As far as I know, Alexa will only allow you to combine a single, non-Alexa specific Bluetooth speaker to say an Alexa dot. Also, you may have noticed, that when you do, the Alexa dot speaker disconnects but this allows you to use any of your Alexa devices in any part of the house to play music in a single room as long as the Bluetooth will reach. If you want stereo, you need to combine two Alexa specific devices together in the APP to form a left right stereo speaker pair. Now that isn't going to give you any type of real bass effects. I have an Alexa specific Bass Boom box using Wi-Fi. The Alexa app allows me to connect all three (actually two as the stereo pair appears as one device) together in a group. I added in another Alexa dot in that group and it connects to a Bluetooth speaker that I place in the background to get a fuller effect. Sound quality varies with which version of Alexa specific device you are using. The app limits what it will and will not allow you to connect together. PS: You may have to adjust lag times so one bluetooth speaker doesn't lag behind another.