Feedback elimination for RF mics

[audio]

Got a musical coming up soon, and the director wants 10 people with lavalier RF mics, maybe up to 6 on at once, which I have heard can cause many feedback problems.

I have used hand-held RF mics before, and was ok with them, just wondered how much harder lavaliers were going to be?

I am planning to put the mics in the actors hair - how do I hold them there?

I am assuming that I still set up the graphic equalizer just the same to eliminate feedback as I would if the mics were fixed - i.e. ring system and cut freqs where feedback occurs? Will this work even though the mics will be moving all over the stage?

Not planning any foldback, hall holds possibly 250 people and the band aren't being mic'd. Do you think foldback is a requirement?

Thanks guys

John

[James]

There are lots of ways of holding mic's at the hair line, ring of elastic, surgical tape, and florestry wire are three of the more popular ways.

 

You will have more of a problem with feedback if you consider how far away the mic's are compared to a handheld (Every time you double the distance between the mic's and the source you double the risk of feedback)

 

Try to get a parametric EQ rather than a graphic.

 

Set up your graphic on main outs as normal and set it so that the system sounds as you want it to.

 

Then insert a parametric on a group and use that to ring out your lavs. This way the harsher eq for your mics won't affect the clean feeds, (Music, FX playback etc....)

 

When I do halls of a similar size I don't normally give the stage any foldback by default but I do prepare to have some melody instruments only as a backup if the singers need it. likewise some simple foldback from RF mics on a hot spot for the MD if needed.

 

James

[Bobbsy]

I personally prefer "over the ear" to hairline as a mic position. It gets the mic a bit closer to the actors mouth (particularly if you manage to sneak the capsule slightly down the cheek!) and, to my ear at least, EQs out better.

 

I hold them in place by wrapping the mic lead in "ear loop wire" (flesh coloured florists wire) over and around the ear, and taping the capsule (well, the wire just behind the capsule) to the skin with surgical tape, Blenderm being especially good. Blenderm, BTW, takes makeup nicely, so with a flesh coloured capsule it can be pretty inconspicuous.

 

As for feedback control, frankly the best method is learning the script and mixing like mad. While I may OCCASIONALLY have six mics open at once, I'd pretty well never have all of them at "nominal" gain, preferring to "favour" the mic of the person talking/singing at any given time, with the rest pulled down half way or so.

 

Finally, as has been said, resist any requests for vocal monitors on stage. With any form of "hidden" mic, foldback is a BAD thing!

 

Bob

[audio]

Thanks lads.

 

Is a parametric eq hard to set up? Have been tempted to get one in the past, but thought a wider range of frequency control was availiable with a graphic - as you can adjust more freqs than with a parametric eq that adjusts 6 freqs?

[gareth]

Is a parametric eq hard to set up? Have been tempted to get one in the past, but thought a wider range of frequency control was availiable with a graphic - as you can adjust more freqs than with a parametric eq that adjusts 6 freqs?

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If you've notched down half a dozen frequencies on a parametric and you're still getting feedback, I reckon you've got bigger problems than a bit of EQ can fix and you need to look at what's going on elsewhere in the system! :)

[James]

If you have never used a parametric before then they aren't that scary.

 

Just at the point of ringing before you get feedback, take one channel of the PEQ in the right range as the guilty frequency. Give it about 3-6dB of GAIN, and slowly sweep up the band until you hit the exact frequency that rings. Then turn the gain to a cut and try to keep the Q as narrow as possible.

 

Give it some practice and it will surprise you how easy it is.

 

Repeat for the next couple of ringing frequencies.

 

As Gareth says if you have more than 6 problem frequencies then you have problems somewhere else in the chain.

 

If you get wide band feedback then back the gain off, you have reached the limits of the system.

 

 

James

[Jivemaster]

Cheap fence wire, welding rod or cut up wire coat hanger makes custom headbands or neck bands for rigging mic capsules over or under the ear. Tame sharp ends with heatshrink.

Vocal foldback will cause feedback they may just need a lead instrument feed

[Pete Alcock]

I'm in the middle of rehearsals for a modest production of Joseph (14 radio mics out), and have found a very neat (and extremely low cost) "coathanger" -type mic headset.

 

Part number MP33521 on page 535 of the 2004 CPC catalogue. They're only £5 each (curiously RS have them for about ten times that and they look identical). The point is you can bend them to suit the talent precisely, they have a plastic tip so you don't pierce the actor, and the mic element is heatshrinked onto the wire.

 

Sound quality is comparable with the mics supplied with Trantec and Samson radio mics.

 

Sorry, drifting off topic there. Feedback is much less of a problem than with the usual clip-ons because you get the capsule within an inch or two of the mouth and you don't have to get ingenious with bits of sticky tape and gum - you just bend it to fit, solder a connector on to suit the radio pack and put the actor's name on it.

 

ATB,

 

Pete.

[robloxley]

Sound quality is comparable with the mics supplied with Trantec and Samson radio mics.

Great!...

[audio]

Part number MP33521 on page 535 of the 2004 CPC catalogue.

 

CPC catalogue? whats that? can I get it online.

Will try and borrow one of events parametrics to have a mess around.

THanks to all

 

EDIT:-Just had a thought, would one of those feedback eliminators such as this or a shark be any use in stopping the feedback. Do they work? Because I could allow feedback to occur in the dress-rehearsal, which would then lock the filters for the production run??

[Andrew C]

Here, but no picture!

[Jivemaster]

Feedback eliminators workish but are not a total solution with highly mobile radio mics,

[Lamplighter]

I'm in the middle of rehearsals for a modest production of Joseph (14 radio mics out), and have found a very neat (and extremely low cost) "coathanger" -type mic headset.

 

Part number MP33521 on page 535 of the 2004 CPC catalogue. They're only £5 each (curiously RS have them for about ten times that and they look identical). The point is you can bend them to suit the talent precisely, they have a plastic tip so you don't pierce the actor, and the mic element is heatshrinked onto the wire.

 

 

Anyone found a source of flesh coloured or even beige heatshrink. I am trying to disguise these mics.

 

Brian

[Jivemaster]

Clear heatshrink over beige paint?

[Lamplighter]

Clear heatshrink over beige paint?

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Thanks for the suggestion, tests under way.

 

Brian