereas with the AZ I could hear filtered noise, straight out of the box. In a quiet room there was more noise with the headphones on than having them off - I mean, is this a joke or what...
Funny thing is, with the first set, the non-AZ one, I remember upgrading to the latest firmware (2 weeks ago) and there was no filtered noise afterwards. However, during my return flight I was getting a loud popping sound coming from the left headphone.
Anyway, I've posted the second unit back and honestly had enough of testing corporate products while they launder my money.
P.S. will update on the case
Nov 8, 2019
hey @Wayne_M ,
it's been a month -- how about that "more detailed update"? How's the progress of the analysis of the affected headsets? Have you learned something?
Original message from wayne_M: