These microboxes are my personal smallest portable system. Derived from two Empire M2 set, using only passive boxes to allocate the little contacts plate with a mini-reflex port just drilled into plastic. A separated power supply mini-amp 3 W RMS x 2 drives these mini speakers rated in frequency range from 200 Hz. 2\" magnesium-alu diaphragm, vented coil Omnes Audio BB 2.01 - competition hi-fi car midranges - rated of 10 W RMS into 4 Ohm. Just incredible at listening to.