early Pipedreams used round planar drivers. Then Pioneer horn loaded ribbons were used. Finally the domes were used though they are custom and can't be used as singles. All worked very well and many of the chages were for practical as well as sonic reasons. The new Scaena speakers use planar tweeters and were designed by many of the Pipedreams designers. The use of many drivers to reduce the effort of any single driver is the affect that was desired.