metalman posted: Harald, try pairing the Zumo to the Sena with "mobile phone pairing". Music from the Zumo should sound good again. Then pair the phone to the Sena with "phone selective paring". Should work for calls OK. Music from the phone will probably be poor quality. I think this will get you what you're looking for.
Try adjusting the volume of each device when each device is transmitting, i.e., you're on a phone call or when the Zumo is playing your music. Hope this helps.
This is the way I understand it should go, too.
BUT, when I try to connect my Zumo 660LM with "mobile phone pairing" the Zumo says, "Passkey is 1234," and there's no way to enter a passcode on the Sena.
Now, that's with the Zumo attempting to pair as a "Phone". The Zumo can also attempt to pair as "Audio". (These options are available on the Settings-Bluetooth page, along with Bluetooth Enabled/Disabled and Friendly Name.)
First I cleared out all Bluetooth connections on all three devices: GPS, phone, Sena.
I've connected with Zumo as "Phone" and -- separately -- as "Audio", with these combinations:
1) Sena in "Mobile Phone Pairing", (Sena manual, section 5.1),
2) Sena in "Bluetooth GPS Navigation Pairing", (section 5.4, HFP only), and,
3) Sena in "A2DP Stereo Music Only", (section 6.1).
None of those combinations get me music from the Zumo. I know the music is playing, because the counter is counting up and headphones directly to the Zumo have music.
This is driving me NUTS. I get so frustrated with devices that don't behave how I want them to.