Unfortunately, I'm not blown away by the P9. I made the mistake of not trying before buying and made the choice of buying based on the majority of positive opinions and reviews, purely coz demo units weren't available for me to audition.
I've done my listening tests with iPhone 6 Plus, iRiver Clix (aka U10 in some parts of the world), and HTC 10. Didn't bother with dedicated external amps coz this HP is meant for portable use and introducing an amp in my opinion hinders the entire concept and convenience of portability.
Don't get me wrong, the P9 is awesome. It's almost jewelry and a thing of beauty and exceptional quality. I do not regret buying it, but to me it's not worth twice as much as a P7. For an example, the jump from a P5 to a P7 in SQ was quite substantial IMO for not that much of a substantial price hike in comparison to the price hike from a P7 to a P9. The price hike from a P7 to a P9 does not necessarily reflect the same level of sound quality improvements that the P7 brought over the P5 IMO, unfortunately.
To me, P9 = P7 + bigger/heavier cans + slightly more comfortable to wear + slightly better mids + slightly more detailed highs and slightly better channel separation which results in slightly better sound stage. But the price is not "Slightly" more. it's considerably more. In fact, it's more than twice as much here in Aus (P7 RRP is AUD $499, P9 is AUD $1399).
As usual, the build quality, attention to detail and material quality is impeccable of the headphones. For the money that they make us part with for this set, B&W honestly could have done a better job with the cable IMHO. But overall it's probably the best built over ear HPs I've ever owned, followed closely by the P7 and Beyerdynamic T1. Awesome levels of sub bass as well, when the track calls for it of course. Re: Sub bass: The iPhone seems to roll of sub bass quite a lot, so it's almost non-existent. Not the case with the iriver or htc 10
The bass/sub bass doesn't drown out the rest of the sound spectrum either, which is impressive
Oh, and yes, it leaks sound. At very comfortable listening levels (between 40 - 50% volume with an iPhone 6 plus), if you are in a quiet room (eg:library), ppl sitting very close to you (within a couple of feet) may hear what you are listening to. If you are in public transport or other generally noisy environments, ppl will still hear music, but they may not be able to clearly make out what your are listening to. If you are listening to music around 50% in an iPhone 6 plus, you will not notice general background noise or others conversing, unless it's loud like a door slam or your loved ones or friends at work speak out louder, trying to get your attention.
There is no DAC (lightning to 3.5mm) in the box for the iPhone 7/7+. The manual clearly states the this headset is designed for ios devices, and mentions every ios device bar the iPhone 7 and 7 plus. The DAC is supposed to be available in the box from next year. For those of us who have already bought it, B&W is meant to ship one to us in 2017 via the local distributors (according to the re-seller that i purchased from) if you have registered the product via the B&W website.
Again and finally, if you have lots of cash, and want nothing but the best B&W headphones, then the P9's are for you. But if you are looking for value for $$$, the P7 or the P7 wireless are an absolute bargain. I honestly believe the P7/P7 wireless are 80-90% already there in SQ, for less than 50% the price tag.
Hope this helps your buying decision
