dunno the NTK - BUT the C4000 is definitely harsh sounding, man. I have a pair - I use them as a second choice - meaning, when I run out of mics.. NEVER got them right for overheads. Only on accordion or upright bass - because for the moment I don't have another LDD for that.
For the price, C4000 are good enough, but maybe you should save more money and get somethin' in the upper league - Soundelux coes to mind - or even Groove Tubes.
Or Shure SM7b - if you're into rock vocals, or Electrovoice RE 20 if you want it for kik or floor toms also, or barss instruments.