Proximity effect

Directional mics measure the pressure difference between the front and back of the diaphragm. At close range that difference grows faster at low frequencies than at high ones, so the bass can climb by well over ten decibels as the distance shrinks to a few centimetres. Pure pressure mics — omnis — have no proximity effect at all. It is strongest in figure-8 designs, which means ribbons.

Radio presenters and crooners have used it for nearly a century to sound larger than life, and singers who "work the mic" move in and out to shape their tone. For everyone else it's mostly a nuisance, which is why many mics carry a low-cut switch. An EQ handles the rest.