Omni also exhibits significantly less proximity effect than cardioids. One result is that omnis are somewhat less sensitive to the movements of an animated vocalist. Another is that omnis tend to have less need for EQ. As mentioned earlier, while omnis pick up 360 degrees of sound, they tend to be more directional as frequencies increaseespecially in larger capsules.
Figure 8 or bidirectional pattern
The figure 8 or bidirectional pattern is equally sensitive on the two opposing faces of the microphone, yet rejects sound from the sides.This pattern does exhibit the proximity effect found in cardioid patterns.
The figure 8 is excellent for capturing a duet or face-to-face interviews with a single mic.The —40dB side rejection spec also makes it great for isolating an instrument like a snare from the rest of the drum kit. Figure 8 is also one of the key components of M/S (mid-side) mikingan advanced stereo recording technique well look at little later.
Super-cardioid pattern
The super-cardioidpattern exhibits an even narrower area of sensitivity than the classic cardioid and is used for very sonically focused recording. Super-cardioid is great for zeroing in on that perfect sweet spot for instruments such as piano or drum.This pattern is also ideal for live recording sessions where isolation is important, including minimizing bleed between a vocalist and their own instrument.
Single pattern vs. multi-pattern mics
The most inexpensive way to make a microphone is with a single fixed pattern. Cardioids have openings in the backs of the capsules that produce the physics of a unidirectional pattern.This is an inherently fixed pattern design. An omni- directional pickup pattern can be achieved by sealing the back of the capsule, resulting in another fixed pattern. Super-cardioids employ yet a different design. In most cases, different back-end electronics are required for each pattern, thus making it difficult to make interchangeable capsules.
Figure 8 patterns are | The super-cardioid |
sensitive on opposing sides | pattern has an even |
and exhibit strong rejection | greater focus of sensitivity |
at 90 degrees off axis | than cardioid |
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In multi-pattern microphones, two cardioids combine
in different ways to create other patterns
The secret to building a single mic with multiple pickup patterns is placing two cardioids back-to-back in combination with various electronic tricks. An omni- directional pattern occurs as the result of wiring two back- to-back cardioids in phase with each other. Similarly, those same two opposing cardioids wired out of phase yield a figure 8 or bi-directional pattern*. Tweaks to the polarity and output level result in a super-cardioid pattern. While the presence of two high-quality diaphragm/backplate assemblies increases the cost, this solution provides the best polar pattern performance and is still significantly less expensive than buying multiple microphones in order to have a choice of patterns at your disposal.
| | 90 | |
30dB | 120 | | 60 |
20dB | | | 30 |
| 150 | |
10dB | | | |
0dB | 180 | | 0 |
10dB | | | |
| 210 | | 330 |
20dB | | | |
30dB | 240 | | 300 |
| | 270 | |
| 100 Hz | 1 kHz | 10 kHz |
All microphones are less sensitive to high frequencies off axis (omni example shown)
This approach to capsule design can be seen in the M-Audio Solaris. The Solaris employs an opposing pair of the same diaphragm/backplate assemblies, thus allowing for the selection of multiple patterns via switches on the body of the mics.
*Tip: Note that the out-of-phase wiring of the two sides of a figure 8 capsule can play tricks on the uninitiated. One side will sound strange to a vocalist or speaker who is simultaneously monitoring the mic
Choosing & Using Microphones | 7 |
