When iPhones are connected to the bluetooth on Fisker Karma, changing of volume is disabled. YOu CANNOT change volume from your handset during a phone call. This is the same for most cars. it's an Apple implementation.
This is only possible with Android, Blackberry, Windows, and all other phones.
One trick you can try is, when the iPhone is NOT connected to the Karma, place a call and change the volume during that call to about medium level. Then when the phone is reconnected to the Karma's bluetooth, it will hopefully stay around that setting.
The reason this lower volume trick works is, the karma's bluetooth system will perform automatic gain control (ACG) of all outgoing sounds (from the mic) and incoming sounds (to the speaker system).
During the latest software revision, a huge improvement and change was done to re-tune the entire echo cancelation + automatic gain control algorithm. If you guys remember one of the earlier softwares had almost no echo cancelation algorithm so the person on the other side can hear very clearly their own voice.
However, because the way the algorithm is written, it had a negative consequence to the ACG.
how the crackling sound happens:
When Karma's phone system detects incoming sound from the other side during a phone call, it will always attempt to adjust the level to the user's setting (whatever your volume setting is). But during a pause in the conversation, it thinks the sound is too quiet and maxes out the ACG gain. When the person on the other side speaks again, the sound is immediately distorted. However, you will notice if the person keeps speaking, the crackling will go away and the sound will be leveled to normal. Then it repeats when there's a pause again.
When you adjust the volume on your cell phone, you are basically lowering that "max level" so even when the ACG maxes out, it is still audible sound and not distorted.
