Activated dual audio bluetooth for 2 speakers

If you are asking about to line out signals into one or two stereo pair of speakers one typically uses a sound board to manage the inputs as the timing and volume of each source needs to be controlled.

If you want to have one output sent to a bunch of speakers, let's say an event so everyone can hear things that's the more common when using a phone as the music/voice source. This is a feature of the given speaker vendor, as an example UE speakers offer this via a phone App. Sadly it's limited to the given speakers App and Speakers.