Accordion live feedback

Subject: RE: Accordion live feedback
From: Bernard
Date: 04 Jul 11 - 04:46 PM

My learning has always been pretty much 'hands on' and trial-and-error, I've had no formal training. However, I work a sound engineer for my day job, so I've been obliged to learn!!

Whilst there are courses you can go on, there is no substitute for learning 'on the job' (so to speak!).

The term 'notching out rogue frequencies' (not red ones!) simply means using your ears to identify the note that the feedback is 'playing' - if you gently raise the volume until it just starts to squeak or grunt, that is the primary frequency to reduce - and a parametric or 'sweep' EQ is ideal for that - a Graphic EQ is likely to be less accurate unless it's at least 31 bands (1/3 octave).

Yes, I said 'reduce' rather than eliminate, because eliminating it completely can cause other problems, such as muddy sound. It's all a matter of compromise.

We call this 'squeaking out' the system, and you'll often find there are room resonances that affect everything, so should be dealt with first. You may even find the system itself has a resonant frequency (the old Bose 802, which I still use, honks at 1Khz, so you always notch that out by around -3dB before doing anything else!).

As Graham mentioned, a feedback destroyer is good for belt and braces - the Behringer Shark I mentioned earlier does just that.

A word of warning, though... over-use of any anti-feedback measures will inevitably result in lack of volume and/or clarity, so you are always looking for a workable compromise.

Compression can help, too, but with caution or the sound level will 'pump' - one loud note causes everything else to drop in volume briefly. You need to set a compressor-limiter so that it cuts in when the level is getting too high, thus limiting feedback simply because it's not letting the volume break through the 'ceiling' you have set... but you use this as the last line of defence, not the cure. Used properly, compression allows you to be generally louder and more evenly controlled. Used properly!!

Sorry there isn't a simpler answer - but that's why people like me are employed to deal with such problems! If it was easy, I'd be out of a job!

Subject: RE: Accordion live feedback
From: GUEST,Graham Bradshaw
Date: 04 Jul 11 - 05:29 AM

Hi guys,

Microvox pick-ups are renowned for feedback when pushed to loud levels. There are resonant frequencies which I think are around 250kHz and 2.5kHz, and the harmonics. As has already been said, notching them out is the answer. Parametrics are good for finding them, by sweeping the frequency until you find the offending one.

Once you know the frequencies, a graphic will work just as well.

In Peeping Tom, Ben uses a microvox on his melodeon. We set it up with a graphic on his monitor send, plus as belt and braces, we have a feedback destroyer on his channel. Never any feedback, and Peeping Tom can be a loud band!!

Oh, and please don't think I'm dissing microvox. I'm not. Alan Hughes, who makes them, is an old friend, and the sound of them is great. But, like ALL transducers and microphones (which is what they are), they have resonant frequencies which will cause feedback at high levels. Just needs to be dealt with!!

G

Subject: RE: Accordion live feedback
From: GUEST
Date: 03 Jul 11 - 10:13 PM

The poster, of course, is gargoyle....

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Contact or accoustic Mic?

Omni or directional?

Allow the acordian player to SIT on the pick-up ...bit NOT move their legs (large) - foam covers on the omnit mic - will probably work as well.

Subject: RE: Accordion live feedback
From: SteveMansfield
Date: 03 Jul 11 - 06:55 AM

How do you learn this stuff??? Is there a tuturioal video, as I would not know how to 'notch out a rouge frequency!'

Notching out a rouge frequency is very hard unless you suffer from synesthesia and see sounds as colours.

The rest (in my experience, obviously can't speak for the specifics of Bernard's learning) you learn slowly by hanging around with sound engineers, playing with as much kit as you can get your hands on, and paying attention whilst you're gigging going through other people's amplification rigs. The magazine Sound On Sound is a good resource as well. Like playing a musical instrument it's not something you can get familiar with through a magic bullet, more a gradual accretion of experience and interest ...

Subject: RE: Accordion live feedback
From: Herge
Date: 03 Jul 11 - 05:58 AM

Hi Bernard. How do you learn this stuff??? Is there a tuturioal video, as I would not know how to 'notch out a rouge frequency!'

Herge

Subject: RE: Accordion live feedback
From: Bernard
Date: 02 Jul 11 - 01:52 PM

Ahaa! The manual shows both 'zEQ' and 'ParaEQ' settings, which are exactly what you need on pages 21 and 22 - I'm assuming you have a hard copy version?

Anyway, the para(graphic) EQ should be fine to notch out the rogue frequency...

Also try a few of the zEQ presets to see if one is better than another - you may find you're using one of the 'vocal mic' presets which probably is totally wrong! There will be a mid-peak for vocals which could be causing your feedback.

Subject: RE: Accordion live feedback
From: Bernard
Date: 02 Jul 11 - 01:43 PM

It's not the pick-up system (I use the MicroVox myself), but the 'tone controls' (tech term equalisation). You need to identify the pitch of the feedback, and find a way of 'notching' it out - a Behringer 'Shark' is a useful tool, though you should be able to do it with the Tonematch mixer.

Most modern mixers use a 'sweep mid' EQ which allows you to select the feedback frequency and notch it out. The Bose Tonematch can do this, but it needs a bit of knowledge as you have to plough through menus to find what you need - and you need to both know what you're looking for and when you've found it how to use it...

Unfortunately my help can only be general, as I've never used the Bose Tonematch system... maybe someone else has more intimate knowledge of it and can be more specific.

Subject: Accordion live feedback
From: Herge
Date: 02 Jul 11 - 01:20 PM

Hi
Our accordion is giving us feedback problems regardless of our set up. We are 5 pience ceilidh band goimh through 2 BOSE l1 M2 systems vai 3 x BOSE tonematch mixers. Currently using accordion micrvox pick up system, but get feedback at higher levels. Have used mics as well, but the accordion is the only instrument in the line up gives us any problems. Any suggestion (not too technical!) or recommendations for a good quality pick-up system?

Regards
Herge