While the Elac Debut B6 has a specified nominal impedance of 6 ohms, it can be seen in Stereophile’s measurements that its impedance is above 10 ohms at all frequencies above 500 Hz, and is above 20 ohms at almost all frequencies above 1 kHz! 6 ohms in this case is its minimum value at any frequency, which it reaches at 10 Hz (the lowest frequency they measure, which of course is not too far from the 0 Hz frequency at which your multimeter measurement was taken), and also around 200 Hz.
IMO most manufacturers would have specified the nominal impedance of that speaker as being much higher than 6 ohms. Certainly at least 8 ohms, and perhaps 10 or 12 ohms or even more.
Many variables affect the impedance of a speaker, and how that impedance may differ from what it is at DC, including the drivers, the crossover networks, the enclosure, and how the designer chooses to specify the impedance. I would ignore the 15 to 20% rules of thumb you mentioned reading about.
Regards,
-- Al
IMO most manufacturers would have specified the nominal impedance of that speaker as being much higher than 6 ohms. Certainly at least 8 ohms, and perhaps 10 or 12 ohms or even more.
Many variables affect the impedance of a speaker, and how that impedance may differ from what it is at DC, including the drivers, the crossover networks, the enclosure, and how the designer chooses to specify the impedance. I would ignore the 15 to 20% rules of thumb you mentioned reading about.
Regards,
-- Al