Welcome to part four of the Building Your Own PA blog series. So far we’ve looked at why having a good PA is important, and we’ve examined key components including mixers as well as speakers and amplifiers. This time around, we’ll turn our attention to the topic of microphones. Quality mics are essential because they’re the point of contact between sound and your PA system. If your mic doesn’t do a good job reproducing your vocals or instruments, it doesn’t matter how good the rest of your system is.
There are several factors to consider when choosing mics for your PA, including polar patterns, frequency response, durability, what kind of instrument you’ll be using it on and more. Let’s dive in and explore so you can get the right mics for your unique PA setup.
Perhaps the biggest problem you can face with a PA system is keeping feedback at bay. A feedback loop is created when sound from the speakers is picked up by the mic, sent back to the speakers and is then picked up by the mic again. As you’ve probably experienced yourself, the sound of feedback is unpleasant - even painful - and can distract the audience and performers.
One of the best defenses against onstage feedback is using a unidirectional mic. (For basic info on microphone pickup patterns, read this article.) Typical stage mics have a cardioid pattern, which picks up more from the front and less from the rear and sides. If your mics are behind the main speakers (as they always should be), and pointing away from the monitors, the rear rejection of a cardioid will help reduce the potential for feedback.
Two other variations of cardioid are hypercardioid and supercardioid. These patterns reject even more of the sound coming from the sides than a cardioid mic, making them more directional.
More directionality reduces the chances of feedback if correctly placed, because the mic picks up less sound coming from the speakers. It also means less pick up of “off-axis” sounds (captured from the less sensitive parts of the pattern, such as the rear on a cardioid mic), which have lower fidelity than sounds picked up directly into the mic.
Unlike instrument mics, vocal mics feature built-in windscreens. Vocal mics usually have a round protrusion around the capsule to accommodate the built-in windscreen.
Internal windscreens not only reduce pickup of wind noise at outdoor venues, they also reduce breath noise from the singer. If you try singing into an instrument mic that has no internal windscreen, you’ll notice that not only will it pick up more breath noise, but also more “plosives” - those popped consonant sounds (especially “p” and “b”), which are definitely not desirable. Try to avoid miking a singer with an instrument mic.
A live sound environment is not as controlled as a recording studio. As a result, stage microphones tend to get banged around, especially handheld vocal mics. They also get exposed to the elements when used in outdoor performances. For these reasons, stage mics need to be heavy duty.
The great majority of vocal mics are dynamic mics, which are less fragile than condenser mics. Most dynamic mics have the added benefit of handling higher SPL (sound pressure levels, i.e., volume) before distorting than condensers. This is especially important on instrument mics. They also tend to cause less feedback. Finally, dynamic mics don’t require phantom power from the mixer, like condenser mics do.
And if you’re willing to spend extra for a vocal mic, there are good handheld condensers available that are designed to be more durable than studio condenser. Because of their superior reproduction of highs and transients (the initial attack of a sound), they can offer better quality for some singers. A good example is the AKG C7, which is a supercardioid condenser vocal mic.
Make the Right Choice
When you’re buying mics for your PA system, it’s not a time to hunt for bargains. Quality mics are better built, and will last longer through the use and abuse that stage mics are prone to.
You want to get the right mics for the right applications. Here are some suggestions for the mic types to get for common live-sound applications:
- Vocals: handheld dynamic with unidirectional pattern such as the AKG P5i.
- Kick drum and floor tom: large-diaphragm dynamic such as the AKG D112MkII.
- Snare drum: dynamic instrument mic such as the AKG D40 or P4
- Drum overhead: small diaphragm condenser: AKG C451B or P170
- Toms: dynamic instrument mic or dedicated clip-on tom mic such as the AKG C518M, which is a condenser
- Guitar cabinet: dynamic instrument mic such as the AKG D40 or P4
While there are thousands of options available, if you keep in mind the basic principles outlined in this article, you’ll be able to choose mics for your PA system that will give you years of great performance.
Stay tuned for the next installment of this series, where we’ll look at signal processing for live sound. And if you have any questions about choosing mics for your PA system, let us know in the comments section and we’ll help you narrow it down.
First published in the HARMAN Insights Blog by Mike Levine, former editor of Electronic Musician. Mike has written numerous articles on music technology and recording.