Best mic for gain-before-feedback?

[Robert Linkroum]

Dear MadKayaker,
In your Battle of the Bands event, if different bands bring some or all of their own gear, the following is a stellar solution:
In addition to, or instead of, the "slash and burn" EQ solutions listed here, try first using a high quality Compressor / Limiter such as the DBX 1066 - about $ 500 USD (has XLR and quarter-inch In and Out connections with lots of status indicators to verify the different operational settings).
Music and vocals that have potential for wide variations in dynamic range will have momentary peaks that can send a sound reinforcement system into howling feedback.
The use of a Limiter to put a brick wall on the peaks will go far in reducing the peaks that can trigger feedback and place a ceiling on the overall sound for the seated audience.
This sound ceiling will be esecially helpful if a audio feed is going to a video camera.
If you choose to EQ the system, use an Automatic Feedback Supressor such as the Behringer Shark - about $100 USD (again XLR and quarter-inch In and Outs with multiple helpful indicators). Both the use of the Limiter and the Feedback Supressor work well in a unknown room and performance situation.
when correctly used, this audio trickery will work and do it in a invisible manor.
A quick check with the bands, may find that one of them has these devices already.
The Auto Feedback Supressor does the work of a deep notch Parametric EQ, but just does if faster and better.
The audience will just remember a fun time without a hint of nasty feedback.
-Robert Linkroum
Belmont Shore, California
("The Come As You Are Section" of Long Beach, CA)
310 951 9985

 

[FMEng]

This thread is six years old. Not sure why it needs a response now. Controlling levels and peaks with a compressor/limiter will not reduce the chance for feedback. If that were true, it would be harder to drive a system into feedback with mics sitting on a quiet stage. It isn't hard to demonstrate that the same amount of gain will result in feedback regardless of the sound levels. Compression is an important tool, but using it actually makes it harder to control feedback, because the compressor is effectively turning up the gain when the loudness of the source is getting softer. It is like having an invisible hand pushing up the fader.

 

[Floobydust]

Audix OM7 is a winner for my band gigs.

Very narrow pattern, so the performer has to be right on it.

 

[museav]

In your Battle of the Bands event, if different bands bring some or all of their own gear, the following is a stellar solution:
In addition to, or instead of, the "slash and burn" EQ solutions listed here, try first using a high quality Compressor / Limiter such as the DBX 1066 - about $ 500 USD (has XLR and quarter-inch In and Out connections with lots of status indicators to verify the different operational settings).
Music and vocals that have potential for wide variations in dynamic range will have momentary peaks that can send a sound reinforcement system into howling feedback.
The use of a Limiter to put a brick wall on the peaks will go far in reducing the peaks that can trigger feedback and place a ceiling on the overall sound for the seated audience.
This sound ceiling will be esecially helpful if a audio feed is going to a video camera.
If you choose to EQ the system, use an Automatic Feedback Supressor such as the Behringer Shark - about $100 USD (again XLR and quarter-inch In and Outs with multiple helpful indicators). Both the use of the Limiter and the Feedback Supressor work well in a unknown room and performance situation.
when correctly used, this audio trickery will work and do it in a invisible manor.
A quick check with the bands, may find that one of them has these devices already.
The Auto Feedback Supressor does the work of a deep notch Parametric EQ, but just does if faster and better.
The audience will just remember a fun time without a hint of nasty feedback.

Perhaps we should start with whether you are advocating inserting this gear on individual channels, subgroups or the overall mix as those could give quite different results.

Feedback is not a factor of dynamics or absolute level, it is a factor of having an electroacoustical loop gain of greater than 1. The typical situation that causes feedback is a microphone seeing a level from the sound system that is greater than the original source level at that same microphone, thus the sound 'loops' through the system buidling in level with each pass. As that can be a factor of many relative phase related issues, feedback also tends to be very frequency specific. However, whether the source level at a microphone is 120dB and the level from the system at the same mic 125dB or the source level is 40dB and the level from the system 45dB, there is the same 5dB above unity gain and thus the same susceptibility to feedback. Dynamics and absolute level are not really relevant unless they somehow also cause a change in the associated loop gain.

So a limiter may be able to limit the feedback level to whatever threshold level you have set but it won't avoid or elminate feedback. In addition, you have to watch how you use 'makeup' gain on a comp/limiter. If you compress or limit the peaks of the signal by some amount and then apply a makeup gain equal to that reduction you end up with the same peak levels but a greater average level. That may be good for getting a source up out of the mix but it may actually make a system more susceptible to feedback. So lots of good reasons to use a comp/limiter but avoiding feedback is not one of them.

An Automatic Feedback Suppressor usually works best if used on individual inputs, if assigned to the overall mix can affect the quality of the sound. I find that an AFS is too often used as a 'band aid' to treat feedback that occurs rather than trying to avoid feedback in the first place. An AFS may make it a great 'backup' to have in place for those unexpected situtations but you probably still want to maximize gain before feedback as much as you can without the Automatic Feedback Suppressor.