Among the tens of thousands of microphone designs out there, the cardioid polar pattern is the most popular. As an audio engineer, I use cardioid mics more than all other mic polar patterns combined.
What is a cardioid microphone? A cardioid microphone has a unidirectional cardioid polar/pick up pattern. It is most sensitive to on-axis sounds (where the mic “points”), generally 6 dB less sensitive to the sides, and has a null point to its rear. Cardioid mics are revered for their directionality and rejection of rear sounds.
The cardioid microphone polar pattern is also referred to as:
In this in-depth article, we’ll discuss the cardioid microphone polar pattern in great detail in order to answer any questions you may have about cardioid microphones!
This article focuses specifically on the cardioid microphone polar pattern. For an in-depth definition of microphone polar response along with descriptions of every mic polar pattern, check out my article The Complete Guide To Microphone Polar Patterns.
Table Of Contents
- The Cardioid Polar Pattern
- Cardioid Microphone Generalities
- How Is The Cardioid Polar Pattern Achieved?
- When Should You Use A Cardioid Microphone?
- List Of Miking Techniques With Cardioid Microphones
- Cardioid Microphone Examples
- All The Different Microphone Polar Patterns
- Cardioid-Type Polar Patterns
- Related Questions
The Cardioid Polar Pattern
A picture is worth a thousand words. Let’s start with a diagram of the cardioid microphone polar pattern:
Before we get into the description of the cardioid polar pattern, it’s critical to note that the above diagram is in 2-dimensions, though microphones actually work in 3-dimensions. In reality, the cardioid polar pattern looks more like this:
Let’s return to the original 2-D image for our explanation.
So in this diagram we imagine the cardioid microphone to be pointing upward (toward the 0° mark).
The graph shows multiple lines that represent angles around the microphone capsule in 2D (in increments of 30°). It also shows circles of sensitivity (in increments of 5 dB).
By studying the graph, we see the following:
- The cardioid polar pattern is the most sensitive on-axis at 0° (where the microphone points).
- The cardioid polar pattern is half as sensitive (-6 dB) to the sides at 90° and 270°.
- The cardioid pattern essentially has a hemispherical acceptance angle (based on the 180° spread between its two -6 dB points).
- The cardioid polar pattern has a null point of no sensitivity opposite to the direction it is pointing at 180°.
We call this pattern “cardioid,” “heart,” or “kidney” because of the way it looks on a 2D graph. The cardioid pattern and all other cardioid-type patterns are referred to as “unidirectional” because they are primarily sensitive in a single direction.
So what does this mean for cardioid microphones? How do they perform? Let’s look at some generalities.
Cardioid Microphone Generalities And Characteristics
- Most common mic pattern in studio, stage, and broadcasting.
- The standard unidirectional polar pattern.
- Null point at 180° (directly to the rear).
- Roughly 6 dB less sensitive at the sides (90° & 270°).
- Exhibits proximity effect.
- Sensitive to vocal plosives.
- Excellent sound isolation.
- Great for miking a single source.
- High gain-before-feedback.
- Very common in coincident and near-coincident stereo-miking techniques.
- Becomes more directional at higher frequencies (may take the shape of a supercardioid, hypercardioid, or even lobar/shotgun pattern).
- Becomes less directional at lower frequencies (may take the shape of a subcardioid pattern).
- Makes the typical default patterns of each diaphragm in dual-diaphragm multi-pattern microphones.
- The “Mid” Microphone In Mid-Side Techniques.
- Works on the pressure-gradient principle.
- Only achievable with an acoustic labyrinth covering the rear of the diaphragm.
- A 1:1 ratio of an omnidirectional and bidirectional pattern (superposition).
Most Common Mic Pattern In Studio, Stage, And Broadcasting
The cardioid polar pattern is by far the most popular and commonly used.
Its simple unidirectionality combined with its rear rejection makes it an excellent choice in most situations in the studio, on the stage, and in broadcasting.
Any time we need a clean, isolated sound source (which is most of the time), a cardioid microphone should be considered!
The Standard Unidirectional Polar Pattern
Though the term unidirectional refers to any microphone that is most sensitive in one direction (cardioid, cardioid-types, and lobar patterns), the word is often used synonymously with “cardioid.”
Perhaps this is due to the popularity of the cardioid pattern.
This may also be because the cardioid pattern is the quintessential unidirectional pattern. It is most sensitive to sound in one direction and completely insensitive to sound in the opposite direction.
Other microphone patterns may be more directional than the cardioid pattern, but they are so at the expense of rear lobes of sensitivity.
Null Point At 180° (Directly To The Rear)
As mentioned, the cardioid polar pattern is known for its rear facing (180°) null point.
This rear rejection to sound makes cardioid mics easy to position. Simply point the microphone at the sound source you want to pick up and away from the sound source you do not want to pick up.
The most common exploitation of the rear-facing null point is with stage monitors. Cardioid mics excel when placed in front of but pointing away from stage monitors. This allows the singer to sing into the mic (which points at him or her) with high gain-before-feedback (because the mic points away from and rejects sound from the monitor).
Roughly 6 dB Less Sensitive At The Sides (90° & 270°)
So far we’ve established that the ideal cardioid polar pattern is a unidirectional pattern that is most sensitive on-axis (we’ll call it 0 dB at 0°). We’ve also stated that the cardioid pattern is not sensitive at all to its rear (we’ll call it -∞ at 180°).
As the angle changes to either side of 0° in the cardioid polar pattern (clockwise or counterclockwise), the sensitivity decreases symmetrically until we reach the rear null point.
In the ideal cardioid pattern, there is a decrease of 6 dB (relative to the on-axis sensitivity) as we pass by 90° (and 270° due to symmetry).
If we base our acceptance angle on the points of -6 dB in a polar pattern, the cardioid mic will have a 180° acceptance angle. This means the mic will likely pick up sound fairly consistently within 90° to either side of its on-axis line.
The cardioid’s acceptance angle is quite wide while remaining unidirectional.
Exhibits Proximity Effect
The cardioid polar require requires the back of the diaphragm to be exposed to external sound pressure (albeit through an acoustic labyrinth that alters the phase and sometimes the amplitude of the sound waves).
This means that the diaphragm moves based on the difference in sound pressure between the front and back of the diaphragm. In other words, the cardioid polar pattern is based on the pressure-gradient acoustic principle.
Microphones that work on the pressure-gradient principle (essentially every mic that is not omnidirectional) exhibit proximity effect.
Since the cardioid diaphragm’s back side is encompassed in an acoustic labyrinth, the typical cardioid mic will not exhibit as much proximity effect as, say, a bidirectional mic (which has both diaphragm sides equally exposed).
For a more in-depth look at the microphone proximity effect, check out my article What Is Microphone Proximity Effect And What Causes It?
Sensitive To Vocal Plosives
Having both sides of the diaphragm exposed to external sound pressure also makes the cardioid microphone sensitive to vocal plosives.
Basically vocal plosives are tiny gusts of wind that come from hard consonant sounds in spoken language. The plosive energy is very transient and can cause a big difference in sound pressure between the front and rear of the diaphragm. This quick but large variation in pressure causes plosive “pops” to appear in the mic signal as the diaphragm/capsule is overloaded.
Similarly, cardioid microphones are sensitive to wind noise.
To learn more about vocal plosives and how to rid of them at the source, check out my article Top 10 Tips For Eliminating Microphone Pops And Plosives.
Excellent Sound Isolation
Due to the rear rejection and unidirectionality of the cardioid pattern, cardioid mics work wonders at isolating individual sound sources.
The wide (180°) acceptance angle of the typical cardioid also gives some leeway as to the dynamic positioning of or mic movement relative to the sound source.
By positioning a cardioid mic properly, we can essentially isolate a single sound source.
This works best when close-miking a source that does not have any other sound sources near or behind it. It helps if the “unwanted” sound sources are behind the microphone in the direction of the cardioid’s rear null point.
Sound isolation is essential in loud environments like the live room of a studio. It’s also essential is noisy live stages and venues. Isolation also plays a big role in less-that ideal recording environments and even in sound proof rooms to really hone in on a specific source, which brings us to our next point:
Great For Miking A Single Source
Cardioid microphones are a go-to for miking single sources. Common single-source cardioid miking situations include:
- Spot-miking single instruments in a large ensemble.
- Miking individual drums or percussion elements in a drum kit/ or percussion set up
- Capturing a single person’s voice in the studio or in the field
- Close-miking instruments in the studio and on stage
I put together a short list of microphone positioning tips here: Top 23 Tips For Better Microphone Placement.
The cardioid microphone, when positioned correctly, may achieve a great deal of gain-before-feedback in live sound reinforcement situations.
This is due to the rear null point, which makes it easy to position the mic: simply point it away from any monitors or loudspeakers.
Feedback loops are created when a microphone picks up too much sound from a loudspeaker that is emitting that same microphone’s signal.
Simply pointing the cardioid away from a live speaker will allow for excellent gain-before-feedback.
To read more into microphone feedback and how to reduce or rid of it, check out my article What Is Microphone Feedback And How To Eliminate It For Good.
Very Common In Coincident And Near-Coincident Stereo-Miking Techniques
As we’ll discuss in the next section, cardioid microphones are very popular in coincident and near-coincident stereo-miking techniques. This kind of ties into the fact that cardioid’s work great in close proximity to their sound sources.
To read my take on the best stereo-miking techniques (which includes many coincident and near-coincident techniques), check out my article Top 8 Best Stereo Miking Techniques (With Recommended Mics).
Becomes More Directional At Higher Frequencies
Like all microphones, real cardioid microphones will generally become more directional at higher frequencies.
We’ll see in the microphone examples that, sometimes, the polar response pattern may begin resembling a supercardioid/hypercardioid pattern at higher frequencies with a rear lobe of sensitivity.
This is partly due to the fact that, at higher frequencies, phase differences become sporadic between the front and back of the cardioid diaphragm, making amplitude differences more important to microphone directionality.
Becomes Less Directional At Lower Frequencies
In reality, microphones become less directional at lower frequencies.
In the case of cardioid microphones, they may even lose their rear null point at lower frequencies and exhibit a more subcardioid/wide cardioid polar pattern.
Makes The Typical Default Patterns Of Each Diaphragm In Dual-Diaphragm Multi-Pattern Microphones
Multi-pattern microphones typically have dual-diaphragm capsules that feature two back-to-back cardioid diaphragms (with the proper housing and rear side acoustic labyrinths).
Combining the signal amplitudes and polarities of these two cardioid “capsules” yields various other polar patterns.
The “Mid” Microphone In Mid-Side Techniques
A cardioid mic provides the mid channel in the famous mid-side stereo-miking technique.
The side channel is provided by doubling up the signal of a perpendicularly positioned bidirectional mic. Panning the signals left and right and flipping the phase of one of them yields the side information that disappears when the mix is collapsed to mono.
Works On The Pressure-Gradient Principle
As mentioned, the cardioid polar pattern is only achievable with the pressure-gradient principle. This means that both the front and back sides of the mic diaphragm must be exposed to external sound pressure.
Only Achievable With An Acoustic Labyrinth Covering The Rear Of The Diaphragm
The directionality of the cardioid microphone is brought about by carefully adjusting the path of sound before it reaches the rear side of the diaphragm. This is done with what is known as an acoustic labyrinth.
A 1:1 Ratio Of An Omnidirectional And Bidirectional Pattern
One way of explaining the cardioid polar pattern is as a superposition of the omnidirectional and bidirectional polar patterns.
As we see below in the diagram/equation, the positive polarities of the omni and bidirectional polar patterns add up to give the cardioid essential +2 in phase at 0° on axis.
Conversely, at 180°, the positive polarity of the omnidirectional pattern cancels out with the negative polarity of the bidirectional pattern, causing the rear null point of the cardioid.
As we move further off-axis, the negative polarity of the bidirectional pattern’s rear lobe slowly combines with the positive polarity of the omni and reduces the sensitivity of cardioid symmetrically between 0° and 180°.
This is indeed a clever way of explaining the cardioid polar pattern.
How Is The Cardioid Polar Pattern Achieved?
The cardioid microphone polar pattern is peculiar indeed. So how is this polar pattern achieved in various microphones?
Let’s start by defining cardioid microphones as working on the pressure-gradient principle. This means that both sides of a cardioid mic’s diaphragm are open to external sound pressure.
The diaphragm moves according to the pressure difference between its front side and rear sides. As we know, the diaphragm movement is what yields our mic signal.
- When the pressure is greater on the front side of the diaphragm, the diaphragm will move toward the rear.
- When the pressure is greater on the rear side of the diaphragm, the diaphragm will move toward the front.
- If there is equal pressure on both sides of the diaphragm, the diaphragm will not move.
So both sides of a cardioid mic’s diaphragm are open to external sound pressure, but they are not equally open to this pressure.
By integrating an acoustic labyrinth in the rear part of the capsule, microphone manufacturers cleverly offset the phase (and may alter the amplitude) of the sound waves before they hit the rear of the diaphragm.
As mentioned in the above bullet points, if there’s even sound pressure on both sides of the mic diaphragm, the diaphragm will not move and no mic signal will be outputted.
So in order to achieve the rear null point in the cardioid pattern, sound coming from the rear must reach the back of the diaphragm at the same time it reaches the front.
If it takes a sound wave traveling from the rear (180°) time T to get from the rear outer part of the acoustic labyrinth to the front of the diaphragm, then it must take that same sound wave time T to travel from the same point through the labyrinth to the rear of the diaphragm.
By offsetting the time it takes sound to reach the rear of the diaphragm, manufacturers cleverly achieve the unidirectional cardioid polar pattern with its highly effective rear null point at 180°.
Note that the timing difference is very small since sound travels quickly. However small, though, this phase offset is responsible for the unidirectional cardioid (and cardioid-type) polar pattens.
The Cardioid Polar Pattern Is Critical For Achieving Other Patterns In Multi-Pattern Microphones
Most multi-pattern microphones utilize back-to-back cardioid capsules in order to attain their other polar patterns. For example:
- Omnidirectional polar pattern is achieved by combining 2 back-to-back cardioid capsules at equal amplitude in-phase.
- Bidirectional polar pattern is achieved by combining 2 back-to-back cardioid capsules at equal amplitude out-of-phase.
For more versatile capsules like the famous AKG CK12 (which features 2 diaphragms and a shared backplate), many other polar patterns are attainable by different combinations of mic signals from each diaphragm.
The AKG CK12 and other well-known capsules are discussed further in my article What Is A Microphone Capsule? (Plus Top 3 Most Popular Capsules).
When Should You Use A Cardioid Microphone?
The cardioid microphone pattern is the most popular mic polar response pattern in the world. From the studio to the stage to the broadcast location and everywhere in between, there is likely a microphone role that would benefit most from a cardioid polar pattern.
The simple unidirectionality and rear rejection make cardioid microphones ideal in many situations. Let’s look at the applications that benefit most from cardioid mics:
Best Applications For Cardioid Microphones
- Directly in front of foldback monitors in live sound reinforcement situations
- When high gain-before-feedback is needed
- To close-mic/isolate single sound sources in noisy environments
- To mic individual closely positioned sound sources (like the drums of a drum kit)
- To capture clean audio in less-than-ideal environments
- When proximity effect is wanted
- For maximal rejection of sound to the rear
There are many situations that call for cardioid microphones. However, the other polar patterns certainly outperform cardioid from time to time. The following are situations where a cardioid mic (or cardioid mics) is not the best choice:
When Shouldn’t You Use A Cardioid Microphone?
- If the sound source will be moving around the microphone (off-axis colouration)
- If vocal plosives are a huge issue
- If the proximity effect is not wanted
- To record the most natural room/ambience
List Of Miking Techniques With Cardioid Microphones
Here is a list of miking techniques that include cardioid microphones:
- Close-Miking (mono)
- XY Pair (stereo)
- Mid-Side (stereo)
- DIN Pair (stereo)
- EBS Pair (stereo)
- NOS Pair (stereo)
- ORTF Pair (stereo)
- RAI Pair (stereo)
- Stereo Ambient Sampling System (stereo)
- Spaced Cardioids (stereo)
- Ambisonic Array (surround sound)
- Ambisonic Microphone (multiple cardioid capsules for surround sound)
- Cardioid Trapezoid (surround sound)
- Corey/Martin Tree (surround sound)
- Double Mid-Side Array (surround sound)
- Double ORTF Array (surround sound)
- Fukada Tree (surround sound)
- Hamasaki Surround System (surround sound)
- INA-5 (surround sound)
- IRT Cross (surround sound)
- OCT-Hamasaki (surround sound)
- OCT-IRT (surround sound)
- OCT Surround (surround sound)
- Spherical Microphone Array (surround sound)
- Wide Cardioid Surround Array (surround sound)
For more information on stereo miking techniques, check out my article Top 8 Best Stereo Miking Techniques (With Recommended Mics).
Cardioid Microphone Examples
- Shure SM57
- Shure SM58
- Neumann KM 184
- Rode NT1-A
- Shure WL185
The Shure SM57 is a top-address moving-coil dynamic microphone with a cardioid polar pattern. It is one of the most popular mics in the world and is often referred to as the “studio workhorse.”
This microphone is inexpensive, rugged, and is a favourite “jack-of-all-trades” of audio engineers in studios across the globe.
The Shure SM57 Polar Response Graph
The Shure SM57, like most cardioid microphones, is closest to the ideal cardioid pattern at 1-2 kHz. We see above that the 57’s pattern approximates subcardioid at lower frequencies (shown at 125 Hz) while in the upper mid-frequencies (4-8 kHz), the SM57 develops a rear lobe reminiscent of a supercardioid or hypercardioid.
That being said, the frontward response of this unidirectional microphone is what matters most and the SM57 is very consistent within 60° of its on-axis response. In practice, this means the cardioid pattern of the SM57 is highly effective!
The SM57 is not overly sensitive in the high-end frequencies, so it makes sense to omit the 16 kHz (octave above 8 kHz) pattern that is often present in polar response graphs.
The Shure SM58, like the SM57, is a top-address moving-coil dynamic microphone with a cardioid polar response pattern. It is the most popular live vocal microphone in the world.
The low price point, incredible toughness, and rear rejection of its cardioid pattern make the SM58 the go-to mic for live vocals.
The Shure SM57 Polar Response Graph
The Shure SM58, like its aforementioned relative the SM57, displays the most ideal cardioid polar pattern between 500 Hz and 2,000 Hz. In this range, the microphone exhibits the general 6 dB attenuation at the sides and a great deal of rejection at the 180° rear null point.
At lower frequencies, the SM58 takes on a more subcardioid polar patter (see the 125 Hz polar pattern). At higher frequencies (up to 8 kHz), the mic’s frontward directionality changes very little, which a quality. However, at these higher frequencies, the rear null point is replaced by somewhat of a rear lobe of sensitivity.
The SM58 is not overly sensitive in the high-end frequencies, so it makes sense to omit the 16 kHz (octave above 8 kHz) pattern that is often present in polar response graphs.
Neumann KM 184
The Neumann KM 184 is a small-diaphragm top-address true condenser microphone with a cardioid polar pattern.
This microphone excels in the studio with its flat frequency response, excellent transient response, and incredibly consistent polar response. The KM 184 sees a lot of action by itself in close-miking mono techniques and in coincident and near-coincident stereo-miking techniques.
The Neumann KM 184 Polar Response Patter
Small-diaphragm condensers are known for their consistency when it comes to polar patterns. The high-end Neumann KM 184 is a prime example of this generality.
As we can see in the split graph shown above, even at the low-end of 125 Hz, the KM 184 maintains 16 dB or rear rejection and the typical 6 dB of side rejection. The rear null point holds true from 250 Hz to 4,000 Hz, which covers a very wide range. Even at higher frequencies, the KM 184 maintains its cardioid pattern extremely well.
The Rode NT1-A is a flagship microphone from the Australian microphone manufacturer Rode. It is a large-diaphragm side-address electret condenser microphone with a cardioid polar response pattern.
The low self-noise, accurate response, and relatively low price point make the NT1-A an excellent choice for home, project, and professional studios alike.
The Rode NT1-A Polar Response Graph
Rode does not give away too much information here, showing only 3 frequencies in its polar response graph.
However, with the info provided, we see something counterintuitive with the NT1-A. It actually becomes less directional at 4 kHz as compared to 1 kHz. Typically microphone polar patterns begin tightening up above 1 kHz while loosening below 1 kHz. The polar response graph of the NT1-A tells us otherwise.
The Shure WL185 is the cardioid version of Shure’s WL180 line of subminiature lavalier/lapel electret condenser microphones.
The WL185 is technically a top-address mic. As with most lav mics, the WL185 sees most of its use attached to the clothing or in the hair of speakers in film and video applications.
The Shure WL185 Polar Response Graph
The polar response graph of the Shure WL185 shown above resembles a simple ideal cardioid pattern. There are no distinctions between different frequencies.
This is a fairly common occurence with miniature lavalier/lapel microphones. Some manufacturers will not even include a polar response graph for their lav mics since their small size makes them very consistent and allows them to be closer to ideal across the spectrum of their frequency response.
All The Different Microphone Polar Patterns
Here’s a list of all the different polar patterns you’ll likely encounter when using microphones:
By clicking the links of each polar pattern title, you’ll be brought to a mynewmicrophone article that focuses on that specific polar pattern.
- Omnidirectional: picks up sound equally in all directions.
- Bidirectional: picks up sound symmetrically in the front (0°) and back (180°) with equal sensitivity but opposite polarity. Bidirectional patterns have null points at their sides (90° & 270°), which yields a “ring of silence” in 3D space. Their polar pattern looks like a figure-8 in 2D.
- Cardioid: unidirectional pattern with a null point at the rear (180°) and roughly 6 dB decrease in sensitivity at its sides (90° & 270°) compared to on-axis (0°).
- Supercardioid: unidirectional pattern with a narrower on-axis response than “regular” cardioid. Null points at 127° & 233°, which yields a “cone of silence.” There’s roughly a 10 dB decrease in sensitivity at its sides (90° & 270°) and a rear lobe of sensitivity with 10 dB less sensitivity (at 180°) compared to on-axis (0°).
- Hypercardioid: unidirectional pattern similar to supercardioid with a narrower on-axis response than “regular” cardioid. Null points at 110° & 250°, which yields a “cone of silence.” There’s roughly a 12 dB decrease in sensitivity at its sides (90° & 270°) and a rear lobe of sensitivity with 6 dB less sensitivity (at 180°) compared to on-axis (0°).
- Subcardioid/Wide Cardioid: A unidirectional pattern with a wider response than “regular” cardioid. Subcardioid can be thought of as a midway point between cardioid and omnidirectional.
- Shotgun/Lobar: An extension on the supercardioid and hypercardioid polar patterns. The use of an interference tube in front of an already highly directional capsule yields the extremely directional shotgun/lobar pattern. These patterns generally have a rear lobe of sensitivity and sometimes even have small side lobes of sensitivity.
- Boundary/PZM (Hemispherical): The hemispherical polar pattern found on boundary and pressure zone microphones. These patterns are achieved by placing the mic capsule flush to a flat surface and then placing the microphone itself at a surface/boundary within an acoustic space. The capsules themselves can be any polar pattern, though omnidirectional capsules are often preferred.
For an in-depth definition of all the polar response patterns listed above (and much more), check out my article The Complete Guide To Microphone Polar Patterns.
Cardioid-Type Polar Patterns
- Subcardioid/Wide Cardioid: 7:3 ratio of omnidirectional to bidirectional (less directional than the basic cardioid).
- Cardioid: 1:1 ratio of omnidirectional to bidirectional.
- Supercardioid: 5:3 ratio of omnidirectional to bidirectional (more directional than the basic cardioid).
- Hypercardioid: 3:1 ratio of omnidirectional to bidirectional (more directional than the basic cardioid).
How do cardioid and supercardioid polar patterns differ? Supercardioid mics are more directional than cardioid mic. They are less sensitive to the sides at the expense of a small rear lobe of sensitivity (cardioids have rear null points). Supercardioid mics are often preferred in film while cardioids are typically chosen in audio-only applications.
For a detailed look at supercardioid microphones, check out my article What Is A Supercardioid Microphone? (Polar Pattern + Mic Examples).
How do cardioid and hypercardioid polar patterns differ? Hypercardioid mics are more directional than cardioid mic. They are less sensitive to the sides at the expense of a small rear lobe of sensitivity (cardioids have rear null points). Hypercardioid mics are often preferred in film while cardioids are typically chosen in audio-only applications.
To learn more about the hypercardioid microphone pattern, check out my article What Is A Hypercardioid Microphone? (Polar Pattern + Mic Examples).
To learn more about all the microphone polar response patterns, check out my article The Complete Guide To Microphone Polar Patterns.