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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Mohit Palesha on May 20, 2012, 03:49:32 AM

Title: Microphone Feedback
Post by: Mohit Palesha on May 20, 2012, 03:49:32 AM
How people are getting lowest feedback from speakers during live program.
Tell me where to be more careful when selecting speakers.
Some say buy higher Fs speakers like 80hz for 12" speakers.

Guidance in the matter from fellow expert members.
Title: Re: Microphone Feedback
Post by: Charlie Zureki on May 20, 2012, 03:53:33 AM
How people are getting lowest feedback from speakers during live program.
Tell me where to be more careful when selecting speakers.
Some say buy higher Fs speakers like 80hz for 12" speakers.

Guidance in the matter from fellow expert members.


  Hello,

   Welcome.     The rules of this Forum dictate that REAL names be used.  Please go back and change your signature to your real name, and fellow Forum members will be glad to help you in any of your questions...
Title: Re: Microphone Feedback
Post by: Ivan Beaver on May 20, 2012, 08:42:25 AM
How people are getting lowest feedback from speakers during live program.
Tell me where to be more careful when selecting speakers.
Some say buy higher Fs speakers like 80hz for 12" speakers.

Guidance in the matter from fellow expert members.
It is not a simple answer.  It depends on a lot of factors-a good number are the HUMAN factor.

THe Human factors include how well the artist uses the mic-ie how loud do they sing-how close to the mouth-the position near the mouth (front-side-below etc).  Then there is how well is the monitor "rung out"-using eq to get rid of the "hot spots" that start the feedback. 

Then there is the position of the monitor (and its rejection pattern-they vary) and the rear of the mic.  You want the monitor to be in the position of most rejection of the mic.

Then there is hte whole "band" factor.  The louder it is on stage-the more bleed through there will be into the mics and the harder it is to get the vocal up to where you want them.

Then there is the quality of the monitor itself.  What is the polar pattern of the monitor?  How does that play into the polar pattern of the mic and the physical positioning (as stated above)?  What is the PHASE reponse of the monitor?  A monitor that has a smooth phase response is going to be able to get loduer than one that doesn't.

As you can see it is not a simple answer-and no ONE thing is going to get you what you seek.  It is a COMBINATION of all of them.

BTW-the FS of the speaker has nothing to do with gain before feedback.  But if it is really high-there will be less of a chance for low freq rumble-but a high pass filter will take care of that for you.

It is knowing your tools and how to use them-that really make a difference.  And using good tools.
Title: Re: Microphone Feedback
Post by: Rob Spence on May 20, 2012, 11:06:44 AM
And, just in case the OP is talking about feedback in the mains (he didn't specify), making sure the main speakers are positioned where their output isn't pointed near the mic and also they are pointed so reflections from walls or ceilings don't get to the mic.

One thing I have seen with monitors is reflections being a problem. For example, a lead singer right in front of the drums might get the monitor output reflecting off of the surface of the bass drum and then up to the mic. Especially when the performer steps aside and the mix is on the edge of feedback.

Another one is reflections off of a low ceiling, then to a hard back wall then back to the mic. All is well when the performer is right in front of the mic but when the move...
Title: Re: Microphone Feedback
Post by: Ivan Beaver on May 20, 2012, 12:14:47 PM
One thing I have seen with monitors is reflections being a problem.
And don't forget about cowboy hats and the reflection off of the brim.
Title: Re: Microphone Feedback
Post by: g'bye, Dick Rees on May 20, 2012, 01:07:18 PM
How people are getting lowest feedback from speakers during live program.
Tell me where to be more careful when selecting speakers.
Some say buy higher Fs speakers like 80hz for 12" speakers.

Guidance in the matter from fellow expert members.

Hello....

You need to first understand what feedback is.  As mentioned by other responders, it is a system phenomenon, not a function of any particular piece of equipment.  Feedback loops involve all/many of the components, so understanding how to adjust and/or place each piece of gear in the system is requisite.

The Yamaha Sound Reinforcement Handbook is very good for coming to terms with systems and how they work.  With some reading and effort (and asking a few questions), even a beginner can gain valuable knowledge. But it doesn't stop there.  The information in the book goes as far as you care to go with the engineering math, so it's a good long-term investment as well.  You don't have to be an engineer to use it, but if you're interested it can take you a long way.......from the beginning to the "top".
Title: Re: Microphone Feedback
Post by: John Roberts {JR} on May 20, 2012, 01:11:02 PM
Or do a search... the topic has been explored at great depth, many times here.

JR
Title: Re: Microphone Feedback
Post by: Jonathan Johnson on May 20, 2012, 08:57:42 PM
The only "microphone" I know of that is immune to feedback (except the snarky feedback this post is likely to generate):

(http://ecx.images-amazon.com/images/I/41A0S1pzv3L._SL500_AA300_.jpg)

http://www.amazon.com/10-Echo-Mike/dp/B000TZVIZC