Steve Deckert

The response is +/ 3dB and this is standard for all speakers. Speakers are measured in an anechoic chamber with no reflections.
The nominal impedance is the impedance at each frequency between 20Hz and 20kHz averaged. Since the nominal impedance of a speaker might be said to be 8 ohms, yet a peak at resonance of 60 ohms, I don't see how it can be 80%. This is also true of all loudspeakers.
