I would like to start a thread for seldom seen, odd and rare speakers. I have owned some throughout my years in the audio hobby. I would like to start with my Dennesen 180 electrostatic's. The tweeters were engineered with Arthur JansZen and Frank Dennesen for the Electrostatic ERC 139 Speaker. Frank Dennesen ended up using this tweeter for many years afterwards in his designs. The 180's use an 8" alnico woofer that has been doped and used some reticulated foam as an early phase plug seen on woofers today. I hope others with rare odd speakers to join in.