I'm not certain that a lot of of the APM's design is that rational to begin with. The headband to cup attachment spring loaded pivot mechanism for example : I can't think of a lot of good reasons for it.
In the following patent, showing a part that looks very similar to the finished product's mechanism (figure 6 and on) : https://pdfaiw.uspto.gov/.aiw?PageNum=0&docid=20190238963&IDKey=A9D47CF727DC&HomeUrl=http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2%26Sect2=HITOFF%26u=%252Fnetahtml%252FPTO%252Fsearch-adv.html%26r=10%26p=1%26f=G%26l=50%26d=PG01%26S1=(apple.AANM.%2BAND%2B20190801.PD.)%26OS=aanm/apple%2Band%2Bpd/8/1/2019%26RS=(AANM/apple%2BAND%2BPD/20190801)
They justify it by writing this :
So the theoretical benefits would be that by eliminating the traditional yoke mechanism the spring loaded pivot could reduce the overall bulk of the headphones.
That's very theoretical because :
- As the XM4 shows a traditional yoke design can still result in a headband with a low profile and not stick out too much from the head (counter examples : HD350BT, H95, these make you look like Teletubbies). You just have to offset the yoke.
- Other headphones can also achieve a slim earcup profile (Huawei FreeBuds Studio for example).
- The total weight of the APM is among the highest in its class - and I'm ready to bet that the pivot mechanism alone is significantly heavier than ugly, cheap but still reliable plastic Y shaped yokes.
- The width and height of the cups is among the largest in its class (some of it is just because there's a lot of empty air in them though. When apple introduced the Macbook 12" they said they don't want to ship air, well that's very much what they're doing with the APM
).And the drawbacks are significant :
- It might be one of the most - if not the most - complicated mechanical piece ever put in a pair of headphones : https://www.ifixit.com/Teardown/AirPods+Max+Teardown/139369
One of the reasons I got to use several copies of it is that a few of them would develop a mechanical "click" in that area after a while.
It must have been a nightmare to solve from a production / tolerancing perspective and probably adds quite a bit to the cost.
As a general rule the APM's design requires (often needlessly as simpler solutions were available) super-tight tolerances to even work, but the pivot particularly so.
- More importantly it severely compromises the capacity of the APM to properly seal in edge cases. The beauty of a well-designed (I'm afraid most aren't), traditional yoke mechanism is that "it just works" in the sense that it naturally applies the clamping force of the headband in the right area on the earcup, allowing the latter's range of motion to evenly compress the pads around the ear with no need for a spring or a complicated mechanism. With Apple's solution you have two forces fighting against each others : the headband's clamping force, applying pressure at the top of the cups, and the spring loaded mechanism, applying pressure at the bottom. Since this is fixed at the design stage, it results in a sub-optimal pad compression for everyone as we all have a different head shape (some people will have too much pressure at the top, others at the bottom for example). While my ex Bose 700 would consistently seal regardless of how much I bended my neck, with the AirPods Max seal gets broken when I significantly rotate it (although it's nowhere near as bad as the K371, another example of a poor hinge design). The only way I found to improve that problem is to forcefully bend the headband outwards to reduce clamp pressure - thereby alterating the ratio between these two contradicting forces in a way that suits my head shape better. Thankfully the feedback mechanism maintains a more or less constant FR curve regardless of that design as long as I'm not hitting edge situations.
I'm actually very impressed that Apple made that irrational design decision decently work for most people (I'm still getting a decent seal most of the time), but I can't even imagine the amount of resources that must have been wasted in it for very few benefits in the end to the user.
As ugly as it is, the QC35II (and most likely the upcoming QC45) is for me a much simpler way to make a design that flat-out works better in nearly every way as portable, ANC over-ears (comfort, consistency of seal, packability, ease of deployment, etc.).
Apple has a history of taking some rather weird decisions that may not be that rational to begin with. The AirPods Pro's flush venting hole for example, for which Apple took the rather unusual (for them) step to make an explicit hardware revision (now it's slightly recessed, to reduce its chance of it getting clogged up with ear wax and result in this : https://support.apple.com/en-us/HT211147.
When you look at he previous revision you just go "why did they not think of that :/ ?"
Sound-wise, I encourage you to actually try them.
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