Randy,
The original M80ti was tested by Soundstage magazine at the National Research Council's anechoic chamber in August, 2001, and those frequency response and impedance curves are still available on the Soundstage speaker measurements site.
The M80ti's crossover was redesigned in the summer of 2003. All subsequent M80s had the new crossover, which resulted in smoother frequency response across much of the speaker's bandwidth. The new M80, which we later designated the "v2", was tested in December 2005 and you can see the improvements in the smoother "listening window" frequency response curves on the Soundstage site.
The impedance curve for the M80v2 on the Soundstage site is the correct curve for the M80s after the crossover was changed in the summer of 2003, even though we did not incorporate the "v2" into the model name until later on. The curve is different from the earlier M80ti impedance curve, because the crossover of the M80v2 is a new crossover design with different values of components.
Impedance curves do not reflect the acoustic frequency response of a loudspeaker. It shows only how the electrical resistance (impedance) of the driver voice coils and crossover components vary with frequency.
Regards,
