I have been told this is not generally a good idea, as it runs the current "through" the first speaker (and all its drivers, internal wiring, and crossover) to get to the second speaker.
Most Home Audio speakers are not designed for this, and they will not sound as good.
While series wiring is common knowledge it is more associated with the wiring of drivers in a multiple driver single speaker, not multiple speaker applications where quality sound is the goal.
Pro speakers used in speaker banks and speakers of that type "are" designed for using multiple speakers.
So I would check with your speaker manufacturer before wiring your speakers that way.
Even this little paragraph says it is not often a good idea SERIES