Multi-Pattern Microphones: What, Where and How?
Looking to isolate sound sources and minimize feedback? This overview of the basic mic polar patterns will help you determine which pattern is right for you.
Is it really a cardioid world? While the cardioid polar pattern is undoubtedly the most often used in live sound applications (after all, the ubiquitous Shure SM57 and SM58® microphones are both cardioid types), there's a case to be made for models that, with the flip of a switch (or the changing of a head) offer directionality options.
Being able to custom-tailor what the mic picks up and rejects by understanding the pattern's coverage angle can help you reduce feedback, isolate sound sources from one another, control proximity effect, and create a sonic image in both live and recording applications. Plus, if you have a limited selection of mics in your locker, a multi-pattern mic is really two mics in one.
Before we get into some specific benefits for the stage and studio, let's review the basic polar (or pickup) patterns. There are three basic types: omnidirectional, unidirectional and bidirectional (also called figure-of-eight).
Polar Pattern Refresher
Often misunderstood, a mic's polar pattern defines how it responds to sounds coming from different directions. The polar pattern tells you how the mic should be placed to maximize pickup of the desired sound source while minimizing feedback or pickup of unintended sound sources.
Omnidirectional polar pattern
An omnidirectional (or 'omni') microphone picks up equally from all directions since it has the same 360-degree output regardless of its orientation to the sound source. Its polar pattern is a sphere, and on paper, it looks like a nearly perfect circle. An omnidirectional mic can pick up a group of people sitting around a table, but it can't be aimed to favor one source over another. That means it is also prone to feedback.
Unidirectional Polar Patterns
A unidirectional mic is most sensitive from sound coming from one direction (with one notable exception: the bidirectional mic, but more about that to come). A 'uni' mic picks up less ambient noise than an omni type and is less susceptible to feedback when used with a sound system. There are several different types:
Cardioid polar pattern
The most common unidirectional pattern is the cardioid. It gets its name from its resemblance to a heart. It is most sensitive to sounds coming from in front of the mic and least sensitive directly behind the mic. A cardioid mic has a useful pickup angle of 131 degrees, so it can accommodate one or two singers and is forgiving enough to still pick up a vocalist with a wandering mic technique. The cardioid pattern offers very good feedback rejection.
Subcardioid polar pattern
Subcardioids, sometimes called "wide cardioids," are only slightly more directional than omnidirectional mics and slightly less directional than cardioids. They are most easily distinguished by their rear sensitivity, which is 3-10 dB lower compared to their front sensitivity. The subcardioid pattern allows wide, even, natural pickup and can capture a group of instruments or vocalists with very little proximity effect. They are, however, prone to feedback.
A supercardioid mic has a tighter pickup angle than a cardioid, but unlike the cardioid, it offers more side rejection. It is, however, slightly sensitive to sound sources that are directly behind the mic. A supercardioid provides better isolation from room noise and nearby instruments and can be more resistant to feedback than a cardioid mic, but it requires the user to maintain a more consistent position directly in front of the mic.
Hypercardioids feature some of the characteristics of a bidirectional microphone (described below) in that they have more sensitivity to the rear; however, they reject sound well from the sides and are exceptionally good at rejecting feedback. Because they are so directional, they require very precise placement to the source. Like a supercardioid pattern, the hypercardioid provides extreme rejection of ambient sound sources.
Bidirectional or Figure-of-Eight polar pattern
A bidirectional mic, sometimes called a figure-of-eight, is equally sensitive to sounds coming from the front and rear of the mic and least sensitive to sounds coming from the sides. Bidirectional mics have a very narrow pickup angle, which makes them useful for isolating one voice, or instruments that are surrounded by other sound sources, as long as there is nothing directly behind the mic. They are useful for picking up two sources that are positioned side by side. The deep null rejects everything else.
Now, let's look at them one by one.
Large, 1" dual-diaphragm side-address condenser, with switchable patterns.
- Cardioid on drum overheads or guitar amps
- Bidirectional between congas or toms
- Omni for ambient mics for IEM mixes
- Excellent stereo room mic pair in Mid/Side (cardioid/bidirectional setting)
- Great spaced omni for piano
- Bidirectional for two background singers on one mic, or omni in an isolation booth to eliminate proximity effect and
- reduce plosives
- Use them everywhere! Cardioid for drum overheads, bidirectional between toms and congas, supercardioid hanging on a guitar amp
- A pair of cardioids can normally fit under the lid of a piano (using an A75M Universal Mic Mount) allowing you to close the lid and reduce bleed
- With all available heads, a stereo pair can perform any stereo technique (XY, Mid Side, Blumlein, Spaced Omni, Recorderman, ORTF)
- Brilliant on acoustic guitar and drum toms
- Excellent piano mic
Dual-diaphragm handheld condenser mics with a variety of polar pattern options to further reduce feedback and handle a variety of challenging mic techniques.
- A good choice for switching between IEM singers and floor monitor singers
- Cardioid for IEMs allows a little ambience and supercardioid offers better gain before feedback in a floor monitor
- Hypercardioid setting offers great rejection for unconventional stage and PA placements (e.g. PA behind the stage)
- Subcardioid setting is perfect for Q&A mics, broadcast interviews, or TV show host mics
- Offers a forgiving wide pattern
- Hypercardioid offers exceptional rejection and large-diaphragm condenser-like sound quality, allowing a scratch track to be used in the final mix
- Cardioid is also a great snare and bass amp mic
- Good for an artist who is comfortable holding a mic while tracking
- Handling noise and plosives are not issues and vocals sound like they were recorded using a stand-mounted, high-end large-diaphragm condenser mic
Understanding Mic Specs
Multi-pattern mics offer exceedingly specific sound isolation that will allow you to tailor the mic to the sound source or even the vocal style of the singer. They can be used to reduce feedback, control bleed in live recordings, and create sonic images using the full spectrum of stereo-miking techniques. According to pro audio expert Hugh Robjohns, "The one big advantage of a multi-pattern mic is that it affords the opportunity to experiment easily, so make use of that opportunity whenever you can. You'll be surprised at how often cardioid really isn't the best choice!"
Rather see and hear a discussion of polar patterns? Check out this Shure video.
For a more comprehensive discussion of mics, mic placement, and recording techniques, download our Microphone Techniques for Recording booklet.