Do you know the Pattern to Perfect Sound?
Wrapping your Head Around Microphone Polar Patterns
Microphones, the audio paintbrush… there are so many to choose from and I’m sure at time choice can be a bit of a prison. However, if you keep your eye on practically every product description out there three distinct words will pop up more often than not Omnidirectional, figure-8 and Cardioid… but what do these words really mean and how do they apply to helping you select the right microphone for your application. Let's Break it down.
There is 3 basic microphone polar patterns, I have added a suggested set of microphones priced from low to high for each pattern as an example, do the gear junkie in you a favor and check them out on your way to understanding Microphone Polar Patterns. They are as follows:
- Starting out: Rode NT2-A
- Prosumer: Audio-Technica AT4050ST
- Professional: Neumann M150 Tube
- Starting out: Audio-Technica AT2050
- Prosumer: Blue Microphones Kiwi
- Professional: Neumann U87
- Mic 1 has an Omnidirectional pattern – meaning the entire Dark Blue area represents equal sensitivity to sound.
- Mic 2 has a Figure-8 pattern – meaning the two Lighter Blue areas on the front and back are more sensitive to capturing sound, while the sides reject sound a bit more effectively.
- Mic 3 has a Cardioid pattern – meaning the gray area in front of the mic is the most sensitive, the sides less sensitive, and the rear almost entirely reject sound from being captured.
Along with the 3 basic patterns, you will also see:
- Supercardioid: Similar to the standard cardioid pattern, but more narrow, with a small bulblike rear pickup pattern meaning it does not completely reject all sound from behind.
- Hypercardioid: Much like the aforementioned Supercardioid, but even more directional, with a larger bulblike rear pickup pattern.
These days getting your hands on “multi-pattern microphones” has become a whole lot more affordable, allowing you to switch between several polar patterns giving you a little more flexibility depending on your recording requirements at the time. Be forewarned though, not all mics are made equal.
But how did it all come to be?
Back in the day there were only 2 polar patterns:
As with all Origins stories they were not always known as Omnidirectional Microphones but rather “pressure” microphones, their diaphragms measured sound pressure at a single point in space.
Because they had no directional information, they were equally sensitive to sound from all directions. (Omni)
On the flip side, what we have come to know as the Figure-8 microphone was more commonly known as “pressure gradient” microphones, they measured the difference in pressure between either side of an open diaphragm.
This meant that they were very sensitive to sound from the front and Back, but almost completely rejected sound from the sides. (8)
The Birth of a Legend, enter Cardioid Microphones
Eventually one of those smart dudes in a white coat discovered that by combining the two signals (Omni + Figure 8) something magical happened…
The outcome would become a stage a studio staple for years to come, here’s what happened:
- On the frontend – the positive signals combine to be twice as strong.
- On the sides – the signal from the omni remains the same.
- In the rear – the negative signal of the figure-8 cancel out the positive signal of the omni.
The result became what we know today as a standard cardioid polar pattern.
Eventually even smarter dudes in even whiter coats designed new cardioid capsules that were “The Next Step” in the evolution of the newly discovered Cardioid Polar Pattern. Essentially a hybrid of the original two designs. Enter the Supercardioid and Hypercardioid:
These dudes realized that a cardioid pattern could be made more directional by mixing more of the figure-8 signal with less of the omni signal.
A happy coincidence, this would also create a small bulb of sensitivity from the rear.
This new pattern became known as the SUPERcardioid, and it's even narrower counterpart became the HYPERcardioid.
If the Frankenstein-esque experiment and subsequent creations didn’t make too much sense in words, don’t worry too much, we’ve got you covered. Below is a graphic representation of how these renegades of Audio Recording brought forth their new creations.
Ok so now that the proverbial “cat is out of the bag” in terms of what the patterns are and how they came to be, I thought it only fitting to leave you with a few tips on which microphones generally work best in specific situations. Keep in mind recording is an artform and there really is no “Right or Wrong” but you know how they say, “if it ain’t broke, why fix it?” here are a few tried and true examples to get you started.
When to Use Cardioids Microphones:
Because It pretty much records what you point it at, and ignores just about everything else. It’s kind of a no brainer for use when recording Vocals. But here are a handful of applications where the cardioid pattern really shines:
- On Stage – When sound is coming from every corner of the stage a cardioid mic is great for maintaining isolation and preventing feedback. (Check out the Shure SM58 the industry standard for Years now)
- Miking up a drum kit – Yes, a drum kit is technically “one instrument” but it consists of a multitude of individual pieces or instruments all placed in very close proximity to one another, isolation might seem impossible, it can be done though… with a few well selected cardioid mics and a little creative close placement you will be surprised at the level of separation you can pull off even before applying any kind of gate.
- Untreated Rooms – In rooms with poor acoustics, close-miking with cardioid mics can work wonders to minimizing the effects of harsh room reflections.
With all of this said Cardioid microphones may sound a little too good to be true and you would be right, for all the pros they do have a few cons:
The two biggest cons being:
- Proximity effect – A phenomenon exclusive to cardioid mics… The proximity effect boosts low frequencies when they are placed extremely close to the source they are meant to capture. An “inexperienced singer” for example, may not maintain a constant distance from the microphone when recording which would result in a fluctuation of the captured sound (Highs and Lows depending on how far or close the singer is to the microphone at any given point in the take while recording) you can see how this would cause problems.
- Off-axis coloration – With most cardioid mics, there is a drop in high-frequency sensitivity as sounds move further off-axis. Again, this could have a negative effect on the outcome of the recording if the “inexperienced singer” (in this example) does not exercise restraint in unconscious head movements.
Supercardioid and hyper cardioid patterns, while essential for filmmakers and broadcast, are not commonly found in the recording studio.
When to Use Omnidirectional Microphones
To be fair this polar pattern has taken a bit of a back seat since the introduction of the Cardioid polar pattern due to its tendency to capture off-axis spill… They are by no means in any danger of extinction though in fact they have found places where they are nearly indispensable. Her are just a few examples:
- Capturing the sound of a room when recording drums or guitar: Room mics.
- Capturing a wide sound source: Orchestras, Choirs, or grand pianos.
- Capturing a moving target: That acoustic guitar player who just happens to be feeling the music a little too much and can't seem to sit still.
- When recording in stereo: We will discuss Recording Techniques like the common A/B technique in upcoming blog posts.
In direct comparison to cardioid mics, omnidirectional mics offer the following Pros:
- Lower self-noise
- Immunity to proximity effect
- Less coloration of off-axis sounds
- A frequency range that typically extends a full octave lower
Having mentioned that one of the Pros of an omnidirectional microphone is that it has a frequency range that typically extends a full octave lower, I just want to point out that this is especially true with small diaphragm omnidirectional microphones.
When to Use Figure-8
At this point I'm relatively sure you are asking yourself, why I would need a microphone that captures audio from both sides? Fear not, there is a whole lot you can squeeze out of this proverbial audio paint brush and NO, not to recording a romantic duet… That almost never happens.
It’s more commonly used in the following situations:
- Stereo Recording: For stereo recording, figure-8 microphones are required to perform both the Blumlein Pair, and Mid/Side stereo techniques. (Don’t let these big scary words intimidate you as I assure you we will discuss miking techniques a little more in depth in a follow up blog post.
- Ribbon Microphones: With Ribbon Microphones, the physical make up of the design often requires a figure-8 polar pattern. If you like Ribbon Microphones (and believe me, you will!) for their sound, the figure-8 pattern simply comes as part and parcel.
- Maximum isolation of off-axis sounds: To isolate instruments in close proximity, the figure-8 microphones really work wonders because, for the most part, they completely reject sound from the sides. With creative positioning, you can achieve more isolation with a figure-8 microphone than any other polar pattern. One common trick of the trade is to place acoustic absorption at the behind the microphone to block out any unwanted noises.
Hopefully that will have helped demystify some of the common misconceptions surrounding microphone polar patterns, how they came to be and what each of them are best suited for. If you have any further questions please feel free to contact us as we are standing by and always happy to help.