Cardioid, Omni, Figure-8 – Why Do Microphones Have Different Pickup Patterns?
Our ears can do a lot of things: We can simply hear what’s going on, or we can listen very closely. And sometimes we just don’t want to hear about it. Microphones can do similar things!
Let’s say you’re at a party, and there’s music playing and people talking. You enter the room, taking in the whole scene. You listen to the music playing in the background while everybody’s talking, you might even secretly overhear a conversation where your name got mentioned, while you’re saying hello to a friend. It’s pretty amazing what we can do with just one set of ears! But then again, we have a powerful signal processor between our ears! Simply put, microphones come with different pickup patterns for the lack of a brain.
Omnidirectional microphones are microphones that hear everything that’s going on around them. They are equally sensitive to sound from all directions. This would be the equivalent of us humans “taking in the whole scene.” Omnidirectional microphones are often used for orchestra recordings. But they can also be very useful in the home studio; for instance, when you record acoustic guitar, percussion, or background vocals, or anything that sounds best with some room ambience.
Cardioid or Unidirectional
A cardioid microphone doesn’t just hear, it listens. In technical terms, a cardioid microphone is most sensitive to sound coming from the front. Sound from the sides is picked up somewhat quieter, and sound from the rear is greatly rejected. That’s exactly what we want, most of the time, which is why the great majority of stage and studio microphones come with a cardioid pattern. Cardioid microphones are great for recoding vocals and anything that’s supposed to sound “dry” and “close”.
Figure-8 or Bidirectional
This is a somewhat weird way of listening which would be very hard to do for a human. It is the equivalent of listening to two guys standing on either side of you while ignoring everything else. A microphone with a Figure-8 or bidirectional pickup pattern is sensitive to sound coming from the front and coming from the rear, but has a very high rejection for sound coming from the sides. This may not appear very useful to you, at first. But there are a lot of interesting “advanced” applications for figure-8 microphones such as mid/side and Blumlein stereo techniques. Figure-8 happens to be the natural pattern of ribbon microphones, and most multipattern condensers can be set to figure-8. Other than that, figure-8 microphones are pretty rare. There are hardly any figure-8 moving coil microphones, and only a handful of manufacturers (including Neumann) offer “true” figure-8 small diaphragm condenser microphones. (“True” in this context means, the capsule achieves its figure-8 patternwith only one diaphragm).
Apart from the major patterns omni, cardioid, and figure-8, there are some varieties of the cardioid pattern, the best known being wide cardioid and super- or hypercardiod. Wide cardioid is a mix of omni and cardioid, i.e. a less directional form of cardioid. Wide cardioid is excellent for recording acoustic guitar and small vocal groups.
Super- and hypercardioid are patterns in-between cardioid and figure-8, i.e. they are even more focused on sound from the front, but sound from the rear isn’t suppressed quite as much. Their maximum cancellation is somewhat left and right to the rear, in an angle of about 110-125 degrees to the front. This can be useful in live situations. Hypercardioid microphones are also great for drums, e.g. when you want to record the snare with as little spill from the hi-hat as possible.
Pickup Patterns and the Proximity Effect
The directionality of a microphone also has an effect on the so called proximity effect, i.e. an increase in bass response as you move closer to the mic. The proximity effect is what makes the DJ on the radio sound like Barry White. But it can also diminish intelligibility and can lead to unwanted bass build-up with voices and instruments getting in the way of bass instruments. The proximity effect is strongest on figure-8 microphones, and still pretty strong (though somewhat less) on cardioids. Omnidirectional microphones don’t have any proximity effect at all.