She also needs to be very aware of the limited range of Bluetooth. About 30 feet, line-of-sight is it. A wall in the way can significantly reduce the range of Bluetooth. Some people are shocked by how poor the range of Bluetooth is. This is why wired is so much better and why audio devices which sit on a home network (like Sonos) are often so much better. The range of Wi-Fi can be much further than what Bluetooth allows for.
This is just something to be aware of.
But, yes, the Onkyo needs to use the Zone 2 output, or a Record Out connection or something similar to allow for a Bluetooth transmitter to be connected to it and allow playback elsewhere.
30 feet is only for older versions- BT 4.0 and newer have significantly better range. I have posted about the Miccus BT piece that I used for a school gym audio upgrade and until that morning, My opinion, based on experience was "BT sucks!". The gym teacher was there and asked why I didn't want to use BT and I gave him my opinion on the distance, but he said "I have an amplifier that works over 100 feet". I told him that I would like to see it and off we went, to see that it actually worked well over that distance.
I went home, looked online for new info and found that BT5.0 was current, what's different and definitely better, checked for options and ordered one, all before 11:30AM. It arrived at 7:30 that evening and I immediately connected it to my garage receiver, linked my iPhone and started streaming. I listened, decided that it sounded decent and started to walk away, waiting for it to lose connection where the $300 Musical Fidelity piece (of crap) failed and it didn't drop out. I kept walking and it never lost connection, even after I walked to the end of my 105' driveway. I kept walking and even across the street, it worked. I stopped walking when I was about 150' away and my brick house was between me and the BT receiver.
At the school, it covers a full-sized basketball court plus the 15' border and passes through two concrete block walls. I haven't received a single trouble call about it since it was installed in early September, 2018.
It has analog and optical in and can be used as a transmitter or receiver. Also, the antennae can be removed and relocated for better range by using an SMA cable with the appropriate ends, available online for about ten bucks each.
The BT receiver cost about fifty dollars and when I needed to cancel the announcement when connecting and disconnecting, tech support actually answered quickly and told me how to do it without putting me on hold- they just knew it.
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