Thanks!
Thank you to everyone who replied to my original post. I installed the dongle Friday evening, turned it on, and found out there was sound both in the headset and the speakers. Then I went away for the weekend (in the car, not on the Spyder). It was bothering me, but I didn't have the ability to work on it. I was in the garage today, playing with my toys, and I found that everything said in your replies is true. I was not aware that you could go into the menu and mute the external speakers. I tried that and found it to work well. I also tried lowering the volume on the external speakers, but not turning them off. That works equally well with the option of still using the speakers without having to go in the settings menu and turn them back on.
This has been an interesting journey. I started a few weeks ago, thinking that I would buy headsets so I could talk to my wife while we ride. And, while I'm at it, why not have the ability to listen to FM receivers built into the headsets. I shopped around for Sena 20s dual pack, bought from the lowest bidder (on eBay, but they have a great rating), and installed them. I instantly hated the FM radios built into the 20s headsets. The reception is poor and the sound is tinny. I realized that the Spyder has a far better radio built in, so I bought the Bluetooth dongle. The sound is far better than the 20s radio, but my wife and I will have to listen to the same radio station. She reminded me that we have been doing that for 34 years, so why stop now?
Again, thanks for your help. As always, you came through for the Spyder community with some great, and accurate, advice.