It depends. If you connect the positive & negative terminals of both 4-Ohm speakers to the positive and negative terminals on the receiver, respectively, you are making a parallel connection and the total impedance would be 2-Ohms. However, if you connect the positive terminal of the 1st speaker to the positive terminal on the receiver, the negative of the 1st speaker to the positive of the 2nd, and the negative of the 2nd to the negative terminal on the receiver, you're connecting them in series and the total impedance would be 8-Ohms.
Does doing this really work? Thanks for all the help!