Thanks for posting in the community!
You can certainly stream Amazon music to both speakers in sync. You would want to make sure the first speaker that starts the group has the strongest Wi-Fi signal. To check, go to the SoundTouch app and select settings. From here, scroll to "About" and then select the speaker. Whichever has the strongest RSSI value will be the one I recommend you start off with. If you have any other questions, don't hesitate to ask!
Tony - Community Support
Jun 27, 2018
I will be able to stream same station from Amazon Music on the 10 and 20? And they gonna move togther without lagging at one and not the other??
I mean if there is a lag or problem in amazon servers do they both lag or maybe one?
The answer is "sometimes"
You will have better luck with pairing the 20 to the 10, not 10 to 20. But still it will not last. You should read the Discussion
"UPDATED JUNE 12th - MASTER: Play All not working correctly after 19.x update"
Pinned at the start of the SoundTouch Speakers section. This discusses all the problems people are having with "pairing" "grouping" and "play all", etc.