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Author Topic: graphic eq or feedback destroyer?  (Read 35387 times)

Greg_Cameron

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Re: graphic eq or feedback destroyer?
« Reply #20 on: February 05, 2012, 03:31:12 PM »

Looking at my measurements of the eq section of my 1604VLZ Pro I can confirm that the HPF causes a bump just above the cutoff frequency of about 0.1dB, and a wide dip above that of smaller amplitude.

I'd consider that negligible and not a cause for concern when a HPF is needed.

Greg
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Greg_Cameron

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Re: graphic eq or feedback destroyer?
« Reply #21 on: February 05, 2012, 03:39:03 PM »

I would rather not notch out 100-200 Hz range on the whole mix.  I'd like to eq my vocals on the bus and get more gbf in the mains.

I'll submit that if you're having feedback issues in that frequency range with vocal mics, notching out those frequencies on the house graph is not a bad thing. It's highly likely the room has issues with those frequencies and they need to be chopped for the entire mix to clean it up. That said, moving to aux fed subs is still a good move. Switching to mix desk with sweepable high pass filters on the channels strips would also be an excellent move. 80Hz high pass filters are woefully inadequate. So are 100Hz filters much of the time. Especially with a 12dB/octave roll-off. With vocal mics and 12dB per octave roll off, I'll often have a HPF frequency of 200Hz or even higher depending on the vocalist and vocal mic. One thing I'm really liking about moving to a digital mixer is the standard 24dB/octave roll off on the high pass filters. Very effective.

Greg
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michael sveda

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Re: graphic eq or feedback destroyer?
« Reply #22 on: February 05, 2012, 03:41:42 PM »

I don't see the church buying a new mixer soon.  I'd love he new presonus and someday I might have a deal on a Venice 320

I could use a 4 channel variable high pass filter rack unit
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g'bye, Dick Rees

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Re: graphic eq or feedback destroyer?
« Reply #23 on: February 05, 2012, 04:32:27 PM »

Turned off channel high pass filters on vox channels today and used channel eq.  Still had a bit of of feedback pop up on one song.  Had to take 100, 160 out of the main graph.  Going to try aux fed subs this week and see how that works.

Nothing wrong with dropping those two faders on the mains graphic.  As Greg points out, the system/room interaction likely is more sensitive in this area.  You're not "dumping" those frequencies, you're just balancing out the response within your particular acoustic environment.

I downloaded the manual for your console.  My condolences.  You're up against it for sonic surgery with this thing.  The EQ strips are pretty useless as configured.  Single sweepable mids aren't going to get you very far.

Another exercise in exodontia.
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michael sveda

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Re: graphic eq or feedback destroyer?
« Reply #24 on: February 05, 2012, 05:18:24 PM »

yeah, I miss using a Midas verona.....

But, you gotta do what you gotta do with what ya got.

aux fed subs up next.
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duane massey

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Re: graphic eq or feedback destroyer?
« Reply #25 on: February 05, 2012, 05:29:34 PM »

+1 on aux-fed subs. Will cost very little to try, and if it works there is one less piece of gear to worry about (unless you find the need to put an EQ on the sub chain).
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Derek Konop

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Re: graphic eq or feedback destroyer?
« Reply #26 on: February 05, 2012, 05:41:27 PM »

Derek,

No offense intended, but I beg to disagree with your analysis if only because it is too broad and the OP has not given any information which would make your take on it really valid.

Low end feedback can come from any mic, anywhere or can be a function of the physical relationship of several mics.

The first thing to do is to make sure the vocal mics are actually the culprits.  After that, use whatever channel strip EQ available to temper the LF response on the vox mics.  I commonly roll off the LF in the channel EQ as well as engaging the "rumble filter". Better to fix it at the individual mics than apply a blanket EQ band-aid downstream in the signal chain. 

I would also want to verify that the input gain on the mics is properly set and that the vocal mics are NOT being routed to the subs.

Edit:

I see that the vocals are being compressed in the sub-group.  The LF could well be occurring    when the comp lets loose.  Is there any make-up gain applied with the vocal comp???

Hey Dick,
I missed an important detail in the post right above mine. The fact that the feedback is not in the monitors, but in the mains. I kind of thought this was a 'What's the best way to get my monitors to stop screaming' thread.

I guess a less than effective channel strip EQ, an overlapping x-over point in the FOH cabs, and a 100hz-ish boomy room qualify as "Something else going on"? So I was kind of right!  ;D

Derek
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michael sveda

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Re: graphic eq or feedback destroyer?
« Reply #27 on: February 05, 2012, 05:47:16 PM »

I guess a less than effective channel strip EQ, an overlapping x-over point in the FOH cabs, and a 100hz-ish boomy room qualify as "Something else going on"? So I was kind of right!  ;D

Derek

Yes, I think I have a perfect storm around 100-160hz.  The strip mall room construction, hard walls, QSC's crossover, etc.

Do I need an EQ on the aux fed sub?  I plan on only feeding Kick and Bass gtr to start with. If we have keys they could go in subs.  Don't think i will send floor tom.

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Derek Konop

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Re: graphic eq or feedback destroyer?
« Reply #28 on: February 05, 2012, 05:56:17 PM »

Yes, I think I have a perfect storm around 100-160hz.  The strip mall room construction, hard walls, QSC's crossover, etc.

Do I need an EQ on the aux fed sub?  I plan on only feeding Kick and Bass gtr to start with. If we have keys they could go in subs.  Don't think i will send floor tom.

As Duane said above, it's not a necessity. But you may find that you want to.

Derek
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g'bye, Dick Rees

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Re: graphic eq or feedback destroyer?
« Reply #29 on: February 05, 2012, 07:02:31 PM »

Yes, I think I have a perfect storm around 100-160hz.  The strip mall room construction, hard walls, QSC's crossover, etc.

Do I need an EQ on the aux fed sub?  I plan on only feeding Kick and Bass gtr to start with. If we have keys they could go in subs.  Don't think i will send floor tom.

In one of my previous posts I asked what musical note the feedback has.  It should have a center frequency that you or someone with a musical ear can identify.  C, C sharp, D, etc..  Then you can simply use the pitch to frequency chart I linked for you to pin it down almost exactly and apply a narrow filter to counter the (apparent) room mode without having to resort to a broad cut with the graphic.......a cut which probably is more objectionable in theory than in practice.

 
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Re: graphic eq or feedback destroyer?
« Reply #29 on: February 05, 2012, 07:02:31 PM »


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