You’ve read tons of product descriptions…
And you see the same 3 words appear over and over…
Cardioid, Omnidirectional, and Figure-8.
But what do they actually MEAN?
And why are they SO important when choosing the right mic?
If you’ve got questions, and you want answers…
Then here’s what I have for you:
In this post, I’ve assembled this easy-to-read guide entitled…A Beginner’s Introduction to Microphone Polar Patterns.
A microphone’s polar pattern is the 3-dimensional space surrounding the capsule where it is MOST sensitive to sound.
The 3 basic patterns are:
Here’s a diagram showing how they look:
As you can see…
Other than the 3 basic patterns, you also see:
Some mics, known as “multi-pattern mics” allow you to switch between several polar pattern options as needed.
Now here’s where all this technology came from…
In the earliest days of microphone technology, there were only 2 polar patterns:
Originally known as “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.
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 rear, but almost completely deaf on the sides.
Eventually someone discovered that by combining the signals of BOTH omnidirectional AND figure-8 mics…
Here’s what happens:
The result became what we know today as a standard cardioid polar pattern.
Here’s a diagram to illustrate it:
Eventually engineers designed new cardioid capsules that were essentially hybrids of the original two designs. Soon afterward, came these next patterns:
The next major advancement came when someone realized that cardioid patterns could be made even MORE directional by mixing MORE figure-8 signal with LESS omni.
As a side effect, this would also create a small bulb of sensitivity emerging from the rear.
This new pattern became known as supercardioid, and the narrower version known as hypercardioid.
In this example diagram, I show how it works by combining 1 part omni with 2 parts figure-8:
Now let’s move on…
Rather than requiring a separate mic for every job…engineers came up with an ingenious idea to cram a TON of versatility into just one mic.
They realized that…simply by varying the output from two back-to-back cardioid capsules, you could recreate virtually any polar pattern imaginable.
And that’s how we eventually got the multi-pattern mics we use today.
Next up, let’s see how all these patterns are used to actually record stuff…
The advantage of using cardioid mics seems simple, right? It records where you point it, and ignores everything else. Which is why it is the obvious choice for vocal mics.
But here are some less-obvious examples when it’s ESPECIALLY useful:
Now they might seem ideal in most cases..but cardioid mics DO have drawbacks…
The two BIGGEST ones being:
Supercardioid and hypercardioid patterns, while essential for filmmakers, are not commonly used in the recording studio.
Because they are SO prone to off-axis spill…Omnidirectional mics aren’t nearly as popular as they were prior to the invention of the cardioid pattern.
But by no means does that make them irrelevant. For example…
Here are common situations when they’re preferable:
Compared to cardioid mics, omnidirectional mics offer the following advantages:
This last advantage is especially true with small diaphragm omni mics. That is why most precise measurement microphones (like Earthworks mics for example) are small diaphragm omni’s.
So why EXACTLY would you want a mic that was equally sensitive on both sides? It doesn’t seem very useful, does it?
The cliche example you always hear is…to record a duet of singers facing each other.
While it might be great in that situation…how often does that it happen? Almost never.
It’s much more common to use figure-8 mics for one of the following 3 reasons:
For stereo recording, figure-8 mics are required to perform both the Blumlein Pair, and Mid/Side stereo techniques.
With ribbon mics, the physical make up of the design often requires a figure-8 polar pattern. If you like ribbon mics for their sound, the figure-8 pattern simply comes as part of the package.
To isolate instruments in close proximity, figure-8 mics are ideal because they completely reject sound from the sides.
With smart positioning, you can achieve more isolation with a figure-8 mic than with any other polar pattern. One common trick is to place acoustic absorption at the rear end of the mic to block out any unwanted noises.
So now that you know all the basics of microphone polar patterns, it’s time to put this knowledge into practice.
While all these facts may be simple enough in theory…the only way to really get a feel for microphone polar patterns is to experiment.
Take some time to record different instruments, with different polar patterns, in different rooms…and listen to the differences in each combination.
Eventually you get a feel for what works and what doesn’t.