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Why are low impedance speakers harder to drive than high impedance speakers

I don't understand the electrical reason for this. I look at it from a mechanical point of view. If I have a spring that is of less resistance, and push it with my hand, it takes little effort, and I am not working hard to push it. When I have a stiffer spring (higher resistance)  I have to work harder to push it. This is inversely proportional when we are looking at amplifier/speaker values.

So, when I look at a speaker with an 8 ohm rating, it is easier to drive than a speaker with a 4 ohm load. This does not make sense to me, although I know it to be true. I have yet been able to have it explained to me that makes it clear.  Can someone explain this to me in a manner that does not require an EE degree?

Thanks

128x128crazyeddy
cymbop
315 posts
 
I've heard it described like this:  remember that the amp is not just pushing against a spring in one direction, but rather pushing and pulling back and forth.  Less impedance, e.g. a lighter spring in your analogy, means more slop, more wiggle room, that the amp must now cope with in order to control the woofer.

Almarg, please weigh in and set us all straight.  ;-)
randy-11
1,913 posts
 
It's about the amp.  Amps like to put out at 8 ohms.  The mechanical analogy isn't a good one.  Instead, think about your past gf's.
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cleeds
5,949 posts
 
A low impedance speaker requires greater current from the amplifier to result in the same voltage at the output.
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