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gordon k



Joined: 26/05/05
Posts: 23
Automatic Feedback Suppressors
      #834035 - 17/05/10 06:54 PM
I'm wondering if anyone has any recommendations for a good automatic feedback suppressor.

I'm looking for something that can autodetect feedback frequencies and put notch filters on them as they pop up, to take them down just below the 0dB.

This is for creative/compositional use: I don't want to eliminate feedback completely, but to create feedback signatures with lots of different peaks, rather than just one single frequency that overwhelms everything. So I'm looking for something which will give me control over various aspects of the process, e.g. the Q of the filters, the rate at which they kick in etc.

In short, tweakability is what I'm after - audiophile fidelity is not that vital, since it's the feedback process itself that I'm interested in.

Hardware and software options both of interest...


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Paul Wright



Joined: 16/02/06
Posts: 17
Loc: Derbyshire, UK
Re: Automatic Feedback Suppressors new [Re: gordon k]
      #834055 - 17/05/10 09:01 PM
Sabine make some superb feedback suppressors. However, I'm not sure they would be appropriate for your creative/compositional needs as they do a damn fine job of eliminating feedback! Might be worth a look none the less...

Regards,

Paul


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gordon k



Joined: 26/05/05
Posts: 23
Re: Automatic Feedback Suppressors new [Re: gordon k]
      #834184 - 18/05/10 11:29 AM
Cheers Paul -

I've had a read up about the Sabines online. Very impressive - but I think what you're saying might be true. They seem very clever at discriminating between feedback signatures and "signal" - analysing harmonic patterns and narrowband gain increases etc. I probably need something slightly less smart, that will let an inefficient human tell it how to deploy its filters.

Edited by gordon k (18/05/10 11:31 AM)


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seablade



Joined: 21/11/04
Posts: 4014
Re: Automatic Feedback Suppressors new [Re: gordon k]
      #834190 - 18/05/10 11:51 AM
Quote gordon k:

Cheers Paul -

I've had a read up about the Sabines online. Very impressive - but I think what you're saying might be true. They seem very clever at discriminating between feedback signatures and "signal" - analysing harmonic patterns and narrowband gain increases etc. I probably need something slightly less smart, that will let an inefficient human tell it how to deploy its filters.




Perhaps you just want a parametric EQ?

Seablade


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gordon k



Joined: 26/05/05
Posts: 23
Re: Automatic Feedback Suppressors new [Re: gordon k]
      #834205 - 18/05/10 12:39 PM
Yes, I'm using some parametrics and a graphic/spectrum analyser at the moment.

But because I'm deliberately generating feedback, most of my time gets taken up killing excessive frequencies on the graphic. So I want some kind of automation to gently rein in the extreme stuff, & let me spend all my time sculpting the sound with the parametrics...


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Nathan



Joined: 13/09/04
Posts: 1893
Loc: lincolnshire government experi...
Re: Automatic Feedback Suppressors new [Re: gordon k]
      #834289 - 18/05/10 04:37 PM
Just trying to remember if you can freeze the EQ filters on any of the Sabines or Behringers. How many channels of parametric EQ do you have?

I've run my Sabines through Room Equalisation Wizard before, to see what they have implemented. Maybe do that and then copy the settings across to your parametrics.

Another way would be use a spectrum analyser to monitor the precise frequency of any feedback that comes up, and then manually notch out just enough of those frequencies to quell feedback on something like one of the Behringer digital multi-parametrics (or several in series). REW will do as the spectrum analyser (http://www.proaudioshack.com/forums/8-rew-room-eq-wizard)

By manually taking out just enough gain at each freq, and using your mic to listen (and watch) for resurgent frequencies (freq hanging-on, nearly feeding back), you should be able to bring several to ring at once.

It will be an iterative process, and I'm not sure quite why you want to do this (as a live SE, feedback makes me twitch), but it should work.

Bear in mind that as you get closer to multi-frequency feedback, even the act of walking across your "soundstage" will affect the acoustic environment enough to set something off!

>

--------------------
planet nine
lincoln, uk.


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ROLO46



Joined: 29/11/07
Posts: 1204
Loc: Cotswolds
Re: Automatic Feedback Suppressors new [Re: gordon k]
      #834317 - 18/05/10 06:04 PM
A good mixer will show howl as ch overload led
Whiz the parametric around for fun effect
45 YRS too late though

--------------------
I am the Walrus.


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gordon k



Joined: 26/05/05
Posts: 23
Re: Automatic Feedback Suppressors new [Re: Nathan]
      #834325 - 18/05/10 07:00 PM
Quote Nathan:

Just trying to remember if you can freeze the EQ filters on any of the Sabines or Behringers. How many channels of parametric EQ do you have?



I'm currently using four channels of parametric, plus various filters on my analogue gear.

I've found someone selling one of the Behringer DSPs near where I live (I'm pretty sure you can freeze the filters on them).
So I think I'll get that and a copy of REW - thanks for the link! - and experiment.

This is all taking place in the studio at the moment (heh - not quite sure how this ended up in the Live Sound forum) so there is a lot of room for experiment, and mistakes are not a problem. But I am hoping to be able to do this sort of thing live too. I guess the idea might be to set up some basic filters in the venue before performance, lock them down, and then have some free-floating ones to deal with whatever crops up. The way I imagine it, most of the extreme feedback frequencies will be down to the room acoustic + mic + PA, rather than whatever else is happening sonically during the performance? Is that a fair assumption?

(It's surprising, incidentally, how pleasing all of this sounds. I'm not a fulltime noise terrorist, and these big waves of controlled feedback & reverb that are getting generated are curiously soothing... )


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Sheriton



Joined: 27/01/03
Posts: 1555
Loc: Leicester, UK
Re: Automatic Feedback Suppressors new [Re: ROLO46]
      #834426 - 19/05/10 08:02 AM
Quote ROLO46:

A good mixer will show howl as ch overload led





If the feedback is loud enough to run the channel in to clipping, I'd be long gone from the venue!

--------------------
There's nothing we can't face... Except for bunnies


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ROLO46



Joined: 29/11/07
Posts: 1204
Loc: Cotswolds
Re: Automatic Feedback Suppressors new [Re: Sheriton]
      #834587 - 19/05/10 07:17 PM
Quote Sheriton:

Quote ROLO46:

A good mixer will show howl as ch overload led





If the feedback is loud enough to run the channel in to clipping, I'd be long gone from the venue!




Not a live Hendrix fan then?

Yamaha have a pre clip howl indicator

--------------------
I am the Walrus.


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