Home Studio Practitioner
Microphone polar patterns are something that is mostly overlooked by a modern home studio practitioner, so we offer tips for using the polar patterns of your microphones to your advantage.
by Luka Sraka, Sept 2016
Microphone Polar Patterns 101
We are all familiar with words such as cardioid, omnidirectional and figure eight, but what do these words mean?
A polar pattern, even though it is represented as a two dimensional figure on the side of microphones or on the microphone manual sheet, is a three dimensional pattern that show us how a microphone (from which sides) picks up the sound. The omnidirectional polar pattern on a piece of paper looks like a circle but is actually a sphere.
There are two fundamental microphone patterns: omnidirectional, which picks up the sound all around the microphone capsule, and figure eight pattern, which picks up the sound in front and from the back of the microphone but not on the sides. All the other polar patterns are combinations of the fundamental two. The fundamental polar patterns are the result of different microphone capsule design. The omnidirectional capsule is a pressure-operated element and the capsule that provides the figure eight pattern is a pressure-gradient element.
Whereas first cardioid microphones were built using these two elements combined, most of the modern cardioid microphones use one capsule which is housed in its casing in a way that manipulates the phase of sounds reaching the back capsule to produce the desired cardioid pattern.
Most of the entry level condenser microphones have a fixed polar pattern that is cardioid. The more expensive ones have a switch with which you can choose a polar pattern. Some of them have the three most common options, omnidirectional cardioid and figure eight and some have the option to choose a setting anywhere in between those three settings. Ribbon microphones for example have also a fixed polar pattern, in this case a figure eight.
Forgetting about the technical aspects, here are some tips and tricks as to how you can use the different polar patterns to your advantage when recording.
The first thing that comes to mind is directionality of a microphone, or in other words from which sides the microphone picks up the sound. Different polar patterns mean that the sound is picked up by a microphone in a different way. When a microphone is set to omnidirectional polar pattern the microphone picks up the sound everywhere around the capsule. The figure eight means that the microphone picks up sound in front and in the back but rejects the sound from the sides and the cardioid polar pattern (the shape of a heart) picks the most of the sound in front of the microphone, some of the sound from the sides and none from behind the microphone.
We can use the directionality of microphone in recording to help us achieve the desired effects. If we are dealing with fixed polar pattern microphones we can use the knowledge of polar pattern in our advantage to position the microphone correctly so it picks up the sounds that we want and rejects the sounds that we don’t want.
I wrote about how to position a cardioid microphone to reject any unwanted noises in the first home studio practitioner article. Since cardioid polar pattern picks up sound in front of the capsule and not behind, we can position the microphone so it captures what we want to hear (for example a singer) and reject the sound coming from behind (room reflections or other instruments).
If we use a figure eight polar pattern microphone such as a ribbon mic which is typically used for recording guitars we have to acknowledge that it will pick sound waves in front and from the back of the capsule, but will reject the sound from the sides. We have to position the mic in a way that the microphone sides are facing the things we do not want to hear.
Mid-Side (MS) Microphone Technique
As you can imagine polar patterns can be used for different recording techniques as well, mid-side or MS recording technique is one of them.
MS recoding is a mean of coincident stereo recording, while XY recording is the most used method, the MS recording sounds more complex and offers some advantages over standard coincident (XY) miking.
As with any stereo rig, you need two microphones (unless you have a stereo microphone), one has to be set in cardioid (it can also be omnidirectional) and the other in figure eight polar pattern. The microphones have to be set very close together, usually one above the other and they have to be perpendicular. The microphone facing the instrument has to be set in cardioid polar pattern and the one which side is facing the instrument has to be set to figure eight polar pattern.
You can now start recording, but the process is not yet finished. When you have the takes you want in our DAW duplicate the track with the figure eight microphone (make a new track and copy the recorded material to it). Reverse the polarity of one of the figure eight tracks, pan them hard left and right and behold the sonic magic. In essence the two tracks of the figure eight microphones now represent the left and right side of the microphone. Changing the polarity of one of the tracks means that instead of cancelling out when panned hard left and right, we now hear the left and the right side from the microphone. Increase the volume of the two figure eight tracks for a wider sonic image and decrease the volume for a more focused image.
Frequency Response and Proximity Effects
Another thing to consider is the different frequency responses from different polar patterns. In a way it is a polar pattern tone control.
Cardioid and figure eight polar patterns have the most proximity effect. The closer to the capsule you go, more of the bass frequencies it will pick up. The figure eight microphone is useful if we cannot get the microphone up close to the source (if for example the singer is also playing a guitar). The bigger proximity effect of the figure eight polar pattern will help us retain the perfect sound even from a distance.
Using an omnidirectional setting can be good for immediate direct sounds since the pattern doesn’t produce a lot of proximity effect, we can get the microphone right up close to the source and capture it without the bass boost we would get by using cardioid or figure eight polar patterns.