The impedance describes the electrical resistance of the speaker. This resistance depends on the frequency of the reproduced music signal. Since frequencies between approx. 20 and 20,000 Hz are transmitted when the speaker is in operation, and the impedance also fluctuates.
The note "4-8 ohms" indicates that the minimum impedance is approx. 4 ohms and the maximum impedance is approx. 8 ohms. In our experience, you can operate Teufel speakers with all currently available receivers and amplifiers without any problems.