Part of the new epos M12i product description. Read on . . . . .
"The M12i uses the revised Epos 25mm (1 in.) low distortion metal dome tweeter, designed to have smooth, clear and extended treble. Featuring a strong die-cast aluminium alloy face plate, moulded surround, ferrite magnet and Ferrofluid cooling, it is a significant improvement over the earlier M tweeter. The upper frequency crossover is centred on 5kHz and the minimalistic 1st order crossover is simply a polypropylene film capacitor."