Cardioid Mic : What is it? Everything you need to know

This is one of the most used microphones in home recording studio settings, no question about it. Despite also called "unidirectional mics", they don't completely cancel noises picked up outside the range of the capsule. Any sounds coming from a source 90 degrees outside the axis are reduced in around 6dB. That translates into two times the distance of any sound coming from the front of the mic. But, sounds sent 180 degrees from the pick up angle of the cardioid mic will seem as if they were ten times farther away. It is estimated that it reduces in 67% any sound coming from the outside of the pick up range of this pattern. Know everything about this kind of microphone and understand the best ways to use it.

When to use a cardioid mic

Cardioid microphones are ideal for stage and close-mic settings, since they block leaks and undesired sounds. In recordings, you can use unidirectional mics in many situations. For example:

• Amplifiers: Cardioid microphones positioned facing the speaker - it can be a guitar, a keyboard or even a bass amp. Besides keeping leaks and room noises away, it picks up the characteristic sound of the instrument through the amplifier, combining that with any of the functions that the device may have: equalizer, pre-amp, valves or transistors. You might prefer that as an alternative to record in line, direct on the mixing board.
• Live in studio: Some bands might like to keep the energy of the live performance in their studio recordings as well. The cardioid mic is the perfect tool for that kind of production. Avoiding leaks of one instrument into another. For example: the microphone of the singer will pick up much less volume from the acoustic guitar played by him or her. That makes all the difference in the editing, equalizing and mixing of your final recording.
• Drums: The cardioid mic allows the isolated "miking" of a single drum of the whole kit. In post-production, to have all the tracks of each drum separated (with sufficiently low leaks), helps quite a lot for mixing as well.

Aesthetic tips

When recording drums we must pay attention to some important details such as style and taste of the player. Every drummer has their own set up and the placing of the microphones on it has to fit that drum kit. It must follow the taste of the artist too. One way to do it is to put individual microphones on each drum: one on each tom, one or two on the snare, one for hi-hat and one on the bass drum. Cymbals are usually miked with two microphones above it - the overheads. In other situations, you can use one microphone placed on the snare, another on the bass drum and the two overheads to pick up the whole kit. There are many configurations possible to record drums, in which the cardioid mic might be of great help. In some cases you can even use a cardioid and a omnidirectional or a figure 8 microphone combined. A great technique for vocals or piano, for instance.

Pick up patterns

Keep in mind that the description of cardioid is related to the polar pattern of the microphone only. Because the sensitive part of the capsule is shaped like a heart. So, a cardioid microphone can also be a condenser microphone or a dynamic microphone. Let's explain that. Any microphone has a set of characteristics that define its use, range and pick up qualities. The most important ones are:

• Transducer mechanism (dynamic, condenser or ribbon);
• Type of amplification of the circuit (valves or transistors);
• Polar pattern (cardioid, omnidirectional, figure 8, shotgun, super cardioid);

In other words, the polar pattern is directionality. Or the area captured by the microphone.

Omnidirectional and bidirectional (figure 8)

Initially there were only omnidirectional or bidirectional microphones (figure 8).

• Omnidirectional: picks up sound equally around its capsule;
• Bidirectional (figure 8): picks up sound equally from the front and the rear. Canceling sounds from either side. Ribbon microphones will always have this pattern, because of the physic limitations of the ribbon's construction (the ribbon side has almost no picking up area, only the face of the mic). The space that is sensible to picking up sound has a shape similar to the format of the number 8, that's why it can also be called figure 8.

Cardioid mic

Over the years, audio engineers have been combining omnidirectional with bidirectional patterns. That technique eventually led to the development of the cardioid mic.

This is how it works: if the sound source is in the back of the microphone, the negative signal of the bidirectional cancels the positive signal of the omnidirectional. But if the sound source is coming from the front of the mic, positive signals of both types are combined. As a result the pick up range gets even stronger.

The developing of that model, in many forms originated more specific ones.

Speaking of unidirectional microphones, one important aspect is the movement of the sound source. Singers for example, tend to move quite a lot on stage or when holding the mic in studio. Using a cardioid mic can cause significant impact on the final result of your work. And enables you to control the excess of movement of the vocalist. It is very important to try and find the perfect position in order to record the voice properly.

Super and hyper cardioid mic

To be able to make cardioid microphones even more directional, developers created the super cardioid mic and the hyper cardioid mic. With these types of microphones the picking up area got more reduced, avoiding sounds created outside the capsule axis.

However, both super and hyper cardioid have a tiny pick up spot on the back side, that allows some small leaks on 180 degrees of the front side.

Shotgun

You can also find another variation of a cardioid mic called shotgun. It is shaped like the weapon it got named after, this microphone obtains high gain picking up sound from long distances. More concentrated on the axis of the capsule, it is a very directional microphone. Picking up sound mainly from where it is pointed at. The shotgun mic is highly used in video clip sets and film shooting; TV broadcasting and lectures in auditoriums and concert halls. This microphones attenuate almost any sound coming from the outside of its picking up area.

Multi-pattern

It is currently available on the market the multi-pattern microphone. This type combines two cardioid capsules, so the user can choose which type of pattern to use:

• When activating the two cardioid signs it becomes omnidirectional;
• If reversing the polarity, it is now a figure 8;
• But if cancelling one of the signs, you'll get a cardioid;

Keep in mind that multi-pattern microphones can be all those patters or not! For example, there are some manufacturers that give one of two options only.

Cardioid mic vs. Omnidirectional mic

After all the explanation it's easier to know in which cases to utilize each type of microphone, right? But it's always good to remember that the application of each type also has to do with the aesthetic choices of the project. It will always depend on what you intent to reach sound-wise.

• Cardioid microphone: Dry pickup, with less ambience and no reverb. You can add more gain to it, because it cancels outside noises well. Easier to work with its results in post-production, once the sound would be a lot cleaner and with almost no ambience. It can be use with lead vocals, acoustic guitar, guitar amplifier, horns and drums.
• Omnidirectional microphone: It has flat frequency response and is more sensitive to the proximity of the sound source. Picks up a lot of room and react well to "p", "b" and "t" sounds of vocals, as well as mechanic noises. Great for drum overheads, on pianos, choirs, string quartets and orchestras.

More aesthetic tips

Something we frequently see is the combination of both types together. A cardioid mic on each instrument and omnidirectional microphones in strategic places of the room, picking up ambience and the energy of live performance. You can do that to record drums. Positioning one microphone on each drum, two overheads and one omnidirectional microphone in front of the drum kit, a few meters away. As a result, you will get a clean sound of each drum and a cool room sound.

Most common cardioid mics

• Shure SM58: one of the most popular microphones in the world of audio. The dynamic capsule makes it perfect for live shows and recordings. From vocals, horns and brass to drums and guitar amps. It can take strong sound pressure. It has long durability and great cost-benefit.

• Audio-Technica AT2020: Highly chosen among other condensers of cardioid pattern. It has wide frequency response and low noise pickup. Recommended for home studios and live recordings.

Whatever style you will end up developing as a studio tech or sound engineer, be sure cardioid microphones will be part of it and cannot be left out of your list of must-have equipment. They are a great option for anytime.