Scanspeak 18M/4631T00 18 cm Revelator midrange drive unit.
This new addition to the ground breaking Revelator series of dedicated midrange drivers features a larger 18cm sliced / glued pulp cone and a rigid titanium voice coil former. The low loss suspension and coated foam surround help this lovely unit yield a very useful sensitivity of 92 dB whilst still producing excellent midrange clarity and upper range extension. Highly recommended.
A full datasheet can be downloaded from this page.