The 18Sound 18LW1400, Eminence Delta Pro 18 and the Void 18-1000. Other drivers have been mentioned but yet need to be confirmed.
The 18LW1400 and V18-1000 have both been measured in the 3th prototype, the current release however is the 5th protype, the 4th being Cubo 15. The 18LW1400 measured a higher sensitivty then Cubo 15 over the <100 Hz range, crossover around 80 or 90 Hz sounded best.
The V18-1000 haa a tremendous kick. Hearing the kickdrum from an amplified drumset crossed at 125 Hz puts a smile on my face every time.
The Delta Pro is owned by a forummember.
Best regards
Cubo