W4-657s

This driver doesn't go all the way up to 20kHz, but someone built a system with the 3" version (which will do 20kHz) and many people have a very good impression of TangBand drivers, especially for their low price. But you may want a fill tweeter for the highs if you use this driver. But this driver makes good midrange, and since most sound is midrange, if we can't get the midrange right, what's the point of extended low bass and super highs?

Use this driver and a Vifa Nd small-faceplate tweeter.