When using a GPS with “mono Bluetooth audio” (like a Zumo 550) as a main audio source for music with a Bluetooth communication system or intercom, you will not have quality stereo sound. The GPS must have the A2DP Bluetooth profile in order to get stereo sound in the Bluetooth headset.
If your GPS does not have the A2DP Bluetooth profile, the guys at Interphone have a solution for you. You will need the Interphone Dual 3.5mm Stereo Bluetooth Transmitter.
The chart below demonstrates the setup step by step.Use your back button to exit.