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Author Topic: Feedback through FOH last night.  (Read 14326 times)

frank kayser

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Re: Feedback through FOH last night.
« Reply #20 on: November 29, 2014, 07:45:59 pm »

Frank, I like to think of it as the compressor release adding extra gain (compared to when the vocalist is singing and the compressor's gain reduction kicks in). As you observe, the extra gain added when the compressor releases can be enough to cause feedback if the main PA makes it back into the mics.

Just a minor nitpick, though.... gain is gain and there's nothing special about adding makeup gain in the compressor, compared to adding it with the fader or mic preamp. Turn down the makeup gain 5 dB and push up the preamp or fader by the same amount and you're right back where you started.
Probably a better expression of what was going on.  Thanks, Jeff.
I think of make-up gain as "raising the signal floor" narrowing the whole signal level between the floor and the threshold, knee, and limiter.
frank
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g'bye, Dick Rees

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Re: Feedback through FOH last night.
« Reply #21 on: November 29, 2014, 08:02:24 pm »

System ring -out……..mmm……..sadly it was one of those gigs where we could'nt get in till late and we were going crazy trying to get set up on time. I had to roll with things bit and rely on my scene memory and quick room adjust…So much so that in the end the guys had a 60 sec sound check and that was it !! That didn't help things either !!

When you loaded your scene did it perhaps have any GEQ or PEQ settings on the mains L/R left over from the previous use or did you flatten them and start fresh?

You've probably already done this, but check p. 40, section 7.6 of the manual regarding RTA follows PFL.  I've started using this more. 
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Tim Padrick

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Re: Feedback through FOH last night.
« Reply #22 on: November 30, 2014, 03:30:20 am »

Kudos for finding a solution.

How many singers up front?  I've been in rooms where things were OK for the SL and SR singers, but the one in the middle was getting blasted by reflections.  On other occasions, the singers closest to the stacks were getting hit with reflections, yet the middle was just fine.  Without setup and soundcheck time, you need singers who can recognize what's happening, or you need to join them on stage during the show :-)
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Jay Barracato

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Re: Feedback through FOH last night.
« Reply #23 on: November 30, 2014, 11:11:06 am »

Was the feedback during the song or in the space between songs?

Often the culprit are the mics that are open but not hitting the compressor thresh hold.

Often the two knuckle ducker is the best solution.

Sent from my DROID RAZR HD using Tapatalk

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Jay Barracato

Tim McCulloch

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Re: Feedback through FOH last night.
« Reply #24 on: November 30, 2014, 02:18:21 pm »

So Debbie, what pitch was the feedback?  Low-middy or HF?  I'm thinking sympathetic vibration from a drum, excited by the vocals....  because frankly the other answers don't make physics sense if your make up gain was still under the level of feedback.
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Debbie Dunkley

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Re: Feedback through FOH last night.
« Reply #25 on: November 30, 2014, 03:55:29 pm »

When you loaded your scene did it perhaps have any GEQ or PEQ settings on the mains L/R left over from the previous use or did you flatten them and start fresh?

You've probably already done this, but check p. 40, section 7.6 of the manual regarding RTA follows PFL.  I've started using this more.

Although the scene recall carried the LR EQ, I leveled it and started from scratch before the band went on.

I have tried to use the RTA on the console but to be honest, not completely sure how to. I never seem to be able to isolate problem frequencies with it.
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Debbie Dunkley

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Re: Feedback through FOH last night.
« Reply #26 on: November 30, 2014, 03:56:07 pm »

Kudos for finding a solution.

How many singers up front?  I've been in rooms where things were OK for the SL and SR singers, but the one in the middle was getting blasted by reflections.  On other occasions, the singers closest to the stacks were getting hit with reflections, yet the middle was just fine.  Without setup and soundcheck time, you need singers who can recognize what's happening, or you need to join them on stage during the show :-)

It was the center singer that caused most of the feedback.
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Debbie Dunkley

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Re: Feedback through FOH last night.
« Reply #27 on: November 30, 2014, 03:58:04 pm »

Was the feedback during the song or in the space between songs?

Often the culprit are the mics that are open but not hitting the compressor thresh hold.

Often the two knuckle ducker is the best solution.

Sent from my DROID RAZR HD using Tapatalk

There seemed to be no real pattern to when the feedback occurred. If I could have isolated one mic and had the FB occur when open, at least I would have been able to pull down the fader at those times.
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g'bye, Dick Rees

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Re: Feedback through FOH last night.
« Reply #28 on: November 30, 2014, 04:09:26 pm »

There seemed to be no real pattern to when the feedback occurred. If I could have isolated one mic and had the FB occur when open, at least I would have been able to pull down the fader at those times.

For future reference, the metering page of the Qu-pad app will let you see which channel(s) are going over the top and the RTA below the meters will give a rough idea of the frequency, all on the same page/screen.
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Debbie Dunkley

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Re: Feedback through FOH last night.
« Reply #29 on: November 30, 2014, 04:19:04 pm »

So Debbie, what pitch was the feedback?  Low-middy or HF?  I'm thinking sympathetic vibration from a drum, excited by the vocals....  because frankly the other answers don't make physics sense if your make up gain was still under the level of feedback.

It sounded to me to be around 800-1000hz. However, the FB didn't disappear completely even when I adjusted the EQ at those frequencies (it did improve slightly). Only when I switched off the compression did it instantly disappear.

Regarding the make up gain on the comp, if switching the comp off caused no change in volume to the levels, doesn't that mean I had the make up gain set correctly?
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ProSoundWeb Community

Re: Feedback through FOH last night.
« Reply #29 on: November 30, 2014, 04:19:04 pm »


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