paano ma eliminate/lessen feedback?

[acdsee]

help mga sir..... may  PA system po ako for personal use in our small church community gatherings, may live bands din na tumutogtog, my problem is paano mababawasan ang feedback? lalo na pag medyo nilalakasan mo na... minsan pag wala pa mga tao at pag soundcheck namin ok naman, pero once kumapal na tao, may feedback na na lumalabas,,,is it advisable na bumili pa ako ng anti-feedback devise? at kung effective naman talaga ang ganung devise? how about tamang positioning ng mga speakers?  ang venue po namin nag-iiba-iba....minsan sa open space or minsan sa multipurpose/function halls to give you the idea. saka bakit nung simpleng mixer at power amps lang yung set-up ko di gaano nag-fefeedback, nang magdagdag na kami for example compressor, equalizer, etc...frequent na ang feedbacking? may effect po ba yon?  tnx

[mikep]

....minsan sa open space or minsan sa multipurpose/function halls to give you the idea. saka bakit nung simpleng mixer at power amps lang yung set-up ko di gaano nag-fefeedback, nang magdagdag na kami for example compressor, equalizer, etc...frequent na ang feedbacking? may effect po ba yon? 

Watch out on the settings of your compressors.  Also, since you have a 1/3 octave EQ, you can cut on offending frequencies.  It helps if you have an analyzer to to this.  Automatic feedback eliminators would normally affect the naturalness of your sound.  Also, your Front of House speakers should always be placed in such a way that they are 1 or 2 meters away from the mics, their backs facing each other.

FWIW

[Agent_So]

sir how frequency analyzer works? may indication ba dun what frequency ang ngfefeedback? para i ste mo ang eq mo?  if ever,what brand, and how much are this? ngkakaproblema rin ako minsan sa feedback.. miski sa open area..



thanks

[starfugger]

you could sweep thru the frequency spectrum with a parametric eq and find the offending frequency, and cut on that.  feedback is usually a sine wave (correct me if im wrong) so it's pretty easy to eliminate.  mr mike actually showed us ways to tune your pa system kaso nalimot ko na yung steps.

[TheHunter]

After placing the right location of speakers, placement of monitor speakers and right gain, setup your band with mics, cabs, etc... (other guys here can tell you more) here's what I normally do:

1. Set you master volume to 0 dB
2. Set your gain knob to zero in each channel of mixer console
3. Slide your 1st track volume fader to the maximum then turn you gain up slowly until you reach just
    before feedback, then turn the gain down a little bit around 5 dB or one scale.
4. Repeat step 3 for the rest of your channels.
5. Mark each gain knob as your "ceiling" (meaning this your maximum gain you can set before
    feedback)

With this technique you are sure you will not have or minimize the feedback. Try this and thanks to me later. 

[mikep]

sir how frequency analyzer works? may indication ba dun what frequency ang ngfefeedback? para i ste mo ang eq mo?  if ever,what brand, and how much are this? ngkakaproblema rin ako minsan sa feedback.. miski sa open area..

See the Hunter's post.  That could be a good start. That's right, you ring your monitors and your FOH and see the "feedbacking" frequencies.  Then you cut them using your EQ.  As for analyzers, call Audiophile.  They have some simple models you can get to see offending frequencies.  I have a small handheld analyzer for feedback from Goldline.  It just tells you what frequencies are acting up by lighting up brightly.  Then, you can adjust your 1/3 EQ.  This is not available locally though.  There is a Phonic model you can get also.  The local distributor I believe has a stock.

FWIW

[bindoy]

peace to all ganda nitong thread na to...nararanasan din namin ito sa community namin...basa basa basa...hehehe

[abyssinianson]

help mga sir..... may  PA system po ako for personal use in our small church community gatherings, may live bands din na tumutogtog, my problem is paano mababawasan ang feedback? lalo na pag medyo nilalakasan mo na... minsan pag wala pa mga tao at pag soundcheck namin ok naman, pero once kumapal na tao, may feedback na na lumalabas,,,is it advisable na bumili pa ako ng anti-feedback devise? at kung effective naman talaga ang ganung devise? how about tamang positioning ng mga speakers?  ang venue po namin nag-iiba-iba....minsan sa open space or minsan sa multipurpose/function halls to give you the idea. saka bakit nung simpleng mixer at power amps lang yung set-up ko di gaano nag-fefeedback, nang magdagdag na kami for example compressor, equalizer, etc...frequent na ang feedbacking? may effect po ba yon?  tnx

notch filtering is your friend. also check out the quality/ integrity of your cables. shorts in the cable can cause hum and feedback. some pieces of gear have a ground lift feature to cure this but it isn't a safe thing to have engaged all the time, especially with pro-audio gear.

[acdsee]

thanks po mga sir!!! hindi ako nagkamali sa pag post ng thred na to!   

[mbenipayo]

i dont recomend using feedback eliminators, they usually affect the overall sound, not just killing the feedback

I'd also sugget using a parametric EQ, it much easier to hit the offensive frequency right on the head with that.  parametric EQs are so affordable now compared to years ago.

right speaker placement, if possible, is the best point to start, coz' once you have bad speaker placement that causes feedback, you'd be spending the rest of the day to "remedy", not cure the problem.

[Agent_So]

guys, idea naman ng price ng analyzer, na mura lang.. that will do the job.. brand na rin. thanks..

[skunkyfunk]

Here's a simple way... INVERT THE PHASE OF THE WEDGE MONITORS...

[BAMF]

And suffer a power drop and a thin, phased-out sound.

Here's a simple way... INVERT THE PHASE OF THE WEDGE MONITORS...

[BAMF]

Lessee...try eliminating one by one the possible sources of feedback. (not mutually exclusive with the other good advice though). Does the feedback occur with the mikes on ? Does it occur only when the band is playing ? Baligtad nga e. Feedback should be reduced once there are people in the venue because they'll act as dampeners.

I've had my share of that kinda shyt. My guitar was microphonic and it ruined our show. Anyway...

You'll have to be a little more specific what kind of PA system you're using. If you use monitor speakers that face the band, you will have to position the mikes perpendicularly to the plane of the monitor. And etc etc etc but it's hard to give specifics if there are no specifics from your end as well

help mga sir..... may  PA system po ako for personal use in our small church community gatherings, may live bands din na tumutogtog, my problem is paano mababawasan ang feedback? lalo na pag medyo nilalakasan mo na... minsan pag wala pa mga tao at pag soundcheck namin ok naman, pero once kumapal na tao, may feedback na na lumalabas,,,is it advisable na bumili pa ako ng anti-feedback devise? at kung effective naman talaga ang ganung devise? how about tamang positioning ng mga speakers?  ang venue po namin nag-iiba-iba....minsan sa open space or minsan sa multipurpose/function halls to give you the idea. saka bakit nung simpleng mixer at power amps lang yung set-up ko di gaano nag-fefeedback, nang magdagdag na kami for example compressor, equalizer, etc...frequent na ang feedbacking? may effect po ba yon?  tnx

[skunkyfunk]

And suffer a power drop and a thin, phased-out sound.

Here's a simple way... INVERT THE PHASE OF THE WEDGE MONITORS...

In theory when you have two signals out of phase, they cancel each other,  but in a PA concept, it is the feedback that gets amplified due to in-phase signals of the monitors and the mic.  Hence you must reverse the phase of the wedge monitors.  I learned this from another pro audio forum.

Why not try it for yourself?

[BAMF]

Yes we did when I was still apprenticing with my brother (who's the pro audio engineer between him and me) and not just the feedback that was in phase got cancelled out. Including the bass response.

There are better ways.

And suffer a power drop and a thin, phased-out sound.

Here's a simple way... INVERT THE PHASE OF THE WEDGE MONITORS...

In theory when you have two signals out of phase, they cancel each other,  but in a PA concept, it is the feedback that gets amplified due to in-phase signals of the monitors and the mic.  Hence you must reverse the phase of the wedge monitors.  I learned this from another pro audio forum.

Why not try it for yourself?

[mbenipayo]

How we did it years ago with big concerts, especially those that had large choirs was this.  Invert the phase of 1 or 2 mics in a group of mics.  say, in the choir, 2 of 6, for the front vocals, 1 of 3.  This is where those phase invert switch in mid to large consoles come in handy.  if you do not have that feature, make a phase invert connector.  its like a very short mic cable with pin 2 & 3 inverted on one XLR.

Phase cancellation is prominent in the lower freq. region, not too much at the top.  The other thing is, you are not giving the mic exactly the signals anyway so there would be very few points where a frequency would cancel out.

I don't subscribe to the idea of inverting the monitoring, logic being, if you invert the whole lot, it would still be, in essence,  in-phase (all moving in the same direction) It may be out-of-phase with reference to the Front-Of-House and that all together would have an adverse effect  on you sound….and yet not really addressing the core problem of controlling feedback.

1)   Check speaker placement, is there a mic that is in front or near proximity to the main speakers?
2)   Is the feedback coming from the monitors or from the FOH?
3)   Are the right mics being used?
4)   There might be too many mics open at any 1 time.

in any case, this might be a bit crude but if you feel you have done everything  and the feedback is still there, you could experiment.   While the service is going on and there is feedback, flick the mute switch one after the other (going off-on) if the feedback disapears on a certain channel(s), then that is it.  I suggest the MUTE switch as opposed to riding the faders up & down because if you are using Pre-fader on your wedges, it won’t get affected whereas the MUTE kills the channel. 

Just pick the service with the least people so that when they start noticing, only a few heads with a frown  will turn to you…..hahahah