A microphone with a bi-directional pickup pattern, AKA a Figure 8 mic, is handy in many recording situations, and not so handy in others.
Microphones pick up sound from very specific directions. Most mics default to picking up sound from just one direction, and are called “unidirectional” mics. These are really useful for lots of things, including live stage performances where there are monitor speakers pointing up at your face while you sing/speak. In such a situation, a unidirectional microphone will pick up your voice but will reject the sound coming at you from the monitor speaker (assuming you’re facing the audience), which is behind the mic. This is good because it helps prevent that all-too-familiar nasty screeching feedback through the PA that makes everybody cringe.
But there are other microphones, many of which are essential to recording studio scenarios, that pick up sound from multiple directions at once, either from all directions (“omnidirectional”) or from just the front and back. Microphones with the latter type of pickup pattern are usually called bi-directional, or “Figure 8” mics.
By the way, a microphone’s directionality is also referred to by the term “polar pattern.”
What Is the Figure 8 microphone pickup pattern good for?
So why would anyone want to use a figure 8 mic? Oh, there are several cool things you can do with these, including:
- Recording two voices at the same time
- Recording a singing guitarist/instrumentalist
- Recording in stereo
Recording two voices at the same time
You could place a Figure 8 mic between two singers to record them both and not have to use two mics. Normally, in order to record two people simultaneously with only one mic, they would have to crowd their faces together in order to get their voices into the pick-up area at the front of a unidirectional mic. But with a Figure 8 pattern, one person could stand on one side of the mic, and the other on the opposite side, facing one another. This is much more comfortable, and there is an added advantage of being able to see the other person for timing, cues, and other communication.
Another handy use for a Figure 8 mic would be for a podcast or radio interview. The interviewer could be on one side of the mic, and the interviewee could be on the other.
Recording a singing guitarist/instrumentalist
If you only have one mic to record a singing guitarist, you might be tempted to just record the guitar first, and record the singing afterward, as two separate tracks. With unlimited tracks available in today’s computer recording world, this is easily done. That is the way I, as a singing guitarist myself, always do it.
However, it isn’t always easy for a singing guitarist to perform this way. He or she may be much more comfortable doing both at the same time, or you might want to record the take with vocals and guitar simultaneously for many reasons. Using a Figure 8 polarity pattern, you can place a mic between the performer’s mouth and guitar to pick up both sounds clearly. But a Figure 8 mic rejects sounds from its sides, just like the unidirectional mic rejects sound from the rear, so the separation of the two sounds is better and any extraneous room sound will be minimized by the side rejection.
Recording in stereo
There are several stereo recording techniques that involve Figure 8 mics. One of the most popular is something called the “mid-side” technique. For this you need two different kinds of microphones – one unidirectional and one figure 8 mic – and the signals from the two differently-patterned mics get combined to produce a very flexible and cool-sounding stereo recording.
Another figure 8 stereo technique is called a “Blumlein Array,” where you cross two Figure 8 mics.
And a less-known stereo recording scheme uses two Figure 8 mics facing forward, spaced about 20 cm apart. This is called the “Faulkner Array.”
What are the disadvantages of the Figure 8 polar pattern?
The potential problem with using a Figure 8 pattern is recording sounds you don’t want, including computer noises, a fan, or a snoring dog. Some microphones are “multi-pattern” mics, which means there is a switch on the side that you can use to change the pattern from unidirectional or “cardioid” (named because its pick-up pattern is heart-shaped), to Figure 8, to omnidirectional (picks up sound equally from all directions). If you have that switch set to Figure 8, you must remember that it picks up sound from behind just as well as from the front. So if there is something behind the mic, your microphone will amplify those sounds!
If you are not familiar with the little icons that represent the different patterns, you could end up with lots of dog snoring in your audio. My friend with the dog had gotten a multi-pattern mic, and had moved the switch to what looked like an infinity sign (you know – the sideways “figure 8”!), thinking it would be maximum loudness or something similar. Of course what that icon REALLY meant was “bi-directional/Figure 8.” Once she switched to the unidirectional pattern (usually a heart-shaped icon), we heard a lot less dog snoring in her audio.
If your recordings have a lot of echoes or reverby sound in them, or have a lot of extraneous noise, you might want to double-check what pattern is selected on your mic, assuming it is of the multi-pattern variety.
Now that you know the pros and cons of using a Figure 8 polar pattern, use that knowledge for good. I expect to hear cool stereo sounds, or at the very least, less noisy ones, coming from you in the future.
Ken Theriot is a singer, guitarist, and recording enthusiast who runs the Home Brew Audio blog, whose mission is to demystify audio recording for all the regular people out there who thought home recording was limited to the realm of tech geeks and audio engineers with lots of school and tons of expensive gear.
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