To ask what the best midrange driver is is even more difficult/impossible to answer as what is the best dome tweeter. There is no best. There are better, then it hits a point where the system has to be accounted for. Loudspeakers are *systems*. If you're gonna try an take a midrange driver to 5 or 6,000hz versus say 3 or 3.5--its gonna change your choices drastically. The higher you go the smaller your mid has to be if you don't want beaming. PHL makes some really nice midrange, but out of a 6.5" directivity suffers quite a bit above 3.5khz. When you say full range do you really mean FULL-RANGE 20hz to 20khz +/-3db. Is this going to be a three way design or a four way design, or maybe even a two way. If you want 115db dynamic range with low distortion from 20hz to 20khz you may be looking at a 4 way. This is also where you have to decide you design goals, aside from just full range. The Vifa P13 and P17 are classics. GR-research makes some nice ones for the money. The PHL's are nice as are some of the Scan-speaker units. I would say to at least avoid metal and ceramic coned units, if fidelity is the utmost importance.
