I see many are concerned with the factor that the M2 ANC can't be turned off with BT mode on. I have been using these spectacular cans for several months, it has little sound leakage, a metal and leather construct, and an ANC which is modest but not sacrificing the sound quality, i do believe the Germans have designed them with some real effort. I would like to address some concerns mentioned above. I am sure these cans are for on-the-go use, the classy material speaks for itseff, so why turn off the ANC. I believe the dac inside the cans is carefullly calibrated with the ANC function, so turning it off gives you some lousy version of the built-in dac for sure, and with the ambient noise, it must have compromised the sound quality more than the ANC itself. Just plug in the wire if you are using it in some quiet environment., in this case i think ANC is barely operating to degrade your sound quality.
I tried using the iphone6s plus wired to the M2 directly (F.Y.I, interconnecting another external dac is never the on-the-go purpose) thus deactivating the ANC on my transit and the BT with ANC experience is superior. For people using the cans at home, just don't buy these cans, the extra cash for these cans are for the superior built in dac and the vintage design. My verdict is that it is a pair of on-the-go wireless headphone with great quality and wired to a nice dac at home, it gives you some nice experience if you want to add a pair of nice closed back headphone since your open backed headphones just keeps annoying your roommates.