I have been thinking about a problem I have sometimes.

My wife (Sam) uses a Sennheiser condenser mic, Most of the time the sound is great, but whenever she puts the mic in a boom it has tendency to feedback.

No changes are made on the mixer, and it has been 'rung out' beforehand.
Any incite please?
Also, just for my own interest why is it that when the mic 'head' is covered with a hand it tends to feedback?


Thanks in advance,
John Denim.

Hi John

If feedback occurs more frquently when the mic is placed on a stand than when she holds it, it is likely because the direction that the mic is pointing in is different in each case. The more directional the mic that is being used, the more this will be noticable.

A user cupping their hand(s) around a mic head changes the pickup pattern. The hand acts a bit like a funnel and will help direct unwanted sound into the capsule.
For example a singer places part of the hand between mic head and her mouth sound coming from the monitor or FOH can be reflected into the mic.

HTH
Andy

Taking your second question first, on a directional mic (cardioid or hypercardioid) the back of the grill is just as important as the front. It's the slots and holes back there that create the directional pattern and, as soon as you cover them, you're converting the mic to an omnidirectional pattern.

As for more feedback with a stand mic, Pyramid is right to question the direction the mic is pointing. However, other things to look into would be:

-does you wife get a bit farther from the mic when it's on the stand, requiring a bit more gain?

-does the mic clip in any way obscure the rear of the grill (see the first paragraph above)?

-could the stand be picking up and transmitting vibrations directly to the mic?

Bob

What mic is it? Some of the mics are cardioid and some are hypercardioid. Therefore what angle the monitor is at is a big thing. If is cardioid then monitor straight on with the mic is the best best, if its hyper or super then the monitor 45 degrees onto the mic is best.

Could this in any way be related to the type of stage that you're on?

I experience this problem when doing sound for my missus. Its usually when the stage is hollow and boomy, and often hitting the low cut button on the channel helps. Although we did a gig a few weeks back where whatever we tried didn't help and she just ended up chucking the stand off stage

Dan

A concurrent post has been automatically merged from this point on.

Oh, and another point?

If it is the stage thing, where are you setting your PA (if you are)? I often find that setting the bins well away from hollow stages helps.

I think that the 2 points I'd look into first are Bobs final point



And Dangermous' point



Where is the feedback, is it low feedback or high feedback. It's unlike to be the above if its higher feedback, but if its lower then it would be the first thing I'd look at. Did I hear you mention a 31band graphic some time ago? It's probably time to get using this to clear it up. Make sure the HPF is on on the vocal channel or a start, this should get rid of a fair bit of stage rumble which of course will be much worse on some stages.

Let it feedback IN THE SOUNDCHECK. I know its difficult, there's often not alot of time, there's often people in during soundcheck, so pick your time wisely, but get it to feedback where it does and have a play with the graphic.

There's nothing wrong with boosting a frequency on the graphic to hear it start to ring so you can find the frequency. It should start to feedback quite early if its causing problems.

Mic model would help, is it an 865?


Rob

Indeed it is an ME 865.

The feedback 'type' is HF, not too high though, from memory I think around 6-7 khz.
The direction is not really changed, the only difference is the mic is in a stand rather than the hand.

This quote from Bobbsy is very interesting.

"could the stand be picking up and transmitting vibrations directly to the mic?"

I will have a play in a local hall I have access to, it's a shame it does not feedback the same way all of the time, then I feel it would be easier to sort.

John Denim.

High frequencies like that are unlikely to have much to do with the stand.

I'd find the frequency and remove it, or attenuate it at least.

Cheers Rob, I now possess a Dynacord powermate mk2 which has a built in notch filter.

Still, can't work out why the mic is prone to feedback whilst in the stand.
It's fine in the hand, maybe there is a small difference in postion, or the mic is teetering on feedback levels all of the time?

John Denim.

John is it a radio mic or wired?
we use a sennheiser e365 radio mic and when the sensitivity is set too high we get feedback problems although
it gives the mic a much fuller better sound.
if its not a radio mic please disregard my useless comment.

It is a radio mic, yes.

All of the equipment is packed away at the moment but I will certainly check the sensitivity.

Thanks.
John Denim.

without dragging the post off topic do people normally put their bins and tops on the floor if they are performing on a raised stage.
it seems to make sense so that you don't get the bass booming through a hollow stage and the speakers would be at the level of the audience but alot of bands I see seem to put everything on the stage.

A concurrent post has been automatically merged from this point on.



thing I've found john is that the higher sensitivity sounds much better...if you reduce it the mic sounded thinner to me..
I seemed to want a setting between the two that wasn't there :-(
I might try the better sounding option soon and use the dynacord feedback rejection to see how I get on as I have a cms1000 which is the same as your dynacord although it's not powered.

so far I've just taken the easy option so that we don't get too many problems on a gig.

I've not found any difference in sound when altering the sensitivity of the 365's (apart from the obvious difference in level). I guess there are lots more things to factor in aswell, pre amp included.

I find that a -40dB or -50dB would be nice!!!! With particularly loud voices these things still run out of headroom. Luckily they just sound a little compressed rather than alot of others which just distort and have even less headroom.



Rob

John - getting back to the original question - where are your monitors positioned? The mic in question is supercardioid, so will have a "lobe" directly behind the mic - which you would not get with a cardioid mic. Is there a monitor in front of the mic stand?

I'm sure you're right Rob as you seem to know alot more than I do.
I said this because about a year ago we were trying a sennheiser e365 against a shure beta 87 ( at least I think thats what it was)
the shure seemd to have alot more balls in it so we were changing the sensitivity on the senheiser to see if it made a difference.
it did seem that when we reduced the sensitivty of the sennheiser it sounded alot more boxy and not such a full sound.It sounded much better with the sensitivity up but then it could give some feedback problems.
this was not exactly a laboratory test as it was done in the middle of a rehearsal with 5 or 6 singers present so as I say I may be wrong and it could just be due to the level but that was my impression at the time.both mics were going through a dynacord powermate 1000.

It may be the case, I don't know really, I've not noticed this difference. But then again, I set them up in a room, and alter the sound to suit, so maybe I don't take enough notice. Then again, I have to admit, I can't remember the last time I used one of my 365's on anything but -30dB.

There are two monitors Bruce, namely Dynacord am12's.

they are postioned about 45 degrees each with the performer at 90.

John Denim.

Like Rob, I very much doubt that mid/high frequencies will be transmitted via the stand. I'd start looking a minor variations in position and aiming.

Is the stand mount set to be nearer horizontal while when handheld does she hold it more vertical? With a very directional mic this sort of change can make a difference. Or, at the risk of stating the obvious, does she handhold and "swallow the mic" when she's really belting and reserve the stand for quieter ballads?

Bob