The impedance is the Resistance, which consists of the components capacitor, Kitchen sink and ohmic resistance is formed and whose value and phase position changes with the frequency.
The DC resistance says nothing about how the amplifier in the audible frequency range.
For example:
A capacitor of 100 microfarads at different frequencies: DC voltage: infinite (however finite in practice, but very high, the higher the quality the capacitor)
10Hz: 159 Ohm
100Hz 15,9ohms
1.000Hz 1,59ohms
10.000Hz 0,159ohms
according to the formula: Impedance = 1 / (2 times Pi times frequency times capacity)
In the crossover of an LS, several coils, capacitors and resistors are usually connected criss-cross, in addition to the voice coils of the Chassis, which is why the impedance of a speaker is the easiest to measure.
Cable Impedance:
A cable also has an impedance. It can be divided into capacitors: the two wires next to each other and coils: the wires themselves are part of a large diameter coil. The impedance can be changed by clumsily laying long LS cables (wound up in a ring).
impedance at Cinch-Cable:
Signals are influenced via cables. Due to the cable impedance, what is sent out at the source no longer reaches the receiver exactly. Output stages should have low impedance, input stages should have higher impedance. Depending on the ratio of the two values, the impedance of the cable no longer plays a role. A 2 m long cinch cable can usually be neglected. In the case of 20 m long cables, it may be that the impedance of the cable and the interference radiation play a role.
Summary of various statements about speaker impedance:
A lot of new ones Loudspeakers with the indication "8 ohms" and all Loudspeakers with the indication "4-8 Ohm" are according to investigations
completely normal 4-ohm speakers and therefore just as critical or uncritical in an 8-ohm amplifier as a Loudspeakers with the specification "4 ohms". But by that Loudspeakers with the "8-ohm" specification are in fact only 4-ohm speakers, the Efficiency doubled the real value in promotional papers!
For loudspeakers with the specification "impedance 4 ohms" one should be able to assume that this is usually the standardized one
"Nominal Impedance" (with a minimum allowable of 3,2 ohms) is meant. The only exceptions to this are a few high-end loudspeakers and Loudspeakers American origin. These can sometimes even fall below the 2 ohm mark.