I currently use a Garmin 660. I also use a Sena 20S intercom. The 20S can, concurrently, do a A2DP media connection to a phone (Android Samsung S7) and an HFP connection to the Garmin 660. But... there is no volume control for the 660 in BT mode. That means the voice prompts, etc. come blasting into the headset. Drop the 20S' volume to the point where the 660's volume is usable and the phone is now almost inaudible.
I managed something of a workaround by finding a music app that can be really loud, so I can drop the 20S' volume and make the 660 sound usable. But this is all a collection of workarounds.
Does the Rider 550 have a direct BT volume control?
Best answer by RBEmerson
Um... have you updated your 20S to firmware V2.0 (present rev. from Sena)? How carefully have you read the TomTom manual for the 550? How carefully did you read the manual for the 20S?
With firmware V2.0 installed, among other features, the 20S supports two A2DP (full, music grade connections, with volume control supported).
First, follow the pairing instructions on p.21 of the 550 owner's manual. Be very careful to follow the sequence of pairings.
Step one is to pair the phone (your phone's owner's manual or how-to's about Android pairing) to the 20S (P.19 of the 20S OM), and 5500 (p.22 of the 550 OM). Step 2 is to tie the 550 to the phone (p.22 of the 550 OM). Step 3 is to tie the 550 (p.22 of the 550 OM) to the 20S (p.20, section 5.2 of the 20S OM). Select A2DP, do not select HFP on the 550, switch HFP off.
How to manage volume isn't not (or at least not obvious) in the 550 OM. The process is easy. Turn off the 20S. Get to the map screen (normal operation). Tap the mini settings icon in the upper left corner. Set the volume down to about 40-50% (or lower). Turn on the 20S and let it connect to the phone and 550 (could take up to a minute).
To test the volume setting, go to main menu, scroll to Settings, enter and go to Voices. Click on the name of the current voice to get it to announce what it does. The sound will appear on the 20S' headset (speakers or headphones). Play some music and test the voice again. The music will fade while Samantha (or the voice of your choice) speaks at a volume that's easy to live with.
This project isn't too hard. Just be very careful to follow the instructions.