Did you know you can connect the Fire TV audio to BT headphones or speakers? I recently paired a minijambox BT speaker to a bedroom Fire TV (mostly for music listening to use instead of the TV speakers if I want to, or to transport the speaker playing music from Fire TV to other nearby rooms.
Here's the story from Amazon, (funny, they only talk about connecting headphones but not speakers, but what's the difference? Nothing!)
https://www.amazon.com/gp/help/customer/display.html?nodeId=201739920