Feedback, Sick of it

Posted: Sun Nov 23, 2008 4:51 am

Churches. Feedback. Rotten EQ. Grahh!
(Begin rant, skip to last paragraph to dodge)

The shape of the Church mixer's 10-band EQ gets worse every week, I tell you.
Notches 1 and 2 are down for low end rolloff. 4 and 5 are down to fight a lovely ringing, 7 is down, 8 is down to combat sibilance, 9 and 10 form a nice high end rolloff.
I could probably do away with the rolloffs but my problem lies around the 400-600Hz range.
The EQ bands are 315 and 630Hz and somewhere between them lies the ringing. So both have to go a few dB lower, taking with them the core of the sound.

I'm thinking that I should blast some (pregenerated) pink noise out of the speakers, and record the radio mic to create an impulse - to see if it shows the problems.
Will that work?

Posted: Sun Nov 23, 2008 6:03 am

Hand held mics in a room with a PA pointing everywhere?

Posted: Sun Nov 23, 2008 2:55 pm

That's what the annual pantomime might become.
But for now, we have to dangle mics from the ceiling.
Not a great advert for Church sound, eh...

Posted: Tue Nov 25, 2008 3:43 am

Monkey!
Location,location,location!!!!!!
Where are your speakers in relation to the mics? You have been on this site long enough to know that that is the BIG picture! I've used lots of hangin' mics with choirs, you HAVE to keep the monitors away from them, and keep the monitor mix choir-free.... Do you happen to know what make/model these "bats" (that's what one of the churches I used to work in called them, because they hang upside down) are? How many of them are you using?
Specifics, mon frer, we need info. Inquiring minds want to know...

Posted: Tue Nov 25, 2008 4:13 am

Let me guess: big stone church? That's a tough one.

If you are getting ringing, I wouldn't fight it with a parametric EQ. As moonbaby said, keep the bats out of the monitors. If you have trouble with vocal microphones have the vocalist get on top of them. If it's someone unexperienced doing announcements, there is not much you can do besides politely tell them later that the people in the back or in the lobby probably couldn't hear them because of where they were holding the microphone. If it is some one that is a good public speaker, you can motion to them to bring the microphone closer to their mouth. (You don't want to fluster those that aren't good at speaking in public.)

Why are you rolling off the highs? does it sound harsh if you don't? To fight sibilance I roll it down on the offending vocalist. Normally I can find one female vocalist that I can bring it up on to make the voices mix better.

Is the bass rolled off because it sounds muddy? Generally I roll the bass all the way down on the EQ of female vocals, and down a little on tenor, and boost it on the bass vocal. The parametic stays flat so the guitars and piano sound nice.

Rolling off the lows and highs is a live sound trick to compensate for a seriously underrated power amp. At the frequency extremes it takes more power to create an audible sound, so if you roll those off, that power can be used in the mid range which takes less energy to be heard.

IMHO: The EQ should be used to shape the sound not fight feedback.

Use a reference mix though the PA and adjust the EQ until it sounds right.

If can't get good sound thought the sanctuary at levels that don't ring, maybe you need some auxiliary speakers half way down 10-15 feet up on the wall.

Posted: Sun Nov 30, 2008 9:25 am

Ok, this is what it is. EQ will not be artistic. It has to be damage control.

If you don't have high-q speakers and mics with great off-axis rejection, this is all nuts. You cannot EQ out poor placement, poor speakers, poor mics and poor performance.

Crap. Let the feedback ring. If they get tired of it (assuming they hear it) they will give you a stage to present your case. You should consult three of the major consultants in your area. Then consult three of the top engineers from your local union. Have them all come in and document what is wrong, submit it to the church. If the church won't budge or cannot financially, then there is nothing to do but continue pushing out crappy sound and killing your services, which is not YOUR problem.

Posted: Sun Nov 30, 2008 3:00 pm

Sorry guys, been everywhere but here this week.

The band/singers are remarkably feedback free...no choir, and no bats (nice name). By "hanging mics" I was referring to a whole other rant.
The (current) problem comes during sermons, with the lapel mic. That changes everything, doesn't it [hides].

Admittedly the radio mic we use is probably terrible...unless it's not being used properly. It's been around longer than me so I made a silly assumption that someone was shown how to put it on properly.

It's a stone church. about 20m long, ~8m high, 8m wide with side passages. The chancel area is, 8m wide by 5m deep, with a few angled walls. Basically a mash of stone walls.

To check what rings most, would you recommend spitting pink noise out the speakers, recording it and making an impulse from it?
Then find a way to get rid of the worst frequencies. (A 31 band graphic?)

Part of the problem here is getting out of old habits and getting changes made - nonetheless...

Posted: Sun Nov 30, 2008 3:40 pm

Oh, also...
If I noted the name of the lapel mic correctly, it's a Shure 93, which is all it says on the back of the mic itself.

Yahoo tells me it's omnidirectional > Neutral

Shall I get a unidirectional mic on the Christmas list then?

Posted: Mon Dec 01, 2008 5:55 am

That 93 is definitely the wrong lav for your rig. I believe that's the "default" lav mic that ships with the Shure SLX systems, but it sucks. I made one of the churches I work with send it back. Definitely go with either the WL185 cardioid or the WL184 supercardioid. The "super" would be best IF your pastor/lecturer DOESN'T MOVE THEIR HEADS AROUND MUCH...GOOD LUCK ON THAT !
I have used the WL185 (cardioid) in fairly reverberant halls with good results. Even when standing in front of the house system, no feedback issues, decent voice reproduction. Try that out...

Posted: Mon Dec 01, 2008 11:53 am

Best to go on the cardoid then...

£120, first price I found. (Does $200 seem about right?)
This might be easier than I first thought...

Although I'll try and have a play about with the positioning in the meantime.

I know there will be an obvious answer but why would anyone want an omni for a lapel mic?

Posted: Mon Dec 01, 2008 2:54 pm

I would not use a lapel at all. I would do a Sony before the Shure anyway, and ideally a Sennheiser before all of them.

I would do a cheek mic. You need to get the mic closer to source.

Did you say it and I just missed it? Was the lapel RF? If so, the RF systems will compress and expand signal. So, if you compare a wireless version of the same mic you will almost always prefer the wireless for sound and sometimes for feedback control

Posted: Mon Dec 01, 2008 4:13 pm

ITT I said very little of relevance, just ranting...
I think it's wireless, however...
The receiver may be diversity based. It has 2 aerials, not that that says much.

Broadband feedback isn't so much a problem, it seems as though the main cause is ~500Hz getting back into the mic.
However that's caused by the other problem, that the mic is a bleeding (literally) omni.

Quality and richness of vocal isn't so much the goal here, and IIRC the minister reckons that cheek mics are too televangelical.

Wanted:
A non-hypercardoid unidirectional lapel mic, which is the cheapest option that fits the bill.
(Behringer excluded)

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