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Author Topic: Where to patch feedback eliminator?  (Read 7360 times)

Dave Rigter

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Where to patch feedback eliminator?
« on: December 14, 2011, 10:40:03 pm »

Hi all,

Need a bit of help.
I've acquired a not so expensive feedback eliminator to go into our Chapel.
Only thing is I'm sure where to patch it.
The manual says patch it into either a group and assign all mics there, or into an insert point.

Currently it's patched like this:

Main outs of SoundCraft EPM to FBQ.
FBQ outs, direct to inputs of L & R Bose L1 Portable Line Array.
Line out of L1's go to Line inputs of 2nd pair of L1's (halfway down chapel)

My concern was also that the FBQ may not receive enough level to analyze the feedback properly.
Thus I turned down the powered L1's to 25% (previously set @ 50%), so I could turn up the gain at the mixer to get a proper level @ the FBQ and incidentally at the meters.

My aim is to allow the mixer to be operated by Nuns and retirees (not ideal I know, but its what I got).

I want the FBQ to safeguard against ppl turning everything up full.
But I also need enough level so when ppl with brains put the levels @ 0 instead of +10 you can still hear.

Do I patch the FBQ at the insert points over the main mix?
If so, am I inserting the output of the FBQ there, or do the inserts "break the chain" before the mix outputs and send the "mix" to the FBQ?

I can see I actually have 2 problems.
*Unsure of where how to patch the FBQ
*Incorrect gain structure - unsure of how high to have amp settings in correlation with HA Gain....

Sorry, I'm sure it's obvious, but I have really confused myself here and would appreciate some help!

TIA!
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Marcus Wilson

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Re: Where to patch feedback eliminator?
« Reply #1 on: December 14, 2011, 11:14:47 pm »

Hi all,

Need a bit of help.
I've acquired a not so expensive feedback eliminator to go into our Chapel.
Only thing is I'm sure where to patch it.
The manual says patch it into either a group and assign all mics there, or into an insert point.

Currently it's patched like this:

Main outs of SoundCraft EPM to FBQ.
FBQ outs, direct to inputs of L & R Bose L1 Portable Line Array.
Line out of L1's go to Line inputs of 2nd pair of L1's (halfway down chapel)

My concern was also that the FBQ may not receive enough level to analyze the feedback properly.
Thus I turned down the powered L1's to 25% (previously set @ 50%), so I could turn up the gain at the mixer to get a proper level @ the FBQ and incidentally at the meters.

My aim is to allow the mixer to be operated by Nuns and retirees (not ideal I know, but its what I got).

I want the FBQ to safeguard against ppl turning everything up full.
But I also need enough level so when ppl with brains put the levels @ 0 instead of +10 you can still hear.

Do I patch the FBQ at the insert points over the main mix?
If so, am I inserting the output of the FBQ there, or do the inserts "break the chain" before the mix outputs and send the "mix" to the FBQ?

I can see I actually have 2 problems.
*Unsure of where how to patch the FBQ
*Incorrect gain structure - unsure of how high to have amp settings in correlation with HA Gain....

Sorry, I'm sure it's obvious, but I have really confused myself here and would appreciate some help!

TIA!

Hi Dave,

A lot of stuff there.

You have the FBQ in a suitable place.

I feel you may be confused about how it operates.  The unit looks for continuous, single frequency events and pops in an equaliser section to cut at that frequency.

It's not sensing level as such.  It may require the level to be over a particular level to be able to operate properly, but would be quite low, say -30dBu.  Your system should probably be well over that, without altering the power amp inputs.  In other words, if the output meter on your EPM is indicating any level at all, you should have enough for the FBQ to do it's job.  The main thing is that you don't overload it by turning the amps down too far and drive heaps of level from the desk to compensate.

The FBQ is not a limiter, so it will not stop the system going too loud, it will only catch feedback events as they occur.  If someone turns everything up full and there's lots of feedback issues, then the FBQ will run out of filters and you will still get feedback (and horrible sound)!

Basically it will do 50% of what an engineer can do with a decent equaliser, but it doesn't have a real brain, so if there's an idiot on the desk it will be powerless to fix it!!!

The mix insert points are a good place to put it.  They 'break the chain' just before the master faders. I'm not sure whether the inserts or where you have it would be best, try and see, but they are both valid.

The instructions about the group insert is so you get the FBQ only affecting the microphones and not playback or other sources.  Sometimes the eq changes can be quite severe and badly affect music or recorded material playback.

By the way, one of the best things you could do is delay the signal to the second set of Bose.   It will drastically increase the intelligibility in the rear of the room.

rgds, M.
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rgds, M.

Owned a regional sound company for 30 years.
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g'bye, Dick Rees

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Re: Where to patch feedback eliminator?
« Reply #2 on: December 14, 2011, 11:22:39 pm »

Never mind........
« Last Edit: December 14, 2011, 11:24:52 pm by dick rees »
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Dave Rigter

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Re: Where to patch feedback eliminator?
« Reply #3 on: December 15, 2011, 12:34:10 am »

Hi Dave,

A lot of stuff there.

You have the FBQ in a suitable place.

I feel you may be confused about how it operates.  The unit looks for continuous, single frequency events and pops in an equaliser section to cut at that frequency.

It's not sensing level as such.  It may require the level to be over a particular level to be able to operate properly, but would be quite low, say -30dBu.  Your system should probably be well over that, without altering the power amp inputs.  In other words, if the output meter on your EPM is indicating any level at all, you should have enough for the FBQ to do it's job.  The main thing is that you don't overload it by turning the amps down too far and drive heaps of level from the desk to compensate.

The FBQ is not a limiter, so it will not stop the system going too loud, it will only catch feedback events as they occur.  If someone turns everything up full and there's lots of feedback issues, then the FBQ will run out of filters and you will still get feedback (and horrible sound)!

Basically it will do 50% of what an engineer can do with a decent equaliser, but it doesn't have a real brain, so if there's an idiot on the desk it will be powerless to fix it!!!

The mix insert points are a good place to put it.  They 'break the chain' just before the master faders. I'm not sure whether the inserts or where you have it would be best, try and see, but they are both valid.

The instructions about the group insert is so you get the FBQ only affecting the microphones and not playback or other sources.  Sometimes the eq changes can be quite severe and badly affect music or recorded material playback.

By the way, one of the best things you could do is delay the signal to the second set of Bose.   It will drastically increase the intelligibility in the rear of the room.

rgds, M.

Thanks Marcus.
Yes I was concerned that a lack of level would not allow the FBQ to do what it should.
I will try placing it at the mix inserts points and see what I get from there.

Cheers for the advice!
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Jay Barracato

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Re: Where to patch feedback eliminator?
« Reply #4 on: December 15, 2011, 02:00:25 pm »

Never mind........

I would patch it in between the 15 band graphic and the sonic maximizer.


And then I would make sure nothing is hooked up to any of it.
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Jay Barracato

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Re: Where to patch feedback eliminator?
« Reply #5 on: December 15, 2011, 02:04:02 pm »

I would patch it in between the 15 band graphic and the sonic maximizer.


And then I would make sure nothing is hooked up to any of it.

I was going to post a picture of a train wreck, but I've been getting cited for excessive sarcasm lately.

I do not consider the FBX unit to be of much use in this or any such situation no matter how you patch it.  Proper system setup and control should take care of things.  I'd be more concerned about using another set of ultra-wide dispersion speakers as un-delayed reinforcement. 

Now where can I find a picture of mud????
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info@travelingmonkeysound.com

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Re: Where to patch feedback eliminator?
« Reply #6 on: December 15, 2011, 03:17:09 pm »

I would patch it in between the 15 band graphic and the sonic maximizer.


And then I would make sure nothing is hooked up to any of it.

Jay is 100% correct if this situation affords real sound engineer support... which is sort of the point of this forum... perhaps this thread is more for the HOW area?

But Dave I think you should be up in arms about under qualified people being at the helm... If you can't get someone who can find a feedback frequency and address the issue... good luck. Whenever that system is running the public image of your venue, and probably your reputation is going to come into question. And if feedback is a common problem, groups will look for other places to meet.

I also think that Dave is in a realistic world where inexperienced persons may be left in charge of equipment. And if this is going to happen - for audience health concerns isn't it better that they do deploy a feedback device? 

If you do have to use the FBX then you want a different mixer. Get one with an insert on a bus that you only assign microphones through. Put the FBX there, and a 31 band equalizer while you're at it - and train those nuns how to use it. Then as Jay said, unplug the FBX.
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Jonathan Johnson

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Re: Where to patch feedback eliminator?
« Reply #7 on: December 15, 2011, 04:36:11 pm »

So... how does a feedback destroyer know the difference between feedback (a "continuous, single frequency event" that may be produced by interaction between loudspeakers and microphones) and an extended musical note (a "continuous, single frequency event" that may be produced by some instruments)?
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Dave Rigter

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Re: Where to patch feedback eliminator?
« Reply #8 on: December 15, 2011, 05:20:40 pm »


Thanks Nils,
Good call on moving the post to the HOW forum. Fair call.
and yes, I'm not the best FOH engineer but I'm doing the best with what I've got.
This is a school chapel setup, used at all sorts of weird times so independence from me is really what I'm aiming for.

I'll see what I can do about installing a graphic.  Makes a lot of sense.

As far as gain structure goes, I'm still a little confused.
Should I be adjusting the system so that level at the desk is healthy (around -5 or 0 at the meters), then set the amps to an appropriate level?
Or, set the amps to 80% and adjust levels at the mixer accordingly?


Jay is 100% correct if this situation affords real sound engineer support... which is sort of the point of this forum... perhaps this thread is more for the HOW area?

But Dave I think you should be up in arms about under qualified people being at the helm... If you can't get someone who can find a feedback frequency and address the issue... good luck. Whenever that system is running the public image of your venue, and probably your reputation is going to come into question. And if feedback is a common problem, groups will look for other places to meet.

I also think that Dave is in a realistic world where inexperienced persons may be left in charge of equipment. And if this is going to happen - for audience health concerns isn't it better that they do deploy a feedback device? 

If you do have to use the FBX then you want a different mixer. Get one with an insert on a bus that you only assign microphones through. Put the FBX there, and a 31 band equalizer while you're at it - and train those nuns how to use it. Then as Jay said, unplug the FBX.
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Jean-Pierre Coetzee

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Re: Where to patch feedback eliminator?
« Reply #9 on: December 15, 2011, 06:02:07 pm »


Should I be adjusting the system so that level at the desk is healthy (around -5 or 0 at the meters), then set the amps to an appropriate level?
^
This has been discussed in depth before.

Leave the anti-feedback unit somewhere where some non God-fearing person can find a new home for it. I understand the need but rather just teach the nuns how not to destroy the system(churches all over have achieved bad, not destructive sound; so can you).
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Re: Where to patch feedback eliminator?
« Reply #9 on: December 15, 2011, 06:02:07 pm »


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