I'm having problems using a Mackie CFX12 and Mackie Thump 12 active speakers as a PA in a school. I set this up every week to run a 'showcase' in school usually using 2-3 mics. It's always a race against time but I try to soundcheck. I set the main mix fader to 30, have the channel faders down and the channels muted. The channels are assigned to sub 1 and 2 and they are set to unity. I get the performers to sing and adjust the gain till it peaks and back it off a bit. I then unmute it and raise the fader to unity. When I try to raise the main mixer fader to an acceptable level, I can never get it high enough without getting feedback. The space is very uneven by the way.

Am I setting it up wrongly or are there any suggestions as to how I can improve this?
Any advice would be much appreciated!

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He who can does........

Hi, Y

It sounds like you have no external EQ between the desk and the speakers. Cutting problem frequencies to counteract system (mic/speaker/room) resonances would help.

Do you have the option to move the speakers around to minimise resonances and to improve coverage?

What mics are you using and are they being used close up or being shared?

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

Thanks for the reply. I'm usually using a couple of AKG C1000's up as close as possible and sometimes a Sennheiser dynamic as well if there are three vocalists or an acoustic guitar. I've tried pointing the speakers differently but it doesn't make a huge difference. it's a very high space with two balconies and it comes in at both sides. I did try cutting the graphic on the desk at 1k and also the treble on the Mackie Thumps a bit, but it still didn't help much.

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He who can does........

With 2x electret mics and an acoustic guitar onstage it's understandable that you're having problems. I would expect the feedback to be fairly bassy and, as low frequencies are less directional than high, not improved just by pointing the speakers at a slightly different angle.

Things you can do for free:

Move the speakers as far away from the mics as possible and off stage (if there is one). Wooden stages in particular can have a whole family of bass issues.

Encourage the singers to project well so you're not amplifying a whisper.

Revise your expectations.


Things that cost money:

Get a few cheap, decent dynamic vocal mics. There is lots of info on these pages.

Invest in a decent Graphic Equalizer. The onboard one is useful for broad band adjustments but you need something more precise. There is lots of info... etc.

Buy a pickup you can easily and quickly fit to any guitar. There are many vitriolic and potentially violent arguments about this on these pages. Most folk will recommend the Fishman Rare Earth for normal acoustics (who am I to argue?). Classical guitars with plastic strings - you're on your own.

Buy a DI box - not Behringer. Advice, blah, blah...

p.s. The Fishman is fine, really.

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

The stage is a moveable one and the speakers are placed either side and slightly in front of the singers. Projection is a problem as many of the singers are kids who don't project when nervous in front of an audience! Once this happens I just can't turn it up enough to rescue the situation. if i move the speakers any further forward, the singers struggle to hear particularly if I'm putting a backing track through the PA as well.

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He who can does........

I agree with everything shufflebeat has said so far.

In my experience school halls are notoriously feedback-prone - far too may hard, flat surfaces...

I'd suggest you need to make sure that the speakers are well away from walls - behind and at the sides - and angle them to point down into the audience, using K&M Tilt Brackets - Tilt Brackets

As for the singers hearing themselves, these are surprisingly good and don't cost the earth.

You'd connect it to the Auxiliary Send 1 or 2 (set prefade) of the Mackie desk.

The reality is that you'll always be struggling if the performers won't project or go into whisper mode. Mics as close as possible to mouths - although that in itself is difficult when people are mic-shy.

Good luck

Edited by Mike Stranks (06/05/12 04:07 PM)

Thanks again to you both. The active monitors look a good bet. It's not a school hall which adds to the problems. It's in the dining/open area which has a huge ceiling and 2 open floors with balconies above it. The students sit in front and also fill the balconies to watch.On the right is a lecture theatre which projects out so wherever you point the speakers there's something the sound is bouncing back from.

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He who can does........

From what you say I suspect the room is not your main issue. Getting a good sound in any situation is made much easier by having a good, robust signal in the first place and perfomers who know what they're doing.

It may be that because your performers are a bit reluctant you're having to turn things right up to get any kind of sound. They're relying on hearing the main speakers. If they can hear what's coming out the speakers them so can the mics. Bad combination.

One possible (unconventional) solution that might be appropriate if the room acoustic is reasonable as you say:

Buy or put together some long XLR leads and mains extensions that allow you to put the speakers at the back of the audience (sensible cable routing please). This might sound odd but it's a bit like what people do in rehearsal rooms.

Performers hear a realistic balance and are more inclined to 'speak up' when they realise they can't be heard. Audience will soon cease to notice the speaker positioning. Speakers are far enough away from mics not to feed back so easily. Speakers are also facing the 'null' point of the mic where it is less likely to pick up the sound.

I've used this setup several times for a variety of reasons. If it suits your room and your people the fact that the audience and the stage are 'sharing' the same sound can make for a nice ambience.

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Ohm's Law states, "Your PA isn't as powerful as you think it is".