Monday’s post on feedback prevention prompted a good question from Ryan, a reader. He said,
“…there was one phrase that jumped out at me. Specifically, ‘Regarding floor monitors, vocalists should be very close to their floor monitor.’ I wanted to ask what the reasoning is behind this? I would think the further away the singer is, the more the sound is diffused; ergo, feedback is reduced.”
One hard part of live audio production is…monitor usage. A musician needs monitors for hearing sounds to be in key and in time. The sound tech needs the musician to sing into a microphone using the right technique so they can get a solid sound for mixing. The audience / congregation needs to hear a great house sound. Let’s look at how these relate.
Looking specifically at a fictional vocal singer, we have five factors to take into account:
- The microphone they use.
- How they use the microphone.
- The monitor they use.
- How they use the monitor.
- What they hear in the monitor.
1. The microphone they use
Microphones come in a variety of types with a variety of frequency responses but let’s focus on their polar pattern. The polar pattern is the area around the microphone capsule and how a particular microphone picks up sound around it. For example, an omni-directional polar pattern picks up sound equally all around the microphone. A cardioid (see image) picks up sound in the front and sides but not behind the microphone.
Omni’s could easily create feedback because they are picking up sound “behind the mic” that’s coming straight from the monitor.
Let’s give the vocalist a common, albeit aging, Shure SM58 microphone. This is a dynamic vocal microphone with a cardioid polar pattern. As an aside, find out the polar patterns of your microphones. They’ll either have a small picture of it on the microphone or you can check out the manuals. Most microphone spec’s are available online.
2. How they use the microphone
Vocal microphones need to be held right up to a singer’s mouth, tilted at about a 45’ish degree angle up to their mouth. This way, you can get the clearest sound without getting other stage noises in the mix. While you can’t get total sound isolation in the live environment, by having the sound source so close to the microphone, you can get pretty darn close. Let’s say our vocalist is properly holding the microphone.
3. The monitor they use
Focusing on the source of this question and the original topic of feedback, two monitor types are to be noted; floor monitors, also called floor wedges, and spot monitors. Spot monitors are smaller and are usually placed on a stand.
The vocalist, and any musician, sees the monitor as a necessity. If they can’t hear other singers, they can’t harmonize. If they can’t hear the right rhythm instrument, they can’t sing in time. It’s for this reason musicians might spend a lot of time asking for the right monitor volume and mix.
Let’s put our vocalist in front of a floor monitor.
4. How they use the monitor
Our vocalist needs to be standing on-axis to the floor wedge. The moment they are off-axis, that is to say they are outside of the sound cone radiating from the monitor speaker, then they are hearing significantly less volume. But how close do they need to stand?
This leads us into the topic of stage volume. Stage volume is the amount of sound on a stage. Sources of stage volume would be acoustic instruments, singers, drum kits, and monitors. These are all different sounds that can be heard on stage that don’t emanate from the house speakers.
Our vocalist needs to stand as close as possible to their floor wedge because of two reasons;
- They need to clearly hear their monitor
- You need to keep the stage volume to a minimum.
Stage volume, when excessive, destroys the sound in the room because, at that point, the stage volume is exceeding the house volume. Excessive stage volume also makes monitor mixing a nightmare.
5. What they hear in the monitor
Without going into detail on monitor mixes, I’ll hit a few highlights as it would relate to our vocalist. First, they need to hear voices for harmonizing and a rhythm instrument or two for timing. They DON’T need every sound in their mix. Second, they need to hear all of these in the right relationship to each other. Think volume.
Only now can the question be answered…
“‘Regarding floor monitors, vocalists should be very close to their floor monitor.’ I wanted to ask what the reasoning is behind this?”
Bringing this all together and remembering we are scoping this around feedback.
Feedback, in the case of monitors, is produced when a sound is looped between the microphone and the monitor to the point where the volume looping between the two begins to significantly increase. It’s usually a specific frequency but let’s skip the details for now.
So why do we want our vocalist up close to their monitor?
The biggest point that I can make is that when you properly set the gain for that vocalist’s microphone, they keep it up to their lips, and you have ONLY enough volume needed coming out of the monitor, then feedback won’t be a problem.
Where feedback does come into play is usually when;
- The microphone is too hot and picks up more monitor than necessary. This goes back to setting the proper channel gain.
- The monitor is too loud and the microphone is looping the sound. Going back to our stage volume discussion, we don’t want to negatively impact the house volume or produce too much volume from one monitor that it affects others on the stage.
This all leads back to the original article and the three ways to easily prevent feedback;
- Place microphones in the right relationships to monitors. Close enough the singer hears the volume they need when they are standing on-axis to the monitor speaker cone.
- Teach musicians to use the proper vocal microphone technique. The moment a vocalist drops the microphone from their mouth to their chest or their stomach, a significantly greater amount of gain is required which can produce feedback and will pick up more sounds on the stage. And dropping the microphone to their side will certainly throw everything into a loop because of the close proximity from the monitor the microphone. They need to keep the microphone up to their mouth or step away if they drop it to their side.
- Use the proper gain setting technique. The channel gain setting is foundational for all your work. It gives you the amount of channel signal you need and is the best aid in preventing feedback. A channel that’s too hot will cause just as many problems as a channel that’s not loud enough.
The Take Away
You have to keep several areas in check when producing live audio. These areas include stage volume, feedback, and monitor usage. To Ryan’s question, the farther away the vocalist from the monitor, the more monitor volume and thus stage volume. But when you place the vocalist in the right relationship with the monitor and they use proper the microphone technique, then they hear everything they need, you get the right sound signal you need, and the congregation hears the sound coming from the house speakers, not from the stage.
*Tip: If you are having problems with feedback when the monitors are set and the musicians are properly using the microphones, check the type of polar pattern of the microphone. You are likely using an omni-directional microphone wherein a cardioid microphone would be better suited for your situation.
Looking for all the details behind what makes microphones unique? Check out this guide to microphones with a focus on vocal microphones.