Thank you for suggestion trellus, but the intention of the wireless and the buttons is you can controlling this (volume) and other aspects directly from the headphones and not from the device. Unfortunately (for me) I changing the volume very frequently and using the iPhone or mbp directly always for this is very, very inconvenient. I know this aspect can changing with firmware update because bowers & wilkins doing this very soon after the releasing of the p7 wireless 3,5 years ago.
Another trick I use is to my Apple Watch to change volume of iPhone to my Bluetooth headphones, using the digital crown, which also gives fine-grained control, and it's very convenient, just as or frankly more convenient than the headphone volume control, which is often far more clunkier than the digital crown on the Apple Watch. Just another suggestion.
