I think the big secret is the ATC midrange unit, the SM75-150S. It is one of the most linear drivers I have seen and heard - and it covers almost the ENTIRE vocal range. There is no break in the middle from crossing over to another speaker. IMHO you cannot underestimate this fact. BTW - if you are concerned about shelling out the incredible dough for the ATC 50s and you are a bit handy (or know someone who is), there is Wilmslow Audio in the UK (wilmslow-audio.co.uk) who sell an identical (ATC approved) kit that costs less than half of the ready-made version (about 3200 Pounds for the active pair, if I remember correctly). Again, the quality of the midrange unit is unquestioned, it is truly one of the best drivers on the market, period. Sorry, TransaudioGroup - didn't mean to take business away from you...
