Has anyone ever plotted the tweeters upper frequency response limit? My RTA measurements reveal a useable response to at least 20k but that is the instruments highest measureable band and judging by how effortlessly it makes it there, it seems reasonable that it can go yet further up. According to JBL publications, a -10 db point is claimed between 6k5 and 21k5 but at which end, low,high or both? My guess is the lower end.