[bobthecabbage]

As I understand it high impedance speakers are easy to drive but not very loud and low impedance speakers are louder but harder to drive for a given power output. Reason being, low impedance speakers draw more current from the amp.

Now I'm not very good on speakers but in general terms if you put 4 ohms of resistance in parallel it averages out at 2ohms (and so will draw twice the current from the amp).