Just unbeliveable, ceramic cones, domes which are only 0.4mm or 0.2mm thick. Though we know that the transient response (rise time) has nothing to do with the speaker mass, we can still benefit from this light but rigid structure. In fact the plus of this speaker units is beyond imagination. One should hear the details in high frequencies in order to believe. I know from full-range drivers that it is very hard to keep the balance while trying to deliver much detail as possible. Despite the tweeter holds the energy much longer and returns to its' rest position much later than any other tweeter, it is yet amazing that it can perform this beautifully. This is in fact another phenomenon which needs to be explained in physico-acoustics.

The speaker units were matched together with an active cross-over. The cross-over is a 2nd order Linkwitz-Riley with a cut-off frequency at 2.2Khz. 4 Class A solid state amplifiers, which can deliver 10Watts (RMS, under 8ohm static load) were used to drive the speaker units. Operating tempature is 55 degrees Celcius under 25 degrees Celcius room tempature. Delay circuits were used for tweeters. There are two notch filters in the audiable frequency band. 

The enclosures were made from 8mm thick Aluminum. Total systems weights over 50Kg.