Unfortunately, the volume control on my iPhone 6 Plus is unsatisfactory. The smallest possible volume, which can be set corresponds to the fourth smallest in the iPhone. Since the headset has a very high efficiency, so it is me too loud in quiet surroundings.
If, on the iPhone, a lower volume, beeps of Airy and mute. Increasing the volume again, you can hear again what.
On an Android phone, the problem does not occur.
Did the devil Support angemailt and awaiting response. At the same time I ordered a similar headphones from AKG and test this once it is there.
*** Supplement 12.11.2014: A AKG Y45BT shows exactly the same behavior. So there seems to be due to the BT-implementation of the iPhone.