I have MG1.6, and a spectrum analyser to determine frequency response. The 1.6 does roll off the top 1/3 octave a few dB, which I can correct using an equalizer. Other than this top 1/3 octave the high end range is really flat, as per the Magneplanar specs. The owner's manual suggests that you may want to use the 1 ohm tweeter padding resistor (that they supply) to roll off the trebble. They say that a flat speaker may sound "hot" on the high end because recordings are often boosted on the high end to compensate for the rolled-off highs of many brands of speakers. With Maggies, the choice of tweeter padding resistor is left up to the user. Nice.
I would expect the Maggies which use the ribbon tweeter to be flat to, and above 20KHz as per the Magneplanar specs. However, they probably also need the resistor to sound flat with many commercial recordings.
I would expect the Maggies which use the ribbon tweeter to be flat to, and above 20KHz as per the Magneplanar specs. However, they probably also need the resistor to sound flat with many commercial recordings.