Willy Nilly and Millie Farad have a problem.  They have an AC source.  Here is the Thevenin equivalent.  The voltage is a music signal, and the internal resistance is 8 ohms.

        Willy and Millie want to get as much power as possible from the source, so they know they need an 8 ohm speaker.  Unfortunately, the speakers they have - when mesured - seem to be either 4 ohms or 16 ohms - half and twice the desired values.

• If the goal is maximum noise/sound power, which speaker should they use?
• How much "performance" do they lose using these speakers, and is it the same for both?

        For purposes of analysis, Willy and Millie agree that you could compare computations for V_o = 10v.