I seem to remember reading about this phenomenon with omni mics before somewhere a long time ago,
but I just took the opportunity to record a noisy vent in one of my rooms and I recorded it with an MK5 mic set in cardioid, and then I recorded it in omni, with no change of position of the mic.
The cardioid mic had an average level of -52.9 dB and a peak of -38.8 dB.
The omni mic had an average of -35.5 dB and a peak of -21.5 dB.
Nothing changed on the preamp level or position of the mic, only the polar pattern.
But it sounds like there is a whole lot more sub-bass and rumble on the omni, and the level is boosted quite a bit (which, I can understand that the whole room as opposed to the front of the mic is being recorded, but the sub-bass baffles me).
Do I have a defective mic or does an omni pattern pick up a lot more sub-bass and rumble, and how come I didn't know about this before? Is this known about or written anywhere?
Could I use this to an advantage for recording guns, for instance?