Impulse Response indicates the speed and accuracy of a microphone to reproduce fast transients (such as in percussion). A microphone with good impulse response will reproduce the attack very quickly and accurately (the leading edge of the waveform goes nearly straight up). A microphone with slower impulse response will not reproduce transients accurately (the leading edge of the waveform rises slower). In such instances an attack will sound will not be as crisp and may sound smeared.
Unlike conventional microphones, Earthworks microphones exhibit fast rise time, fast recovery time, fast diaphragm settling time with no unwanted ringing or reflections.