I really believe its the way some people pronounce words with the 6666 stock mic and possibly the way it is made. I myself cut and stuck a large thick foam mic windscreen to the front of both mics but the 6666 still had this weird muffly sound to it. Its also weird how they built it inside as it looks like the mic element is actually below the rounded section inside where you would normally talk into where the element usually is in other mics. The DNC520 now sounds great like a studio mic almost and no background noise that was there before the foam. The DNC520 was also louder than the stock on my talkback when hooked up first without the foam.