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Monitor feedback

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Monitor feedback

Postby Dave.jj » Sat Feb 18, 2012 9:29 am

Hi all...

I am not overly technical but will try to explain the problem I am having to see if anyone has any idea.

We are a guitar duo, we use a Gigrac 1000 with Peavey cabs and laney monitors, we use Vox tonelabs straight into the gigrac, so no amps.

For some reason two gigs back when we set up and started our sound check as soon as we turned up the monitors we had massive feedback so we had to use the headphone socket to run the monitors to get us through the gig, but of course we had no monitor control...just main volume.

We checked it out at a rehearsal and it was fine, but at our last gig it did the same again... we tried moving the monitors forwards, backwards... moved the mic's but still loads of feedback past no 3 on monitors....


If this makes any sense to anyone... any ideas?? could if me the monitor out plug??


Thanks in advance
Dave
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Re: Monitor feedback

Postby grab » Sun Feb 19, 2012 1:04 pm

You've mentioned everything except the one thing which actually produces feedback - the mics! What are they? Where are they pointing/positioned relative to the monitors and FOH speakers? What have you done with EQ on the mics?

In a small venue, you can easily get feedback from FOH into the mics, as well as from the monitors. Worth checking this.

Different rooms will behave differently, depending on sound-absorbing/reflecting surfaces/walls/floors, the shape of the place, the height of ceiling, and where you are in relation to walls/corners. You may be fine at practises, but a different room can give different problems.

Worth having EQ on monitors and FOH to control feedback in just this scenario. £100 for an uninspiring-but-adequate Behringer 31-band 2-channel EQ is not a bank-breaker.
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Re: Monitor feedback

Postby Bob Bickerton » Sun Feb 19, 2012 8:11 pm

I think we'll need a bit more info.

I'm not familiar with the gigrac but a cursory glance at the front controls indicates it should perform your task well, albeit with pretty restricted graphic EQ.

I'm perplexed that you had to use the headphone out to drive monitors. And you mention you had the Laney's on 3 which implies they're self powered or are the Laneys passive and you were referring to going past 3 on the gigrac monitor send?

So please advise:

Are the Laneys active ( on board amps) or passive (driven from the gigrac)?

What outputs on the gigrac are you using for the Laneys?

The gigrac can be configured to drive L and R mains plus monitors, which means that you can access the onboard graphic for monitors, but I'm not sure if this only applies to the monitor speaker out or if the graphic works on the monitor line out (if it has one).

You obviously should not be using the monitor speaker outs on the gigrac to feed the Laneys if they are active!

Model numbers and links to manuals would be useful too.

Bob
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Re: Monitor feedback

Postby Dave.jj » Mon Feb 20, 2012 7:44 pm

Thanks for your reply's guys...

Grab
We had the mic EQ flat, and we tried moving the mic's in various positions non of which made a difference.

Bob
we have 1 Laney cpx-110 Active and 1 cxm-110 Passive monitor.
http://www.laney.co.uk/show_downloads.php?prod=cxm-110&rid=14
http://www.laney.co.uk/show_downloads.php?prod=cxp-110&rid=14

Gigrac
http://www.soundcraft.com/products/product.aspx?pid=129

From your reply I think maybe we have found the problem... Yes we are running them from the monitor out, from your comment
"You obviously should not be using the monitor speaker outs on the gigrac to feed the Laneys if they are active!"

I assume that we should not be doing this? At this time we run to the active one and then link to the passive one.

Dave
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Re: Monitor feedback

Postby Bob Bickerton » Mon Feb 20, 2012 10:34 pm

It's very important that you are using the 'Mon Output' jack on the FRONT PANEL of the gig rack to feed the active wedge.

DO NOT use a rear speaker output.

The signal 'Mon Output' jack on the front panel still travels through the monitor Graphic EQ and is controlled by the monitor master volume.

If you have feedback you can try and notch it out on the graphic, but it's pretty broad band.

Bob
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Re: Monitor feedback

Postby Dave.jj » Tue Feb 21, 2012 6:58 am

Yes Bob that is the way we are running it.... from the front jack - Monitor output to the active monitor then linked to the passive. We have used it like this for a few gigs with no issues, but now we just keep getting this feedback. Our set up does not really change from venue to venue so why has it been ok and now its not?

We moved the monitors well away, moved them closer, tried moving the main cab's and the mic positions all with no effect.

We just can't see why this has started to happen, unless we should just run two passive monitors? or there is maybe a problem with the gigrac.
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Re: Monitor feedback

Postby Bob Bickerton » Tue Feb 21, 2012 9:25 am

Hmmm.

Are you saying that when the monitors are run at the same level as previously they feedback. Or are you saying that the volume of the monitors are now uncontollably loud?

If the former, then there's an EQ or room issue. Have you double checked the EQ settings on all your inputs, are you still putting the same monitor 'mix' through the wedges, is the monitor graphic EQ on the gigrac still working and have you optimized it?

If the later, have you checked all your level settings are the same as previously including the inputs on the Laneys. And do the Laneys have a mic versus line input switch and is this in its correct position?

Bob
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Re: Monitor feedback

Postby Bob Bickerton » Tue Feb 21, 2012 9:31 am

Just checked, you are going into the line input, not the mic input on the Laneys arent you?

Bob
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Re: Monitor feedback

Postby Mike Stranks » Tue Feb 21, 2012 9:49 am

Try setting-up as usual - everything connected incl main speakers and monitors, but don't switch on. Now make sure all your monitor send controls - the blue ones - are at minimum. This includes the monitor master send and the effects send to monitor - they're all coloured blue.

Now switch on and check the main speakers are working OK as you'd expect. Sing, don't just do the old 1-2.

If all is well, keep the main monitor send at zero and set the individual monitor sends (blue) to the number 5 mark. You should still not hear anything in the monitors.

Now gently increase the volume on the main blue monitor send. When does the feedback start? If almost immediately, try backing-off the individual monitor sends somewhat.

If you can't things under control now then maybe the input setting on the Laney powered monitor is too high. You need to bring that into the equation too.

You're tring to get best settings with three separtae "volume" controls here - the individual channels, the main monitor send and the input of the Laney powered monitor. As I've said you'll need to experiment with all three to get the best results.
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Re: Monitor feedback

Postby Mike Stranks » Tue Feb 21, 2012 9:57 am

... and following on from Bob's latest, make sure you're connecting the unpowered monitor to the 'External Speaker' output of the powered monitor and not the 'Line Link'.

If you've inadvertently done that then the unpowered monitor will be acting as a microphone into the other powered monitor! That can produce all sorts of interesting effects! I've seen it before...
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Re: Monitor feedback

Postby Dave.jj » Tue Feb 21, 2012 5:32 pm

Thanks guys for all your help, we have lots of things to have a look at.... as it happens I am getting together with my mate tomorrow (wed) night so we can set up and have a look.

I will post the results when I get home.

Thanks again for your help so far, look out for the report
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Re: Monitor feedback

Postby Dave.jj » Sat Feb 25, 2012 2:15 pm

Back again....

We set up at home so we could have a play around with settings, as suggested we had all monitor levels at zero.

It turned out that when we brought the mic monitor level up we started to get the feedback. So it looks like we will have to balance the mic monitor levels with the volume on the active monitor... it seems it will be a fine balance between the two.

We must have just been lucky not to have had this issue before?

Tonight will tell as we have a gig so we will see if we can now adjust things and get a nice monitor mix.

Dave
www.the2fbs.co.uk
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