Loudspeaker amplifiers
Modern solid state audio amplifiers do not use matched impedances, contrary to myth. The driver amplifier has a low output impedance, such as < 0.1 ohm, and the loudspeaker usually has an input impedance of 4, 8, or 16 ohms, which is many times larger than the former. This type of connection is impedance bridging, and it provides better damping of the loudspeaker cone to minimize distortion.
Of course this is from wikipedia so who knows. It does have the ring of truth to it though. You may also want to read the LM386 datasheet and app notes.

"The myth comes from tube audio amplifiers, which required impedance matching for proper, reliable operation. Most of these had output transformer taps to approximately match the amplifier output to typical loudspeaker impedances."