This is a microphone to be reckoned with.
Most microphone manufacturers will tout their products on a subjective level with colorful adjectives such as airy, intimate, smooth, and warm; Earthworks' microphones are built for transparency. The QTC1's frequency response is ridiculously flat. According to the data sheet, typical accuracy from 20hz to 20khz is around ±0.5 dB. A quick glance at the frequency response graph will show that in fact, a similarly flat response can be had from this microphone from 4 hz to 40 khz, although both extremes of this value are well outside nearly every human's hearing range1. Earthworks currently sells these microphones for $2300 USD in a matched pair, or $1100 USD for a single mic. Similarly priced and even vastly more expensive microphones rarely come close to these levels of transparency and range of response.
QTC in the model number is an abbreviation for "quiet time coherent," referring to the extremely small amount of self noise the mic produces and the rapid speed at which the diaphragm is able to react to waveforms. The small size of the condensor capsule is probably responsible in part for the microphones excellent transient handling capabilites. The capsule is situated in the small, narrow end of the microphone, which upon first inspection mounted in the provided mic clip appears strangely reminiscent of a 1950s sci-fi raygun.
To sum up my personal experience with this particular microphone, I would have to say Earthworks' claims of transparency are true to the umpteenth degree. A stereo pair of QTC1s sound gorgeous in a piano, reproducing every nuance of the innards with incredible precision. The same is true with vocals, however, the result of a flat frequency response on anyone's voice is not altogether flattering. My reaction upon hearing my voice reproduced through the QTC1 in foldback was something to the effect of: "I really sound like that?" Infallible accuracy on a musical instrument is one thing, but most people's voices could use a little coloration. While this is a mic that strives for perfection, I doubt it will be putting the rest of the microphone industry out of business any time soon. Accuracy can be a bad thing.
Frequency response on axis: 4 Hz to 40 kHz ± 1 dB
Polar Pattern: Omnidirectional
Sensitivity: 30 mV/Pa (-30.5 dBV/Pa)
Power requirements: 48 V Phantom, 10 mA
Maximum acoustic input: 142 dB SPL with 5 kΩ load
Peak output voltage: 3 V into 1 kΩ, 10 V into 5 kΩ
Output: XLR intended to drive a balanced input
Minimum output load: 600 Ω between pins 2 and 3
Noise: 22 dB SPL (A weighted); 24.5 dB SPL (Unweighted)
Dimensions (L x D): 229 mm x 22 mm (9 x .860 inches)
Weight: 225 g (.5 lb)
1 If I were engineering a record for dogs, this would certainly be the mic of choice.