Importance of impedance graphs?

[sweetliberty]

Why do some contributers place so much importance of speaker impedance graphs? Apart from the obvious demand placed on amps. Can anyone please explain this?

[Zilch]

1) Impedance controls the frequency response of passive filter elements used with the driver.

2) The impedance curve indicates the resonance frequencies of the driver and/or system, fundamental and anomalous.

3) The T/S parameters of the driver may be computed from the measured impedance behavior.

4) Impedance defines the electrical load "seen" by the amplifier.

5) More that hasn't come to mind yet.... ;)

[moldyoldy]

And that "the obvious demand placed on amps" isn't a trivial thing when one considers that power requirements double for each loss of 3 of those innocent little dB marks on a response plot, which is largely controlled by...the impedance characteristic. :)