Rauliruegas...It happens that I have a spectrum analyser in my system, and can therefore give sure answers about frequency response.
The Maggie 1.6 low end rolls off rapidly around 40 Hz, which is exactly what Magneplanar says. For most music their low end sounds better than you would expect because it is very smooth, and the planar format means that SPL is quite uniform throughout the room (at least in my room).
My SW systems exhibit flat SPL to 1250 Hz. (And they are flat to 20 Hz). This is when driving them with a full range white noise signal. However, if you drive them with a swept-frequency tone, distortion becomes evident around 400 Hz. So the SPL is there at 1000Hz, but some of it is harmonic distortion.
Advocates of small drivers may find it hard to believe that a 15" driver can do 400 Hz or higher. Actually it is not the size (mass) of the cone that matters, but rather the ratio of the motor power to the cone mass. My 15" driver has a 4" voice coil, and about 20 pounds of magnet, driven by 600 watts, so it is not at all surprising that it can perform well up to 400 Hz. I also have a set of JBL LE15A drivers (used in some of their classic top-of-the-line systems) and they are good for 800Hz (but they won't do much below 30 Hz).
About the 200 to 300 Hz crossover...this is just for certain types of music, most notably theatre organ, but also brass bands and massed choral music. There is no way that three MG1.6 can deliver the impact of six big cones.
