Frequence response conveys the breadth of tones that the headphone drivers are able to produce, from the lowest bass notes to the highest treble frequencies. The human ear can usually hear a range from 20Hz up to 20,000Hz (or 20kHz), so a pair of headphones that at least covers this range is a must for video editing. Most boast an even wider response range though, which at the low/bass end can be beneficial, because while you may not be able to hear these frequencies, it is possible to feel them.