I have a hands free, Bury 9600 CC, and a Lumia 800.
I have the same problem with Bluetooth, Nokia Drive and getting the voice over the car speaker.
On the Bury 9600 CC I found an option to turn on/off A2DP,(see below).
When turning it off I got voice guidance from the phone speaker, and could still use the phone with hands free.
But then I couldn't use the Bury 9600 CC for controlling the Music Hub on the phone.
Turning A2DP on again, I can control the Music Hub, use hands free but no voice guidance from phone speaker or car speaker.
So here I see a part of the problem/solution.
And when we get the WP7.8 update Nokia updates Bluetooth transfer of DRM. (Again see below, the last 2 lines)
Will this update bring good or bad news for the hands free or will it not do anything at all?
Does Nokia know that it could be in the A2DP/DRM connections that the problem is?
And will Nokia solve this problem now that we know other WP-brands can use handsfree GPS/navigation?
Advanced Audio Distribution Profile (A2DP)
This profile defines how high quality audio (stereo or mono) can be streamed from one device to another over a Bluetooth connection. For example, music can be streamed from a mobile phone, to a wireless headset, hearing aid & cochlear implant streamer, car audio, or from a laptop/desktop to a wireless headset.
A2DP was initially used in conjunction with an intermediate Bluetooth transceiver that connects to a standard audio output jack, encodes the incoming audio to a Bluetooth-friendly format, and sends the signal wirelessly to Bluetooth headphones that decode and play the audio. Bluetooth headphones, especially the more advanced models, often come with a microphone and support for the Headset (HSP),Hands-Free (HFP) and Audio/Video Remote Control (AVRCP) profiles.
A2DP is designed to transfer a uni-directional 2-channel stereo audio stream, like music from an MP3 player, to a headset or car radio.This profile relies on AVDTP and GAVDP. It includes mandatory support for the low-complexity SBC codec (not to be confused with Bluetooth's voice-signal codecs such as CVSDM), and supports optionally: MPEG-1, MPEG-2, MPEG-4, AAC, and ATRAC, and is extensible to support manufacturer-defined codecs, such as apt-X. Some Bluetooth stacks enforce the SCMS-T digital rights management (DRM) scheme. In these cases, it is impossible to connect certain A2DP headphones for high quality audio.