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seablade



Joined: 21/11/04
Posts: 4014
How much EQ for feedback is to much?
      #147363 - 25/06/05 04:48 AM
Just wondering what most people use for a rule of thumb?

I currently have a 12 filter eliminator on the system I am running, typically all 12 filters are active at a wide Q, but no more than half the size of a 1/3 octave EQ(Cant remember the exact size, I wanna say it is about a third to a quarter) and then on top of that I have found 2 or 3 frequencies that keep coming back and because said eliminator has already notched them I have had to notch them on a seperate 1/3 octave EQ as well, causing a severe cut on those frequencies, much more than I would like, but unfortunatly nessecary in this space(Outdoor Amphitheater and a center cluster located above center stage that would cost about 15 thousand US dollars to move) in order to get the volume I need out of the Omni mics we have(Wireless Lavs, Theater Performance so Omni is kinda a requirement), especially when considering 20 of them on stage on top of the area mics.

So I am looking to see really what other people use for a rule of thumb under standard operating conditions(Which I dont consider these to be, its a really poorly designed system for theater;)

Seablade


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Ultimate Fish
posting's fun


Joined: 06/12/02
Posts: 1910
Loc: York, UK
Re: How much EQ for feedback is to much? new [Re: seablade]
      #147366 - 25/06/05 05:36 AM
If you're not careful you end up turning down pretty much everything on the graphic and still getting feedback. I reckon if you start having to notch out too much you'd be better off looking at changing something else in the system if possible. The other consideration is the quality of the eq. In the past I've found horrid peavey graphics actually make feedback more likely.

--------------------
need to get rid of this stupid sig...


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James Lawford



Joined: 03/09/04
Posts: 61
Loc: Birmingham, England
Re: How much EQ for feedback is to much? new [Re: seablade]
      #147420 - 25/06/05 11:00 AM
When ringing out a system you find the first feedback frequency, cut a bit and repeat a few times. If you then push the system gain over the edge you will get all or most of the frequencies you had cut ringing at the same time. This is normal, you have just found your maximum gain before feedback for the system as a whole, with the mic setup you are using at the time. My advice to you would be to think more about mics and positioning and stop cutting too many frequencies on the graphics!

Also it can be useful to use graphics on a subgroup rather than the whole mix. Lets say your wireless lavs are feeding back but not the other instruments or handheld mics. When you cut the feedback for the lavs you are in turn detrimenting the sound of everything else. Consider routing the problem mics to a subgroup (or pair for stereo) and cutting the feedback that way. Far more useful than doing it on the whole system.

Also I would say, try some different lavs. What are you using at the moment? My church has just upgraded from a Shure Omni lav for our pastor to a cardiod and the rejection from feedback is great. Also something like the countryman E6.

Hope these helped you, any more questions post away!

James Lawford


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James Lawford



Joined: 03/09/04
Posts: 61
Loc: Birmingham, England
Re: How much EQ for feedback is to much? new [Re: James Lawford]
      #147421 - 25/06/05 11:01 AM
Oh yeah, also remember that for every mic open, you get 3db less gain before feedback, so use as little mics as possible! 20 omnis sounds like hell to me!!


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: James Lawford]
      #147473 - 25/06/05 02:50 PM
Heh while all the advice is good, most of which I already knew and cant apply to this situation;) Sorry about that. Setup cant change, because I am limited in resources. Cant move center cluster forward to the Front of stage, because of the price involved in doing so. Cant use anything other than an omni because of proximity effect, and in this instance there arent any handhelds or instruments, because it is live musical theater with canned music;)

I am curious though, when you say all frequencies ring back at once, you are talking essentially about a white noise effect assuming your EQ is set up correctly to give you an accurate reproduction of sound? I am assuming that white noise wont ever happen, but usually I am still having one or two frequencies per decibel of gain or so by the time I finish cutting things, so I am assuming this is not what you are referring to?

For the record the EQs in question are Klark Tekniks and Ashlys, the Klarks are on my center cluster, and the Ashly's are on other things, but not used for feedback because I dont get feedback out of the rest of my outputs. Thanks for the point about the quality of EQ, hadnt thought about that but it is a good point and makes sense in my head. Unfortunatly in this case I am not sure that is the problem, I havent heard anything bad about Klarks though.

But yea really right now with this thread all I am really looking for is to get a feel for when the EQ is to much, Most people agree with the when you get to many feedback frequencies at once?(Really need to buy a reference Mic sometime, unfortunatly because it is outdoor the reponse changes as the production goes on since the sun is setting right then;)

Seablade


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: seablade]
      #147475 - 25/06/05 02:52 PM
Heh and oh yea, I am aware of the 3db per mic rule, unfortunatly there isnt a choice but to have 16-20 omnis open at a time to get a full choral mix on stage that I am aware of sometimes;)

And I dont have the budget to buy 30 E6s(Though I would in fact LOVE using them having used them at other venues and love both the sound and the lack of problems with feedback they help with) at the moment, even after I can get them at about 250 US Dollars a peice, that is a good chunk of change, and the majority of my budget unfortunatly got spent for me on other things(And was only 2000 US dollars to start with;)

Seablade

EDIT: Currently using a combination of B3s and WL-93s since it was asked, nope I dont even have the money to replace all the WL-93s with B3s;)

Edited by seablade (25/06/05 02:53 PM)


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James Lawford



Joined: 03/09/04
Posts: 61
Loc: Birmingham, England
Re: How much EQ for feedback is to much? new [Re: seablade]
      #147582 - 25/06/05 10:33 PM
Hi,

Yep Klark Techniks are about the best graphics on the market though I havn't used an Ashly. (They are meant to be good though).

What I mean about the quality detriment of the sound is this.

The EQ you've used for the lavs affects the sound of the canned music if used on the main mix outputs. Hence: route all the lavs to a sub group (or pair) and use the EQ on the inserts of the subgroup. Then the music will be un - affected by the EQ.

Also, if you're only having feedback problems with a few of the lavs (probably not!) then just use the EQ on a subgroup with those lavs routed to it.

Make sense?

Our church has just brought (or just about to purchase) a Shure W185 lavalier for use with our ULX wireless gear. We were using the WL93 before and changed due to feedback problems. We get a heck of a lot more gain before feedback, and the tone of the voice is just as good for this usage. (Preaching.) The response tails off below about 250hz to account for the proximity effect. Of course the mic in question is quite a bit larger than the WL93 so that might be an issue for theatre, and anyway you can't purchase new mics so I'll shut up now!

Have you tried fixing mics nearer to the mouths of the people talking? I'm shure you know that already mind, just try and get the mics as close to the source as possible.

------------------------------------------------------------

In response to the question about all frequencies ringing:

What I meant was this: When you increase the system gain a frequency rings. You cut it on the EQ and the ringing stops. You push the gain up again til the same or another frequency rings then cut it. Do it a few more times til desired. If you then push the gain up quite a bit you will get all the frequencies which you had cut start ringing. You can also hear this if bypass the graphics after ringing out. It can be quite useful to hear just how much you have effected the sound.

Oh yeah, are there monitors on stage?

James.


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: James Lawford]
      #147643 - 26/06/05 09:28 AM
Good reminder on the EQ on the sub groups. Wont work in this particular situation though unfortunatly, but thank you none the less, it is something useful to keep in mind at any rate.

>Our church has just brought (or just about to purchase) a Shure W185 lavalier for use with our ULX wireless gear. We were using the WL93 before and changed due to feedback problems. We get a heck of a lot more gain before feedback, and the tone of the voice is just as good for this usage. (Preaching.) The response tails off below about 250hz to account for the proximity effect. Of course the mic in question is quite a bit larger than the WL93 so that might be an issue for theatre, and anyway you can't purchase new mics so I'll shut up now!

Yea I wish I could replace these mics for E6s, to be honest those are the best mics I have ever heard on a theater stage, and are now not much more expensive than the B3s used to be. Problem is I am so poor I am spending a fair amount of time repairing those Lav mics(Which is a pain in the arse by the way;) because I cant replace them even with cheap stuff;)

>Have you tried fixing mics nearer to the mouths of the people talking? I'm shure you know that already mind, just try and get the mics as close to the source as possible.

Heh Yep, unfortunatly with WL93s especially they kinda stand out;) Course get them to close and the element peaks before the signal even gets to the pack, had this happen with MKE2s? I used on stage, sennheiser element looks very similar to the B3s?


>What I meant was this: When you increase the system gain a frequency rings. You cut it on the EQ and the ringing stops. You push the gain up again til the same or another frequency rings then cut it. Do it a few more times til desired. If you then push the gain up quite a bit you will get all the frequencies which you had cut start ringing. You can also hear this if bypass the graphics after ringing out. It can be quite useful to hear just how much you have effected the sound.

See how much of a cut are you referring to though? For example I have come across two particularly bad frequencies in the space, that I took out with an eliminator, but then that came back on top of that cut that I then added another 6db cut to to get rid of, meaning that one frequency was cut a severe amount. I am not to good at cutting with a 1/3 yet, still working on that, so I am trying to get a feel of when it is to much.

>Oh yeah, are there monitors on stage?

Yep however I am paranoid enough about feedback in this space and the stage doesnt get to loud for the actors to hear themselves so their mics are NOT put through it;) 2 Side Fills Upstage and Downstage and 2 small jf60 Front of stage. Not a bad sound at least and can be made fairly even as needed, though the two DS side fills have a wide enough horn to cover half the audience and I am looking at moving the music out of the center cluster to those speakers instead. Havent fully decided, gonna give it a test run in a Tech coming up.... tommorrow. Oh yea, goodbye sleep.

Seablade


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griffter



Joined: 26/03/05
Posts: 43
Loc: London
Re: How much EQ for feedback is to much? new [Re: seablade]
      #147899 - 27/06/05 08:13 AM
I would almost certainly use a decent parametric EQ on the subgroup insert for the Wireless Lavs. With a parametric EQ you can finely tune the specific frequencies that are ringing and notch just a fine band out. You will keep the audio spectrum far more intact than by using a graphic across the main outputs


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: griffter]
      #148005 - 27/06/05 01:13 PM
Heh the catch is, the lavs are not just on one group, they are on as a minimum 4 groups, usually more than that, not including the other wired mics that are around. And at the moment I dont have a good parametric, and dont even have enough good graphics to do that.

Seablade


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Ultimate Fish
posting's fun


Joined: 06/12/02
Posts: 1910
Loc: York, UK
Re: How much EQ for feedback is to much? new [Re: seablade]
      #148015 - 27/06/05 01:37 PM
The Behringer parametrics are actually pretty good, maybe worth getting some of these. Also the cheapo behringer analogue graphics came out very well in a pro audio web shootout. In fact I think those guys were rather shocked at how good the behringer was.

--------------------
need to get rid of this stupid sig...


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: Ultimate Fish]
      #148062 - 27/06/05 03:25 PM
Heh Budget right now that i have to last me the rest of the summer is under 200 US dollars. That includes all repairs that I will have to do since this is an outdoor amphitheater in high heat and humidity environment. Plus having worked here last summer I know it will happen from that;)

Buying new equipment really isnt an option. That is why all I was looking for was a general feel for when the EQ is to much(Other than the obvious it sounds like crud;)

Seablade


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: seablade]
      #148093 - 27/06/05 04:54 PM
Heh well actually that budget just dropped down even more. Was trying to track down some connectors because the genius that installed the system in this space decided it would be a great idea to rip out all the speakon on the speakers and wire the place for hubbel twist-lock connectors and put those on the speakers...

Problem being now I am out of speaker cable and those connectors are 16 bucks a peice. I can refit the speaker with the original speakon and get a connector for the end for less than the price it takes to get one of those connectors...

Unfortunatly there goes even more of that budget;)

Seablade

Really wants to kill whoever idiot sound person installed these.


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griffter



Joined: 26/03/05
Posts: 43
Loc: London
Re: How much EQ for feedback is to much? new [Re: seablade]
      #148300 - 28/06/05 08:45 AM
As Ultimate Fish said, If you are having to pull many bands of eq on the system just in order to get a useable gain, You are fighting a losing battle. The basic system design is wrong, I appreciate you cant go moving clusters etc but there has been many good suggestions here, all of which you have said are no good in your situation, You have to be willing to change something in your setup as you wont beat the basic laws of physics!


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: griffter]
      #148942 - 29/06/05 04:55 PM
>As Ultimate Fish said, If you are having to pull many bands of eq on the system just in order to get a useable gain, You are fighting a losing battle. The basic system design is wrong, I appreciate you cant go moving clusters etc but there has been many good suggestions here, all of which you have said are no good in your situation, You have to be willing to change something in your setup as you wont beat the basic laws of physics!

But here is the thing, willing and able are two different things. I am not ABLE to move the center cluster, it is not a matter of willing, believe I would love to myself, it would make things MUCH easier. I am also not able to buy new equipment.

I know my sound system design is all wrong, I knew that one last year, what I am trying to do is do the best I can with what I have availiable.

The point of my original post was not to illicite suggestions for improvement, though I dont mind them so much really, it was more to get a feel for when I need to stop and just call it art(Notching Frequencies that is). I am unfortunatly not able to do much more than I have already to improve the system I am referring to.

Seablade


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: seablade]
      #148943 - 29/06/05 04:58 PM
>But here is the thing, willing and able are two different things. I am not ABLE to move the center cluster, it is not a matter of willing, believe I would love to myself, it would make things MUCH easier. I am also not able to buy new equipment.


Just to give you a reference, the center cluster is made up of 8 400 Pounds Cabinets(Cant remember my metric conversions right now sorry;). ALl of this is flown and currently rigged in such a way that in order to get any of them down would require renting a boom arm truck to get at the rigging(Yep we checked on this, had a few rigging friends of the PM come out and take a look at it) Overall to just safely get the cluster down is 15 thousand US dollars. It isnt a matter of wanting to move it, we both want to move it, we just wont have that kind of money for a VERY long time.

Seablade

PS For the record we both came into this venue to replace people that were already out there, I claim no responsibility for this system design;)


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James PerrettModerator



Joined: 10/09/01
Posts: 10826
Loc: The wilds of Hampshire
Re: How much EQ for feedback is to much? new [Re: seablade]
      #149275 - 30/06/05 11:37 AM
I'm intrigued by the need for 16 - 20 mics for the choral stuff. This sounds too many - where are they all? You're not trying to mic up individual performers are you? There's probably a better approach that uses fewer mics (floats?).

Cheers.

James.

--------------------
JRP Music - Audio Mastering and Restoration.
http://www.jrpmusic.net


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seablade



Joined: 21/11/04
Posts: 4014
Re: How much EQ for feedback is to much? new [Re: James Perrett]
      #149442 - 30/06/05 04:57 PM
>I'm intrigued by the need for 16 - 20 mics for the choral stuff. This sounds too many - where are they all? You're not trying to mic up individual performers are you? There's probably a better approach that uses fewer mics (floats?).

Heh unfortunatly I am not so sure there is. This is where theater differs from music tours I think. I already am swapping off mics(Somewhere between 20 and 30 swaps in this show alone I believe), but the shows are large enough, and the venue large enough that pretty much everyone is needing to be miced if they have a spoken line or solo line in a song. As it stands right now that doesnt happen because I dont have enough mics though, and I have some people walking up next to others and singing into the other person's mic(Usually the mics are placed on the ear to keep them out of sight) during certain songs, eh, it doesnt sound great but I suppose it is better than nothing.

Seablade


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