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==Introduction==
If you have questions about this article, please see this  
If you have questions about this article, please see this  
<big> {{Community|link=https://twitter.com/ST_Muso/status/1391466144138100736|text=Microphone Feedback discussion}}</big>
{{Community|link=https://twitter.com/ST_Muso/status/1391466144138100736|text=Microphone Feedback discussion}}


== What is feedback and how does it occur? ==
== What is feedback and how does it occur? ==
Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.
Feedback occurs when the sound from the loudspeaker (or loudspeakers if a microphone is connected to more than one) is louder at the microphone than the sound of the voice.


This fundamental fact is shown in the figure below. Note that in the diagram an L1 system is shown but the same fundamental fact is true for ANY loudspeaker.
This fundamental fact is shown in the figure below. Note that in the diagram, an L1 system is shown, but the same fundamental fact is true for ANY loudspeaker.


[[Image:Feedback fig 1.jpg|400px|Microphone Feedback]]
[[Image:Feedback fig 1.jpg|400px|Microphone Feedback]]


If you understand this diagram, it is relatively easy to understand how changes in an amplification system and the room can contribute to either increasing or decreasing the likelihood of feedback.  
If you understand this diagram, it is relatively easy to understand how changes in an amplification system and the room can contribute to either increasing or decreasing the likelihood of feedback.  
           
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== Techniques For Reducing Feedback ==
== Techniques For Reducing Feedback ==
=== Gain Staging ===
=== Gain Staging ===
Your setup should always begin with good gain staging.
Your setup should always begin with good gain staging and with microphones, that starts with [[#Close Microphone Technique|great microphone technique]]. After that, you can consider [[##Gain_Staging_2|gain staging your equipment]].
 
==== {{T4S}}/{{T8S}} ====
{{ToneMatch Mixer Gain Staging and ToneMatch Preset}}
 
===== Set Up Your Source =====
Set your source at the maximum that it will be when performing.
* Microphone
:Sing directly into the microphone using close microphone technique (lips just brushing the windscreen). Sing as loudly as you will sing during your performance. You want to set the Trim to work at your maximum volume.
* Instrument
:Turn your input as high as it is likely to go during performance.
 
 
===== Trim Controls =====
The {{ToneMatch Mixer}} trim controls for Channels 1-4 (1-8 for the {{T8S}}) provide a significant gain increase when you reach the upper limit. This increase in gain is normal operation.
 
Most sources like typical microphones and piezo pickup systems can provide enough level without the need to add significant gain from the trim control. Certain sources like passive acoustic guitar pickups require additional gain and in these cases it can be necessary to set the trim level to the upper range of the control. When the trim control is set this high you may notice the gain change. This is normal operation. If you want to run the trim control at lower settings we recommend using a preamp or simple stomp box level booster.
 
 
The trim for Aux input channels 5/6 (9/10 for the {{T8S}}) do not exhibit the same behavior as the trim controls for Channels 1-4 (1-8 for the {{T8S}}).  The Aux inputs are designed for line level sources and do not have the same gain staging as channels 5/6 (9/10 for the {{T8S}}).
 
 
==== {{T1}} ====
{{:T1 ToneMatch® Audio Engine / Gain Staging a Microphone}}
 
 
* If you are using the {{T1}}, the principles are the same as shown on the video: simply substitute the [[T1_ToneMatch%C2%AE_Audio_Engine#Set_Input_Trim|trim]] on the {{T1r}} for the trim on the Classic or Model I. {{T1 icon}}
 
Your first adjustment for any input to your {{T1}} is the Trim setting. The exact position of the Trim will vary depending on signal strength of your input source. The correct setting for any particular source may be different from your other sources.
 
[[Image:T1TrimPots.png|T1® Trim Pots]]  
 
Take two minutes to watch this video by clicking on the picture below.
 
{{Get Plugged In Microphone}}
* If you are using an {{Classic}} or {{Model I}} follow the instructions exactly as shown in the video.
 
===== Set Up Your Source =====
Set your source at the maximum that it will be when performing.
* Microphone
:Sing directly into the microphone using close microphone technique (lips just brushing the windscreen). Sing as loudly as you will sing during your performance. You want to set the Trim to work at your maximum volume.
* Instrument
:Turn your input as high as it is likely to go during performance.
 
===== Set Trim Controls =====
Turn the Trim setting up until the Trim Light is solid green with occasional flickers of yellow. Use the Trim lights as your guide. (The exact position of the Trim knob is not important).
 
[[Image:TrimlightsOK.gif]]
 
If you see flickers of red (below), turn the Trim down. You are definitely nearing or in compression. Turn the Trim down until there are no red flickers.
 
[[Image:TrimlightsNo.gif]]
 
Bill-at-Bose <ref>[http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/9821050644?r=7191052284#7191052284 Bill-at-Bose Talks about Gain Staging in the Bose® Musicians Community Message Boards]</ref> talks about setting the gain on a {{T1}}.
 
:One difference in gain staging the T1 and the Classic is that the T1 has a three-stage trim LED. It lights up green when signal is present, yellow when you are getting pretty loud (8 to 10 dB of headroom left), and red when you dangerously close to or at full scale.
 
:In a way, the yellow trim on the T1 is similar to how you treat the red on the Classic. Some yellow during peaks is good on the T1, just like some red on the Classic is good.
 
:If the T1 trim is going red, you should back off, you are definitely nearing or in compression.
 
:A really helpful feature on the T1 is to go to the Prefs/Output Level menu, and see where you are relative to maximum output.
 
==== T1 Trim Pots ====


{{:T1 ToneMatch® Audio Engine / Trim Pots}}


=== Close Microphone Technique ===
=== Close Microphone Technique ===
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=== Directional Microphones ===
=== Directional Microphones ===
==== Principles ====
==== Principles ====
Use a directional microphone. [[Microphone Directionality#Supercardioid_/_Hypercardioid|Hypercardioid]] is better than [[Microphone Directionality#Cardioid|cardioid]], which is better than [[Microphone Directionality#Omnidirectional Microphone|omnidirectional]]. All sound waves impinging on the microphone from a direction other than the intended signal is "noise" and will lower the threshold of feedback.


Directional microphones "collect" less sound from directions other than what they're supposed to amplify (the voice, or an instrument) and hence are less likely to feed back.
Choose a '''directional microphone''' to maximize gain‑before‑feedback. A [[Microphone Directionality#Supercardioid_/_Hypercardioid|Hypercardioid/Supercardioid]] pattern provides the strongest focus on the intended source, followed by [[Microphone Directionality#Cardioid|Cardioid]], with [[Microphone Directionality#Omnidirectional Microphone|Omnidirectional]] offering the widest pickup (the least desirable in most live sound applications).
 
Directional microphones excel because they emphasize the desired sound—such as a voice or instrument—while naturally reducing sound arriving from other directions. This focused pickup helps maintain clarity and increases the system’s resistance to feedback.


In addition, most directional microphones have a strong behavior called [[Proximity Effect|proximity effect]]. This is the strong buildup of bass and low-mid response as the source (say the voice) to microphone distance decreases. For microphones intended to sound natural when the voice is very close -- say one of a number of popular stage vocal microphones -- what this means is that low-to-middle frequencies from sources at a distance, including loudspeakers being used to amplify the voice, are largely rejected by the microphone. This is a real plus in terms of avoiding microphone feedback.
Most directional microphones also offer a helpful characteristic known as the [[Proximity Effect|proximity effect]]. As the source moves closer to the microphone, low and low‑mid frequencies become fuller and more pronounced. Microphones designed for close‑up vocal use take advantage of this: they deliver a natural tone at close range while reducing low‑to‑mid frequency content from distant sources, including nearby loudspeakers. This selective emphasis further improves feedback performance.
 
Omnidirectional microphones, by contrast, maintain a consistent tone regardless of distance. This can be ideal in studio environments where uniformity is the goal. On stage, however, their equal sensitivity in all directions means they capture more ambient sound and offer less natural rejection of low‑to‑mid frequency energy. As a result, they provide less gain‑before‑feedback than directional designs.


Conversely, an omnidirectional microphone (equal sensitivity to sound coming from any direction) has no proximity effect. This is an advantage often in the studio where the engineer wants consistent tone regardless of distance. But it's a disadvantage on stage in terms of feedback. An omnidirectional mic collects more sound that's not the target, and because it has no proximity effect is more susceptible to feedback at low-to-mid frequencies than a directional mic.
====Omnidirectional and Unidirectional Microphones====
====Omnidirectional and Unidirectional Microphones====
{{:Microphone Polar Pattern}}
{{:Microphone Polar Pattern}}
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=== Monitor Placement ===
=== Monitor Placement ===
If you are using stage monitors, be sure to place them so they are directing sound at the area of the microphone that rejects the most sound.
{{Monitor Placement}}
 
Note from [https://www.shure.es/musicos/descubre/contenido-didactico/microphone-basics-transducers-polar-patterns-frequency-response Shure.com]
:Other variants on the unidirectional polar pattern include supercardioid and hypercardioid options. Both patterns offer narrower front pickup angles than the cardioid – 115 degrees for the supercardioid and 105 degrees for the hypercardioid – alongside greater rejection of ambient sound. Additionally, while the cardioid is least sensitive at the rear (180 degrees off-axis), the supercardioid is least sensitive at 125 degrees and the hypercardioid at 110 degrees. When placed properly they can provide more 'focused' pickup than the cardioid pattern, but they also have less rejection at the rear. If you're using either of these polar patterns on stage with wedge monitors, it's important make sure you avoid placing the wedges directly behind the mic in this instance. Instead, place them either side at the mics least sensitive angle.
 
[[File:Microphone Polar Patterns and Monitor Placement.jpg|400px]]


=== Open Microphones ===
=== Open Microphones ===
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=== Distance Between Microphones ===
=== Distance Between Microphones ===
Another (low priority) design guide-line could be to keep open microphones as far apart as possible. Neighboring systems with open microphones can mutually decrease [[Gain Before Feedback|gain before feedback]].
Another (low priority) design guide-line could be to keep open microphones as far apart as possible. Neighboring systems with open microphones can mutually decrease [[Gain Before Feedback|gain before feedback]].


== Techniques specific to the {{L1 family}} ==
== Techniques specific to the {{L1 family}} ==
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For this reason, whenever possible, use a microphone with a ToneMatch preset.
For this reason, whenever possible, use a microphone with a ToneMatch preset.
=== Gain Staging ===
==== L1 Pro and S1 Pro/Pro+ ====
When you sing or play at the loudest you will perform, the channel light should be solid green. Occasional flickers of red are okay. But if you see solid red, turn down the volume. Important: Use [[#Close Microphone Technique|close-microphone technique]]. The farther you are from the microphone, the greater the likelihood of feedback.
==== T4S/T8S Gain Staging ====
{{T4S/T8S Gain Staging}}
==== {{T1}} ====
{{:T1 ToneMatch® Audio Engine / Gain Staging a Microphone}}
* If you are using the {{T1}}, the principles are the same as shown on the video: simply substitute the [[T1_ToneMatch%C2%AE_Audio_Engine#Set_Input_Trim|trim]] on the {{T1r}} for the trim on the Classic or Model I. {{T1 icon}}
Your first adjustment for any input to your {{T1}} is the Trim setting. The exact position of the Trim will vary depending on signal strength of your input source. The correct setting for any particular source may be different from your other sources.
[[Image:T1TrimPots.png|T1® Trim Pots]]
Take two minutes to watch this video by clicking on the picture below.
{{Get Plugged In Microphone}}
* If you are using an {{Classic}} or {{Model I}} follow the instructions exactly as shown in the video. 
===== Set Up Your Source =====
Set your source at the maximum that it will be when performing.
* Microphone
:Sing directly into the microphone using close microphone technique (lips just brushing the windscreen). Sing as loudly as you will sing during your performance. You want to set the Trim to work at your maximum volume.
* Instrument
:Turn your input as high as it is likely to go during performance.
===== Set Trim Controls =====
Turn the Trim setting up until the Trim Light is solid green with occasional flickers of yellow. Use the Trim lights as your guide. (The exact position of the Trim knob is not important).
[[Image:TrimlightsOK.gif]]
If you see flickers of red (below), turn the Trim down. You are definitely nearing or in compression. Turn the Trim down until there are no red flickers.
[[Image:TrimlightsNo.gif]]
Bill-at-Bose <ref>[http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/9821050644?r=7191052284#7191052284 Bill-at-Bose Talks about Gain Staging in the Bose® Musicians Community Message Boards]</ref> talks about setting the gain on a {{T1}}.
:One difference in gain staging the T1 and the Classic is that the T1 has a three-stage trim LED. It lights up green when signal is present, yellow when you are getting pretty loud (8 to 10 dB of headroom left), and red when you dangerously close to or at full scale.
:In a way, the yellow trim on the T1 is similar to how you treat the red on the Classic. Some yellow during peaks is good on the T1, just like some red on the Classic is good.
:If the T1 trim is going red, you should back off, you are definitely nearing or in compression.
:A really helpful feature on the T1 is to go to the Prefs/Output Level menu, and see where you are relative to maximum output.
==== ToneMatch Mixer Trim Controls ====
{{:T1 ToneMatch® Audio Engine / Trim Pots}}


=== Tilt the Mic Up ===
=== Tilt the Mic Up ===
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== Other References ==
== Other References ==
Here's a quick link to other articles about <categorytree mode="pages" hideroot="off" namespaces="Main">Feedback</categorytree>
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* [http://www.shure.com/stellent/groups/public/@gms_gmi_web_ug/documents/web_resource/us_pro_mics_for_music_sound_ea.pdf Microphone Techniques for Live Sound Reinforcement] Shure Educational Publication 2006 39 pages - pdf format
* [http://www.shure.com/stellent/groups/public/@gms_gmi_web_ug/documents/web_resource/us_pro_mics_for_music_sound_ea.pdf Microphone Techniques for Live Sound Reinforcement] Shure Educational Publication 2006 39 pages - pdf format
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