Connect electricity to a motor, it spins
Spin a motor, it becomes a generator and produces electricity
Put a load on the generator, it makes it difficult to spin
A speaker is a motor
Short the terminals, makes it difficult for the cone to move
And a dynamic driver, can be used as a passive radiator - albeit an inefficient one
But you really shouldn’t have any speakers in your room other than the ones your listening to…
Herb Reichert connects terminals on unused speakers in his review room. Also places them face to face when stored.