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What is unidirectional microphone capsule? Three things to learn

Of all the components as well as design that go right into developing a microphone, the capsule is the most important aspect. Unidirectional microphone capsule is the component accountable for the conversion of audio waves right into mic signals. It includes diaphragm(s) as well as the housing. In this article, we will go further into the inner workings of mic capsules.

How does a cardioid capsule work - Two elements matter

As we all know, microphone works as a transducer to transform sound waves into mic signals or electrical power. Specifically speaking, it is the mic capsule that actually comes into play. And there are two important parts that you need to learn about it.

Firstly, you can watch the video to know how a directional microphone for camera performs in audio pickup.

This video is a review of the SYNCO D2, a shotgun directional microphone at SYNCO, created by the YouTuber TLDR Filmmaker. He compared the audio pickup between omnidirectional lav mic and unidirectional D2 in the video from 2:37. You can jump to that part to feel the difference intuitively.

SYNCO D2 directional microphone is sold at Moman PhotoGears Store

Go and buy SYNCO D2 at Moman PhotoGears Store


Unidirectional microphone capsule diaphragmA microphone diaphragm is a thin film that moves in response to changes in sound pressure (sound waves). It is a key component in an electret mic capsule. Without a movable diaphragm, a microphone would certainly not be able to do its work as a transducer. The synchronizing activity of the diaphragm with audio stress is the very first action in transforming acoustic power right into electric power.

Given that a microphone diaphragm is so slim, we observe it as having just 2 sides. The motion of the diaphragm is based on the distinction in audio stress between its 2 sides.

Mic level & line level

The mic level stands for the voltage that a camera microphone etc. produces when it picks up sound, usually just a few thousandths of a volt. This voltage varies with sound level and distance. Microphone level is the weakest and requires a preamp to boost it to line level. It is typically specified between -60 and -40 dBu.

A line-level signal is about 1 volt or about 1,000 times that of a mic-level signal, so the two usually don't use the same input. This signal goes from your preamp to the amp that powers the speakers.

There are two standard line levels:

  • -10 dBV for consumer devices such as MP3 and DVD players
  • +4 dBu for professional equipment

Anatomy of unidirectional microphone capsule

The composition of a microphone capsule depends on the kind of microphone in inquiry. As a whole, there are 2 main transducer kinds:

  • Condenser microphone: It features a capacitor-like capsule and is usually signified as being either small-diaphragm or large-diaphragm.
  • Dynamic microphone: It consists of moving-coil mic (with a durable moving-coil capsule) and also ribbon mic.

Condenser microphone capsules

SYNCO V10 microphone Use mic with small diaphragm condenser capsule is used for camera recording.

Condenser microphone capsule gains popularity among engineers, musicians, and audiophiles. It transduces power through electrostatic concepts. A fundamental one is made as a round parallel-plate capacitor.

The 2 essential elements of any kind of electret condenser mic capsule are the movable diaphragm (front plate) and also the fixed backplate. A tensioning ring is integrated right into the housing as well as holds the slim diaphragm in place while supplying the correct stress on the diaphragm. There is a chamber inside the housing with suitable space between the parallel plates. At last, in order to extract the microphone signal, electrodes are connected to the diaphragm and backplate.

Large VS small diaphragm condenser microphone capsule

You may usually see large or small diaphragm when searching for condenser microphone. What’s the difference? LDCs, or large-diaphragm condensers usually have a diaphragm size of 1 inch (25.4 mm) or better. On the other hand, SDCs usually have a diaphragm size of 1/2 ″ (12.7 mm) or much less.

What concerning the unidirectional microphone capsule with diaphragm sizes in the range from 1/2’’ to 1’’? Throughout the background of microphones, embedded style methods have actually made it to make sure that there aren't numerous outliers within this variety. For the mics that do discover themselves in no guy's land, if the size is close to 1’’, it is normally like an LDC or an SDC if the size closer to 1/2’’.

Moving-coil dynamic microphone capsules

Like condenser mics, moving-coil dynamic mic also has capsule inside, which features circular diaphragms. Since it is in the type of dynamic, dynamic microphone cartridge works on different principle, the principle of electromagnetism. That is, it uses electromagnetic induction to transform energy.

So what is in the high quality electret microphone capsule? Usually talking, the "moving-coil" of conductive wire is affixed to the back side of the non-conductive diaphragm. The tensioning ring is utilized to make sure the diaphragm is tensioned appropriately and connected to the capsule housing.

The round conductive relocating coil is put on hold in a tiny void with magnets to its outside and also inside. The strange form of the magnet is attained with pole pieces. An electronics lead cable is connected to each end of the conductive coil.

How does this kind of unidirectional microphone capsule work? The moving coil will relocate when the diaphragm relocates according to acoustic wave. An AC voltage is created throughout the conductive coil using electro-magnetic induction when it oscillates within the electromagnetic field. Both lead wires take this AC voltage as the mic signal.

Pickup pattern - Feature that microphone capsule is responsible for

Shotgun mic capsule is key to the microphone's features and sound. For example, it is responsible for polar pattern. There are 3 basic types of microphone directionality:

  • Omnidirectional: The omni directional polar pattern has the same sensitivity to the sounds from any direction.
  • Bidirectional: Also known as figure-8 polar pattern, it gains the same sensitivity to the sounds from the front and rear while rejecting audio from the sides.
  • Unidirectional: It means that the mic is sensitive to the sounds from one direction. The most common one is cardioid.

As aforementioned, bidirectional and also omnidirectional each refers to a specific pickup pattern. Unidirectional microphone polar pattern is a wide term that describes all various other mic polar patterns (cardioid-type patterns and also even more).


So what is unidirectional microphone capsule? After reading the article, you can get the idea that it is the internal component of a microphone, which consists of diaphragm, backplate and the housing for diaphragm. It is also responsible for features like polar pattern, frequency response.