microphone feedback

[pac162 0]

hi all !

 

would like some tips for avoiding microphone feedback http://www.dj-forum.co.uk/html/emoticons/smile.gif

 

as i'll be providing karaoke this is probably going to be a big issue for me !

 

i'll have a total of 4 mics and have the problem that the singers will need to hear the music without getting any feedback.

 

i realise i could use a wedge monitor on the floor but wondered if there was any other ways of reducing the chance of feedback. could the singers stand in line with the speakers rather than directly in front...would this help?

 

my speakers are also on stands....does this help provide the best sound in general? if they were on the floor would this help with feedback ??

 

i use a behringer multicom dynamics processor for the mics too...is there anything clever i can do with this to help...presumable the peak limiting or compression could stop the 'squealing' http://www.dj-forum.co.uk/html/emoticons/biggrin.gif

finally would a feedback destoyer be a good investment...has anybody used or can recommend one ?

 

thanks in advance for all your help http://www.dj-forum.co.uk/html/emoticons/beer.gif

 

 

 

 

 

[Gary 0]

What you need is to send the music to the monitors, without the mic signals. It is the mic "hearing itself" which creates mic feedback.

 

If your mixer has a Booth or Record Out, check the manual...as some mixers dont send the mic signal to those outputs. If this output IS mic-free then use that output to drive the monitor speakers (via an amp) for the wailers...sorry, singers.

 

Alternatively, get your mic-free signal directly from the back of the dvd/cdg player before it goes into your mixer, and again provide that output to the singers.

 

Only the speakers pointing at the audience will contain both music and mic signals.

 

[MadGutts 0]

Floor monitors would be the best option. However as Gary has pointed out, the mixer has got to be able to support this.

A feedback destroyer of some description will also help... but these take some setting up.

 

The best setup for karaoke is:

 

Two main speakers away from the singers, pointing towards the crowd.

The TV, and performers mics behind the line of the speakers.

The Player and mics into individual channels of the mixer - gives you more control.

Then the audio from the player fed to both main and PFL on the mixer

The Main output from the mixer to the main amp and speakers

The PFL output to the stage monitors.

 

This is the ideal way of setting up... http://www.dj-forum.co.uk/html/emoticons/biggrin.gif

 

But if you mixer doesn't have a PFL facility for you to send to another amp, you can make lead from the headphone socket on you mixer and using the Cue, you can send the cd output to another amp... Not ideal, but it would work.

 

Also... don't boost the mics too muh, the singer will tend to shout over the mics, so get them to sing loudly... The ladies can be a little more shy and hold the mic too far from them... this you will find out !!! http://www.dj-forum.co.uk/html/emoticons/biggrin.gif

 

If you use a radio mic for the karaoke a feedback destroyer is a must. I use 2 feedback destroyer on my karaoke, because me and my collegue sing as well. So we have 2 radio mics going through the main mixer via a feedback destroyer on an effect send, then back out of the mixer into the main feedback and deq, etc...

This way can go out into the crown and sign, then pick an audience member to sing !!!

 

It works well and we enjoy ourselves too! http://www.dj-forum.co.uk/html/emoticons/thumbup.gif http://www.dj-forum.co.uk/html/emoticons/thumbup.gif

[RobbieD 0]

Hi Pac!

 

The most important factor in avoiding feedback is using the right microphone. Cheaper mics with their less controlled responses tend to feedback more. Something like an SM58 is a good compromise between quality, and price (considering you need several and punters may not treat them well).

 

Singers should not be in front of the speakers. A mic like the SM58 picks up most sound from in front, less from the sides, and very little from behind (the direction that the cable goes off in). (Sorry if I am making this too simple.) Therefore if the singer is in front of the speakers the mic will pick up lots of sound from the speakers and feedback more.

 

For the same reason, if you use a monitor, place it on the floor just behind the mic stand (ie. opposite side to the singer), in line with the mic's handle (where the mic has least pick up).

 

Also having the mic's on stands to keep them in this position, rather than the singers waving them around will help.

 

Generally live acts have a separate mix for the monitors. This could have the mics at a lower level than the mix in the main speakers. No mics at all in the monitors can make it hard for the singer to hear themselves, unless the monitors are kept at a low level.

 

The monitor mix is about a compromise between it sounding like the singer wants, and not getting feedback, where as the main mix is about it sounding good to the audience. For instance, the monitor mix typically doesn't contain any echo on vocals, as echo tends to increase feedback, and makes it harder for the singer to hear themselves. Where as echo on the vocals in the main (audience) mix makes singers sound better.

 

Avoid compression, as this tends to increase feedback, although a limiter may be useful to save your speakers from singers screaming or dropping the mic. If your Behringer unit has a gate, then setting this to cut out when they are not singing may help reduce the possibility of feedback.

 

I would only use a feedback destroyer if all else failed.

[pac162 0]

thanks for your help guys !

 

i am using a sm58 radio mic and 3 wired sm58's...i dont currently have a stage monitor.

 

it sounds like ideally i'll need to get a feedback destroyer for the radio mic...in case i decide to go walkabout with the crowd, and also a stage monitor for singers to be able to hear themselves.

 

can anybody suggest a good feedback destoyer...the behringer one looks quite reasonable and accepts 2 mics inputs i think ??

 

my mixer's (the vocopro kj-800 i think) booth output includes the mics..so that would mean id have to run the monitor though the headphone socket with the cue. However...if i wanted some vocals on the monitor to help the singer...could a get a powered monitor with an eq and maybe use the eq to reduce the chance of feedback genereated from the monitor?? (sorry if im gettin myself confused) http://www.dj-forum.co.uk/html/emoticons/wacko.gif

 

finally http://www.dj-forum.co.uk/html/emoticons/smile.gif if i got a feedback destroyer..then how would i wire the unit up with my existing mixer and behringer multicom processor...at the mo each of the 4 mic channels on the mixer just uses its effect send return to go to each of the 4 inputs on the processor.

 

thanks again

paul.

[HopDJ 0]

Our mixer has several output options, which enables us to control what we output, and where. So, we can have music and mics going out through the main speakers, but just the music out through "monitor" speakers.

 

Most mixing desks have the facility of more than one output. Ours will allow us to use a sub mixer, so that we can have different volume settings going through our sub mixer. (All in addition to PFL).

[brianmole 0]

Does anyone use the Behringer feedback destroyer? I would be interested in a review/opinion as occasionally we get the muppet doing speeches trying to force a mic into a speaker!!

[ChrisPointon 0]

The feedback Destroyers do work provided you are patient enough to carefully read the instructions and spend a while setting up the system. Like Compressor Limiters, they can either work well, or do nothing depending on how well they are set up. But there is no easy to use, plug 'n' play system which can just be connected stright from the box.

[RobbieD 0]

You want to know about feedback eliminators? You asked for it. (You may want to go make yourself a cup to tea.)

 

As Chris says, these are no magic solution, and they take time to set up. Also I think a better term would be feedback reducer, as any of these units take a moment to catch feedback, and in extreme cases may not stop feedback at all.

 

Feedback reducers normally have two sets of filters: fixed & live.

 

The fixed filters do most of the work, and are set up in advance by pressing the right buttons, then slowly increasing the volume with the mics on, until they start to feedback. You will get the first whistle through the speakers, then hear the filter fade in, the whistle stop and an indication on the display that the first filter is set.

 

Then you increase the volume a bit more until the second filter kicks in, and so on, until you have set all the fixed filters (depends on unit, and application, but six is typical). This needs to be done before customers turn up, as the feedback whistles are unpleasant, and it looks unprofessional to anyone not understanding what you are doing!

 

But you can do the same with a 31 band graphic. Just slowly wind up the volume, and as you get feedback, find the slider that reduces it, and pull that one down, then wind the volume up more, and do the next one, etc. This process is called ringing out and this is what they do with the monitors before live concerts.

 

The other filters on a feedback reducer are the live ones. These kick in during the performance to catch feedback, but depending on the quality of the unit, may take up to a second to kick in. The live filters will then switch off after a set delay, ready to kick in when next needed. (But this may cause little bursts of feedback from time to time if not set up well.)

 

The live filters can also detect certain notes in music and think it is feedback, and this can affect the sound quality. Set up is a compromise between catching real feedback, and not reducing the sound quality too much. Unfortunately it is hard to get both.

 

I have both a Behringer Shark, which contains a feedback reducer and a DBX Driverack (260) which also contains one. The feedback reducer in the Driverack certainly works much better than the one in the Shark, although the Shark can be effective. The Shark works best when set up (ie ringing out) in advance. The DBX has good live filters, and the filter notches are much narrower, therefore affecting the sound quality less.

 

The DBX has several different modes including Speech and Music. The speech mode has a very fast response. So fast that it picks up on many parts of the music and drop filters in. But on a speech, this is ideal.

 

The same feedback reducer as used in the Driverack 260 is also in the Driverack PA and available in a easy(ish) to use, but expensive stand alone unit from DBX and I believe that the feedback reducer in the Shark is also available in several other units from Behringer.

[brianmole 0]

Top marks for the advice, many thanks. http://www.dj-forum.co.uk/html/emoticons/thanks.gif

 

Bloody tea has gone cold. http://www.dj-forum.co.uk/html/emoticons/biggrin.gif

[pac162 0]

thanks all ! great advice as usual http://www.dj-forum.co.uk/html/emoticons/biggrin.gif

 

if i were to get one..i'd probably have to go for the behringer as the dbx one appears to be quite a bit more expensive...but father christmas may come good http://www.dj-forum.co.uk/html/emoticons/rolleyes.gif

 

madgutts...you said that you use 2 feedback destroyers at your gigs....do you find that they require alot of setting up at each venue ? alot of my work will be at pubs so cant really have the speakers screeching away whilst im trying to calibrate the destroyer...out of interest..which unit/s do you use ??

 

http://www.dj-forum.co.uk/html/emoticons/thanks.gif

 

 

 

[blackmagic 0]

I dont know for sure but from what ive been told feedback destroyers only cum in after the feed back has been created, i know that doesnt make sense but lets just say the audience have heard the feedback by the time it cuts it out.

[fordmandj 0]

hi, just a thought on mic feedback, i have problem sometimes with feedback aswell and i have looked at a few feedback destroyers which only seem work when a range of frequencies reach very high levels and then cuts them out, so the audience hear it.

Does anyone know if you can get a feedback preventer?? something that, say gets the signal from the mic and delays it a few milliseconds, and then sends it to the mixer, then in theory, the mic should never hear itself and feedback, or is my theory wrong, If anyone knows of such a device, please reply to this post as i would be interested to hear about it, cheers, james

[blackmagic 0]

well i dont know but surly is that happened then the person speaking into it would have fun hearing themselves back a few seconds after theyd said sumthing, i would take some getting used too. If you were using it for singing then you have no hope bcause u would be out of time with ur music. Maybe i'm wrong i dont know. Can anybody give us some feedback on it (excuse the pun)

 

blackmagic

[d6184r03 0]

not sure about a preventer, but for what i have been told about destroyers is that they are rubish, if you do start to get feedback, i detects it, then kills that frequency, this sometimes makes you have good sound then all of a sudden no noise, or no base, but there is one in the bottom of the milton james http://www.dj-forum.co.uk/html/emoticons/whistling.gif

 

Dave

[RobbieD 0]

As an occasional user, and owner of two different feedback reducers within other equipment (see my post above), I’ll try and answer some of your questions:

 

QUOTE (blackmagic @ Dec 30 2004, 08:46 PM)

I dont know for sure but from what ive been told feedback destroyers only cum in after the feed back has been created, i know that doesnt make sense but lets just say the audience have heard the feedback by the time it cuts it out.

There is some truth in this, but it depends on the set up.

 

On my DBX Driverack (the best unit I have), in Speech mode, the feedback reducer will cut feedback in a fraction of a second and you just hear a quick peep sound. However you can’t use this mode on music, because it will quickly use up all the filters in a second or two as it miss-interprets notes within the music as feedback.

 

In the music modes it can take up to half a second at activate a filter and stop feedback, but doesn’t triger filters on music in the same way. But half a second of feedback can sound like a long time!!

 

As mentioned in my above post, it is a compromise between catching real feedback, and not reducing sound quality with unnecessary filters. You need to decide what is acceptable in your system.

 

But the better option is always use of quality microphones and better set up of your system to avoid feedback in the first place.

 

QUOTE (fordmandj @ Jan 1 2005, 07:25 PM)

hi, just a thought on mic feedback, i have problem sometimes with feedback aswell and i have looked at a few feedback destroyers which only seem work when a range of frequencies reach very high levels and then cuts them out, so the audience hear it. Does anyone know if you can get a feedback preventer?? something that, say gets the signal from the mic and delays it a few milliseconds, and then sends it to the mixer, then in theory, the mic should never hear itself and feedback, or is my theory wrong, If anyone knows of such a device, please reply to this post as i would be interested to hear about it, cheers, james

QUOTE (blackmagic @ Jan 1 2005, 07:38 PM)

well i dont know but surly is that happened then the person speaking into it would have fun hearing themselves back a few seconds after theyd said sumthing, i would take some getting used too.  If you were using it for singing then you have no hope bcause u would be out of time with ur music. Maybe i'm wrong i dont know

 

A delay would only slow down the feedback. The feedback would build up like a backwards ehco getting louder every delay cycle, rather than coming instantly. I guess this could give you time to turn down the mic before it got too loud. Also as Blackmagic says the delay would make it confusing to the user of the mic.

 

Another technique is to use a pitch shifter so that the voice comes out of the speakers a couple of percent higher or lower. But like a delay this just slows down the build up of feedback. However it wouldn’t be as confusing to the mic user (who would just think they sound different over a mic). But it would make a singer sound off key.

 

A better way is to use an equaliser to ring out the system in advance, as mention in my above post.

 

QUOTE (d6184r03 @ Jan 5 2005, 05:55 PM)

not sure about a preventer, but for what i have been told about destroyers is that they are rubish, if you do start to get feedback, i detects it, then kills that frequency, this sometimes makes you have good sound then all of a sudden no noise, or no base

Depending on the quality of the feedback reducer, the filters are very narrow. So rather than cutting all the bass, they only cut the around the frequency that is feedingback. On my DBX unit, this is a 60th of an octave. (Compare this to a 3rd of an octave on a 30 band graphic eq.)

 

But if you start to drop in several of these filters, rather than notice the whole sound, or a frequency band go missing, what you get is a reduction in sound quality.

 

At my NYE gig, they had a raffle earlier on, and I switched in the feedback reducer. I forgot to switch it back out until around 11.15pm, when I was wondering why the system didn’t sound very good. As soon as I switch it out, it sounded like I had just replaced some cheap crapy speakers with some high quality ones. (But no change in the level of bass or trebble.) Suddenly you could clearly hear what the words were on the song, and the separate instruments. The change in the quality was quite dramatic, causing a few people on the dance floor to look around, and one guy to give me the thumbs up.

[High Fidelity 0]

Having never used a feedback destroyer I was just wondering.

 

Can the feedback destroyer not just be placed between the mic and the mixer so it only works on the mic and not the music. http://www.dj-forum.co.uk/html/emoticons/533.gif

[Kingy 0]

I tried a feedback destroyer last year on a gig for a band, frankly didn't like it. I prefer to ring out the monitors instead.

 

Never have problems front of house, only monitors and then rarely.

 

I use a 15 band eq per cab on monitoring and a twin 31 band on Front of house.

[RobbieD 0]

QUOTE (High Fidelity @ Jan 6 2005, 01:53 PM)

Having never used a feedback destroyer I was just wondering. Can the feedback destroyer not just be placed between the mic and the mixer so it only works on the mic and not the music. http://www.dj-forum.co.uk/html/emoticons/533.gif

That would be the ideal place for it as it would only degrade the mic sound and not the music. (The mic would still pick up some music causing filters to trip if not set up properly.)

 

However most feedback reducers on the market have line level inputs and outputs. http://www.dj-forum.co.uk/html/emoticons/533.gif

 

I guess this is because they are aimed at live music where every instrument would be mic'ed up (and they would be used in a side chain, or feeding the monitor amps only).

 

The a Behringer Shark is switchable to be mic level in and out, but the feedback reducer in it is only average, and not particularly fast responding.

 

Like Kingy says, feedback is rarely a problem in a well set up system. I only use one because it is built in to my Driverack.

[superstardeejay 0]

The best solution is a good gain-before-feedback mic and careful positioning of speakers away from the performer. (taking into account reflections). Personal experience suggests Shure or Sennheiser. The feedback destroyers work (albeit sluggishly) and are best for avoiding speaker damage. Cure the problem at source, rather than masking the symptoms.