Microphone polar patterns explained: Lobar

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You may have heard of polar patterns, but wonder what it was. So, what is a polar pattern? A polar pattern is a description of the directional sensitivity of a microphone to sound pressure. In other words, the polar pattern of a microphone indicates in which direction(s) the microphone will be more sensitive to picking up sound and in which direction(s) a microphone will reject sound.

A microphone’s polar pattern is a way to display its directional sensitivity. There are some microphones with fixed patterns, while others can switch between quite several different patterns.

Polar patterns are also known as the microphones’ pick-up pattern. The pattern of the microphone shows how well the microphone will responds or pickup sound, depending on the angle from which the sound is coming. The best response angle of a microphone is known as the on-axis response. While the other angles are called off-axis.

The specifications of the polar pattern of a microphone are specified qualitatively and quantitatively in the technical data or specification sheets of the microphone.

What is the Lobar polar pattern?

lobar pattern img

Of all the known standard polar pattern for microphones, the Lobar polar pattern is probably the most fascinating.

The Lobar pattern is a unidirectional pattern, which means it is more sensitive in one direction. This is indicated at 0° on-axis in the graph of its polar response.

However, that’s not all there is to it. The Lobar polar pattern has three other additional sensitivity lobes: one on each side (90° and 270°) and one at the back (180°). Though the lobes are less sensitive, they are however almost as narrow/directional like the main on-axis pickup.

A “weapon” that doesn’t shoot

Although the Lobar pattern is fascinating, it is above all, more theoretical. Most shotgun microphones have the front and rear lobes, however, only a small fraction of them is likely to have the side lobes of the “real” Lobar pattern.

The shotgun polar pattern is generally made from the super-cardioid or hyper-cardioid capsule, but it can only be achievable using a long interference tube that is fixed in front of the capsule.
The microphone has a long-slotted interference tube that works as an acoustic labyrinth right in front of the microphone capsule. The sound that is sent directly on-axis passes through the tube without an issue.

The sounds entering the tube from an off-angle do not find it so easy. There are slots in the tube which are designed in a way to phase-cancel different sound waves at different frequencies as the sounds move along the tube.

This reduces the pattern of pickup of an already directional super-cardioid or hyper-cardioid capsule, thereby turning it into a Lobar or a shotgun polar pattern.

The angle of acceptance of a shotgun microphone polar pattern quite depends on the length of the tube and some other design factors, this also includes the design of the microphone capsule itself.

When Should You Use A Lobar/Shotgun Microphone?

Shotgun microphones are often thought of as specialized or specialty microphones. While they excel in some situations, they are not even considered in many other applications. So, in this section, we will discuss in what condition or application it is best to utilize a shotgun or Lobar microphones, as well as those where it is not advisable to use these types of microphones.

Shotgun microphones are largely used and popular among filmmakers, but they are rarely used in the studios. These special microphones are mostly praised in their niche and are completely ignored in others. The other areas where Lobar or shotgun microphones are best applied are;

  • For the recording of a narrow-angle of audio.
  • Best to record directional sounds remotely without the fear of of-axis sounds filtering in.

Pros of the shotgun Lobar polar pattern

  • Good for recording wildlife, etc. because they have a high off-axis suppression or rejection
  • They can focus on a relatively small area that’s usually quite a distance from the microphone
  • Quite a several sound men have reported having used this kind of microphones for sound in video shoots and have also testified that the effect is quite pronounced when you listen to the sound through headphones
  • Using this microphone will produce excellent results if you are in a reverberant or very noisy room. This is the reason these types of microphones are used for live TV or talk shows

Cons of using the shotgun or Lobar polar pattern

  • Very limited application (e.g. long distance, isolated recordings)
  • In live sound reinforcement, it has to be used directly in front of foldback monitors
  • Whenever it is to be used, you have to conceal the microphone.

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