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Author Topic: gain issues in live set up not sure how to fix..please help  (Read 21260 times)

Jeff Young

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Re: gain issues in live set up not sure how to fix..please help
« Reply #30 on: November 21, 2012, 09:42:06 pm »

Where did you come by this piece of misinformation? it is absolutely not true.

The factors that lead to feedback include poor speaker placement, poor microphone technique, unrealistic expectations for monitor volume, unrealistic expectations for PA volume, eq, and dynamics processing, in roughly that order.

How much you can turn up the PA doesn't depend on how far the knob is turned, it is determined by when feedback starts. The first place to start eliminating feedback is with the above list in pretty much that order. Position and aim the PA speakers so they cover the audience, but minimize the amount of sound that gets back on stage. Use microphones that have some rejection to the sides, and do not "cup" the mic as this makes them omnidirectional. Listen from out in the audience area to how loud the vocals are. Since you have aimed the speakers away from the stage already you have no real idea of how loud it is in the audience area. You will not be able to sing softly into the mic and have it be Slayer coming out of the PA. If the feedback is consistently happening at one or two frequencies you may be able to reduce those frequencies with some eq. This may give you better gain before feedback, or it may make the mics sound crappy, it's a tradeoff. Once you are able to get the vocals loud enough to mix with the band's stage sound you can think about dynamics control, but remember that it wiil never reduce feedback, only increase the likelihood of it.

On a small stage there will be limits to how you can set up the PA. If the vocals are the limiting factor, and can't keep up with the band's stage sound, it is time to think about reducing the stage sound so you can do a better show. A show volume that is less than you want is probably better than a crappy mix with the instruments overpowering the PA.

Mac

have seen a few postings on here alone saying that the power amp should be set at 0db...on my amp this is all the way up. This is why I refer to "all the way up"... wasn't speaking in volume terms. At this moment due to earlier info I gleaned from YouTube a while back I have this mixer set in such a way that the power amp is unable to go above -14db before feeding back at an extreme level of sound. I am no where near a sound engineer but if this was normal they wouldn't be producing them with the other -12 to 0 db increments...unless of course they enjoy making us think that enough adjustments might one day get us a sound we will never get. Due to the things I have read on here all I can really do for now is show up to practice this weekend move a few things around, remove the drummer from the Pa, tell the singer that he doesn't have to make love to the mic but needs to get at least a bit friendlier with it. Change a few settings on the PA....and see what happens.   


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Jeff Young

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Re: gain issues in live set up not sure how to fix..please help
« Reply #31 on: November 21, 2012, 09:44:50 pm »

Stick around.  You'll get the help you need......sooner or later. 

But you'll need to accept the fact that your concept of how things work is just in the formative stage.  You've made some statements that imply a misunderstanding of how things work.  If I or someone else call you on it, don't take it personally.  The object is to get things stated clearly (both the problems and the solutions) and to accept all our individual approaches, limitations and talents......whatever they are.

Keep at it.
sorry man the way you worded that seemed a bit too short.
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g'bye, Dick Rees

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Re: gain issues in live set up not sure how to fix..please help
« Reply #32 on: November 21, 2012, 11:43:16 pm »

At this moment due to earlier info I gleaned from YouTube a while back I have this mixer set in such a way that the power amp is unable to go above -14db before feeding back at an extreme level of sound. 

Here's "Rule #1" regarding feedback:

Loudest sound at the mic wins.

Translation:

If the mic "hears" the sound from the speakers as the loudest sound present, feedback will happen.
It's a system phenomenon, not a function of where the knobs and sliders are set.

As Mac pointed out, if the feedback happens at a certain few frequencies, these can be addressed with a good graphic (or parametric) EQ.  Do you have an EQ for your system?
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Jeff Young

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Re: gain issues in live set up not sure how to fix..please help
« Reply #33 on: November 22, 2012, 09:36:30 am »

Here's "Rule #1" regarding feedback:

Loudest sound at the mic wins.

Translation:

If the mic "hears" the sound from the speakers as the loudest sound present, feedback will happen.
It's a system phenomenon, not a function of where the knobs and sliders are set.

As Mac pointed out, if the feedback happens at a certain few frequencies, these can be addressed with a good graphic (or parametric) EQ.  Do you have an EQ for your system?
I do have an old Carvin 32 band EQ with a few shelves and a boost but nothing that locates any troubled frequencies. And its kinda scratchy due to the sliders being dirty. But it does work for the moment. Haven't wired it to the PA as of yet though. A few people have suggested a particular Behringer EQ with feedback finding capability. But my experience is that newer Behringer stuff is garbage. At-least their pedals are, not sure if this translates into their rack mount equipment or not.
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Brad Weber

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Re: gain issues in live set up not sure how to fix..please help
« Reply #34 on: November 22, 2012, 09:37:04 am »

At this moment due to earlier info I gleaned from YouTube a while back I have this mixer set in such a way that the power amp is unable to go above -14db before feeding back at an extreme level of sound. I am no where near a sound engineer but if this was normal they wouldn't be producing them with the other -12 to 0 db increments...unless of course they enjoy making us think that enough adjustments might one day get us a sound we will never get.
You probably don't always drive with the accelerator to the floor but I bet it's nice to be able to do so when you need it.
 
The input sensitivity for the GX3, which is the input signal level that generates full output, is around +3.8dBu, thus any incoming signal level above that needs to be attenuated.  On your mixer the maximum output is probably +24dBu or greater.  24dBu - 3.8dBu = 20.2dBu.  So your mixer can likely output a signal 20dB or so greater than the signal level that creates full output for the amplifier.  There are reasons for that but it is why it is common for many mixers and other electronics to require 20dB or so of attenuation at the amplifier inputs in order to have proper gain structure.  And that is addressing purely gain structure, which has nothing to do with gain before feedback.
 
Due to the things I have read on here all I can really do for now is show up to practice this weekend move a few things around, remove the drummer from the Pa, tell the singer that he doesn't have to make love to the mic but needs to get at least a bit friendlier with it. Change a few settings on the PA....and see what happens.
A good start but you could also do some things you could do in advance.  For example, research the patterns for your microphones and speakers and try to get a better understanding of how they may interact with one another.  Practice identifying frequencies so that you may have a better idea of what frequencies are feeding back.  And study why you may want to have the "Low Cut" enabled on the EQ for mic channels.
« Last Edit: November 23, 2012, 09:45:36 pm by Brad Weber »
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Tim McCulloch

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Re: gain issues in live set up not sure how to fix..please help
« Reply #35 on: November 22, 2012, 09:42:23 am »

I do have an old Carvin 32 band EQ with a few shelves and a boost but nothing that locates any troubled frequencies. And its kinda scratchy due to the sliders being dirty. But it does work for the moment. Haven't wired it to the PA as of yet though. A few people have suggested a particular Behringer EQ with feedback finding capability. But my experience is that newer Behringer stuff is garbage. At-least their pedals are, not sure if this translates into their rack mount equipment or not.

"Feedback finding" in most of its implementations is basically an LED that lights up for whatever frequency band has the most signal.  That may or may not represent feedback depending on how you're attempting to use it.

Training the gray matter computer between your ears is a much more effective way, but it takes a little bit of time to learn.  Do a web search for "simple feedback trainer."
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Jeff Young

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Re: gain issues in live set up not sure how to fix..please help
« Reply #36 on: November 22, 2012, 11:48:52 am »

"Feedback finding" in most of its implementations is basically an LED that lights up for whatever frequency band has the most signal.  That may or may not represent feedback depending on how you're attempting to use it.

Training the gray matter computer between your ears is a much more effective way, but it takes a little bit of time to learn.  Do a web search for "simple feedback trainer."

Loaded that trainer and it does look useful.
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Ned Ward

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gain issues in live set up not sure how to fix..please help
« Reply #37 on: November 22, 2012, 11:55:11 am »

If you do get a new or used EQ, peavey and ART both had models with lights to show the feedback frequency. Not automatic, but the Behringer "feedback destroyers" don't work - I bought one on eBay for $35 and I still felt ripped off after using it.

Worthwhile addition.

Other things to check:
Speakers should be forward of mic position; otherwise, you risk having their sound going back into the mics. While it can be done with speakers behind you, I'd recommend starting with them in front of the mics. If the singer is moving around, know that if he moves in front of the speakers at this level you'll get feedback.

Also ensure your speakers are at the right height - good info on this site on the proper height and how to do it.

No one is suggesting Slayer at lounge levels, but if your PA only goes so loud, you'll have to turn down everything else to hear the vocals.
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Re: gain issues in live set up not sure how to fix..please help
« Reply #38 on: November 22, 2012, 12:06:51 pm »

I do have an old Carvin 32 band EQ with a few shelves and a boost but nothing that locates any troubled frequencies. And its kinda scratchy due to the sliders being dirty. But it does work for the moment. Haven't wired it to the PA as of yet though. A few people have suggested a particular Behringer EQ with feedback finding capability. But my experience is that newer Behringer stuff is garbage. At-least their pedals are, not sure if this translates into their rack mount equipment or not.

Jeff...

I've written the following procedure so many times that I should really put it in a .doc so I can just paste it in.  There are some YouTube videos, but I find something wrong or "fuzzy" in every one I've looked at and so do not link to them.  But there are quite a few. 

To locate problem frequencies in your setup and attenuate them with a graphic EQ:

1.  Hook up your system as usual, then set your input gain for your mics as usual.  Meters should show peaks of not more than +3 with the strongest signal applied at the input.  Power amp should be full up.  Graphic EQ should be patched between the console output and the power amp.

2.  Set your microphone channel faders to a bit above 0.

3.  Now raise the Master fader until you hear the first "hot" frequency start to ring, then back off just a tad.

4.  Starting from the low (left) side of your graphic, proceed to boost and return to 0 each of the bands one at a time until you encounter the first one to excite the system into ringing.  Then apply a cut on that frequency.  You'll know how deep to make your cut by how quickly and intensely the system "blows up".  If it's immediate and strong, try cutting 6dB.  If it's slow and light, then cut just a couple of dB.

5.  Lather, rinse, repeat until you've gone through all 31 bands.  If you're cutting a lot of frequencies, then something is drastically wrong with your setup in regards to speaker positioning.

6.  Return your channel faders to the bottom, raise your Master fader to -5 or so, then proceed to build your mix.  If you find you're raising your channel faders above 0 to get what you need, then back them off and raise the Master fader and continue.


I run my systems in mono so I only have to do this with a single channel of EQ.  Once you've learned how to do it, you can run "stereo" if you want.  The procedure for "ringing out" the system will be the same, just taking a bit longer to deal with two channels.

This is a simple over-view of how to do a basic EQ.  There are other tricks and caveats, but for now this will help you get more out of your system before it feeds back.

Get yourself a nice, clean graphic with long-throw adjustments (avoid the single rack-space models).  It'll allow everything else to function at a higher level and is arguably the best money you can spend at the moment.  The "feedback finder" models are somewhat of a gimmick  as Tim mentioned.  The machine can only identify which bands are "hotter", not which bands are actually feeding back.

Oh......one more thing.

Once you've gone through the procedure with all the mics open, try raising your system volume until it just starts ringing,  then, one at a time, either mute or drop the fader on each mic in turn to see which one is the first offender.  You can then perform further, finer adjustments by using the channel strip EQ to lessen that particular input's response to the hot frequency.

The DBX graphics are very affordable and serviceable.  I've used the 2231's for many years and they'll do the job for you.  They also make a cheaper model with the same filters and without the limiter of the 2231 and it should be just as good for you.

Best of luck.     
 
« Last Edit: November 22, 2012, 12:11:54 pm by dick rees »
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Jeff Young

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Re: gain issues in live set up not sure how to fix..please help
« Reply #39 on: November 22, 2012, 10:10:38 pm »

Jeff...

I've written the following procedure so many times that I should really put it in a .doc so I can just paste it in.  There are some YouTube videos, but I find something wrong or "fuzzy" in every one I've looked at and so do not link to them.  But there are quite a few. 

To locate problem frequencies in your setup and attenuate them with a graphic EQ:

1.  Hook up your system as usual, then set your input gain for your mics as usual.  Meters should show peaks of not more than +3 with the strongest signal applied at the input.  Power amp should be full up.  Graphic EQ should be patched between the console output and the power amp.

2.  Set your microphone channel faders to a bit above 0.

3.  Now raise the Master fader until you hear the first "hot" frequency start to ring, then back off just a tad.

4.  Starting from the low (left) side of your graphic, proceed to boost and return to 0 each of the bands one at a time until you encounter the first one to excite the system into ringing.  Then apply a cut on that frequency.  You'll know how deep to make your cut by how quickly and intensely the system "blows up".  If it's immediate and strong, try cutting 6dB.  If it's slow and light, then cut just a couple of dB.

5.  Lather, rinse, repeat until you've gone through all 31 bands.  If you're cutting a lot of frequencies, then something is drastically wrong with your setup in regards to speaker positioning.

6.  Return your channel faders to the bottom, raise your Master fader to -5 or so, then proceed to build your mix.  If you find you're raising your channel faders above 0 to get what you need, then back them off and raise the Master fader and continue.


I run my systems in mono so I only have to do this with a single channel of EQ.  Once you've learned how to do it, you can run "stereo" if you want.  The procedure for "ringing out" the system will be the same, just taking a bit longer to deal with two channels.

This is a simple over-view of how to do a basic EQ.  There are other tricks and caveats, but for now this will help you get more out of your system before it feeds back.

Get yourself a nice, clean graphic with long-throw adjustments (avoid the single rack-space models).  It'll allow everything else to function at a higher level and is arguably the best money you can spend at the moment.  The "feedback finder" models are somewhat of a gimmick  as Tim mentioned.  The machine can only identify which bands are "hotter", not which bands are actually feeding back.

Oh......one more thing.

Once you've gone through the procedure with all the mics open, try raising your system volume until it just starts ringing,  then, one at a time, either mute or drop the fader on each mic in turn to see which one is the first offender.  You can then perform further, finer adjustments by using the channel strip EQ to lessen that particular input's response to the hot frequency.

The DBX graphics are very affordable and serviceable.  I've used the 2231's for many years and they'll do the job for you.  They also make a cheaper model with the same filters and without the limiter of the 2231 and it should be just as good for you.

Best of luck.     
 
yes you probably do need to save that to a pdf or something...thanks now go rest your fingers.
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ProSoundWeb Community

Re: gain issues in live set up not sure how to fix..please help
« Reply #39 on: November 22, 2012, 10:10:38 pm »


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