An omnidirectional microphone has sensitivity at all angles – in principle picking up sound equally from all directions. This gives you extremely natural and realistic sound compared to a cardioid mic. Omni mics are often used for picking up ambient sounds, as well as miking a large sound source such as a choir in a recording situation Unfortunately, due to their pickup pattern, omnis can also produce a lot of feedback in live situations.
Nonetheless, we recommend that you try a DPA omni first because, when used close to the sound source, the equal frequency response makes these mics a flexible addition in your audio toolbox. It will often give a more natural sound, it can handle extremely high sound pressure levels, it does not suffer from proximity effect and is not as sensitive to wind, pop or handling noise.