Try this paste of a PM I received from a fellow forum dweller as we both worked through some stuff for Iron Butt rallies. We've got four of them between us and five FJRs. It applies to your case...mostly. Key differences in your case being no MP3 player and you gotta buy an SM10 and assuming an audio box for the V1. I would note the Sena 20S is WAY better than an SMH-10 was for this kind of advanced connectivity. The PM is about 3 1/2 years old, but I found WELL WORTH wading through as I found what he said to be 100% correct and the terms he used are very specific (i.e. "phone selective paring", "media selective pairing"). By the end of a 3 day stretch I had my audio setup actually working the way I wanted it!
Also can confirm the BT module for the the V1. Very disappointing.....but it is what it is.
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I spent a bit of time playing with my audio setup tonight. I think we have the same priorities, but they might be slightly different depending upon how you want the phone to work. My favored setup at the moment is:
Valentine 1 <-> Remote Audio Adapter <-> SM10 Aux Port
iPhone 6+ < Bluetooth > Zumo 590 < Audio Out Jack > SM10 Music Port
iPhone 6+ < Bluetooth > Sena 20S
SM10 < Bluetooth > Sena 20S
I'm using media selective pairing to pair the 20S with the SM10 and phone selective pairing to pair the 20S with the iPhone. On the Zumo 590, I select Media and Apps but leave Phone deselected on the bluetooth settings.
This gives me Radar, except for during phone conversations. It does work during intercom conversations using the audio multitasking feature of the 20S. With the SMH10, you'd lose radar audio in during intercom conversations in addition to during phone calls.
iPhone audio comes through and GPS voice instructions interrupt the iPhone audio. The one thing that doesn't work here that I'd like is if the Zumo paused the iPhone audio during a voice instruction and then un-paused it when the voice instruction was done. The Zumo media controls work to play/pause select audio from the iPhone.
By pairing the phone to the 20S using phone selective pairing, I'm trading off the ability to dial and see incoming caller id on the Zumo for the ability to use Siri. For me, the iPhone is mounted on the bars and lights up when someone calls so I'm good with this. I've also read a lot of complaints about call audio quality using a Zumo in the middle of the phone and headset. I'm not sure how many of these applied to the 590 vs. other devices since I'm not that interested in the calling features of the device.
The one spot that this setup seems to be weird lies in the USB port on the 590. I haven't completely narrowed down what the cause is but the 590 has the ability to perform media functions on an iPhone or iPod using the USB port. If the iPhone gets connected this way, the SmartLink features won't work because they only work over bluetooth. Unplugging the iPhone for a second to allow it to connect over bluetooth and then plugging the charger back in seems to remove the issue but to completely solve it, I'll probably just not use the charging port on the 590.
I think this configuration gives you everything that you were looking for. If you pick up a 20S, you'll gain the ability to hear all of the audio routed through the SM10 during intercom conversations in addition to ambient noise mode. Other than that, the SMH10 works about the same.
If you find a better configuration, I'd be interested in hearing about it.
-Erik