Microphone placement is critically important to acoustic quality during live performances and recordings. Microphone placement alone contributes to around 20% of the overall sound while the person, instrument, setting, and microphone choice contributes to around 50%, 20%, and 10% of the overall sound respectively. In this post, we are going to explain why placement affects acoustic quality, and how to properly position the microphone in order to deliver best audio.
#1: Signal to Noise Ratio
Proper microphone placement provides optimal signal to noise ratio. Signal to noise ratio is the level of desired signal to the level of background noise. We recommend you choose a directional microphone to avoid unwanted noise from interfering with the quality of the audio. Directional microphones only pick up sounds from intended sounds sources placed in strategic positions, and offermaximum rejection of sounds coming surrounding areas.
# 2: Gain Before Feedback
Gain Before Feedback refers to how loud a sound system can be turned up before feedback occurs.Feedback is the annoying squeal soundcoming out of PA system pickedup by the microphone. Aligning floor monitors and side fills with the directional microphone’s angle of rejection allows for maximum gain before feedback.
#3: Acoustic Phase Cancellation
Acoustic phase cancellation occurs when two microphones are placed too close together and picks up sound from the same source. One microphone picks up the sounda little later than the other microphone because it’s placed a little further away. This often results in hollow sounds that lack depth. Repositioning the microphones based on 3:1 Rule of Microphone Placement will effectively avoid phase cancellation when recording with multiple microphones. Exercise the 3:1 rule by placing the second mic three times the distance from the first mic that the first microphone is from the source.
#4: The Sweet Spot
Lastly, proper microphone placement will help you find the "sweet spot". A sound source’s sweet spot is the ideal placement where the audio quality sounds best on the microphone. The audio from the sweet spot should has the most natural and balanced representation. It may require you to take the time to test, experiment and calibrate the sound in order to find the sweet spot.
The following are tips to help you find the sweet spot for omnidirectional mic, cardioid mic, and stereo pair:
Omnidirectional microphone: Cover one ear and listen with the other, move around the sound source until you find the spot that sounds best for you.
Cardioid microphone: Cover one ear and cup your hand behind the other. Move around the sound source until you find the spot that sounds best. The cupped ear simulates the way a directional mic picks up sound.
Stereo pair: Cup hands behind both ears, move around the sound source until you find the spot that sounds best.
The following are guidelines that work in almost any recording situation.It will help you achieve the best performance.
- Close-miking to avoid leakage into other mics, but give the mic some distance from the sound source in order to let the sound develop naturally.
- The best mic position cannot be predicted. The song, arrangement, player, instrument, recording environment, and signal path all have an impact on the final sound. Experiment with the mic placement since each recording situation is different.
- If the majority of the sound will come from the room, start getting sounds from those mics first, and then add any other mics that act as support.
- The 200 to 600Hz range is where the proximity effect often shows up.
- Use a variety of mics and different directional patterns to diminish the proximity effect buildup.
- Too much proximity effect can make vocals boomy or muddy. If proximity effect is not desired, moving the mic a few inches away from the sound source.