Boundary mics

[Ed_N]

Hi all, I've had a scan through the archives and I notice this topic has come up before, but I'd be grateful if I could get some advice on my particular problem.

 

I do the sound for an annual musical production that is put on in a church. Here is the first problem; the stage is totally open (no arch) and the room is very echoey meaning feedback is always an issue. It also means that mics cannot be positioned above the stage; only along the front.

 

For the lead vocals we have 7 Sennheiser Evolution radio mics which work very well. However I require some mics to pick up the chorus. In the past we've hired 2 Sennheiser rifles which I have positioned on floorstands at the front of the stage. These aren't giving particularly good results, as the cast move around you can hear different people being amplified as they walk past the mics! I'm also finding that during the soundcheck these mics feed back before they give the chorus any decent gain.

 

I'm a bit dubious about PZM style mics as our stage is temporary (made from boards on a steel frame) and is terribly noisy. So far I've been advised that 4 cardoids along the front might be good (such as C1000S's, ATM33a's or SM81's). Any further advice would be very much appreciated. The stage is about 10m across and of varying depths, however the chorus will only ever be about 3m away from the front.

 

Many thanks.

[paulears]

boundary mics win every time. Since buying some, I've given up on rifles (which I bought after seeing someone else use them, and didn't know any better). At a recent show I was asked to use a rifle in place of one. To keep the producer happy I put one in then let here hear for herself the difference. Out it came!

 

PZMs won't be much use to you in a church acoustic, but PCC's with their reasonably wide cardioid are worth a go. Noise wise - place them on small mic sized foam pads - the very open foam like scouring pads work well at decoupleing them from the floor. Ordinary cardioids like the ones you mention are very poor.

 

From my experience, the real snag will be that the floor mics will pick up those with the loudest voices, and these are usually the people who have been radio'd up anyway!

[James]

On the subject of this, has anyone tried the responce from the thomann PCC here

[Ed_N]

Thanks for that paulears. Forgive my ignorance, I don't really know how these PCC microphones work. My main concern is not just vibrations through the stage but also the noise of the troops marching around (especially during dances). My thought with mics on stands is that I could raise them up a bit away from the boards.

 

With the Crowns being on the floor am I likely to end up with an amplified elephant herd or is the pickup pattern such that this will be reduced?

[IanG]

Any microphone is only as good as the sound arriving at it. Whether you use shotguns, cardiods or boundary, they're going to have to be used selectively and as you need them.

 

For example, if you have cast on radios speaking and this is also picked up by your float mics, you'll have phase issues (much as you would with two radio miced actors facing each other). If you've got a stamping chorus, no amount of amplification will help if the stamps are louder than the singing.

 

You've also got the issue of gain before feedback - the more microphones you have open at any one time the less gain you can add before the whole lot falls down into howlround.

 

Despite PCCs being placed on the stage, their pickup pattern is cardiod and upwards from the mic, so if they are isolated with some foam or rubber they'll perform no worse than mics on stands. However - they can't just be left open all the time - only open them when you need them.

 

Aside from the technical issues - if you've got a chorus which can't be heard without amplification in a small (<250 people) venue, then either they're not singing loud enough, or the band are playing too loud. This is something you need to take up with the MD or the cast. Adding amplification in this situation will amplify the band as much as the cast, getting you nowhere.

 

If you're having feedback problems, it's probably also worth looking at whether your graphic eq (if you have one) can be used to take out a few dB of your most troublesome frequencies.

[Ed_N]

Thanks again for your advice Ian (I assume you're the same Ian G who has already spoken to me on another board!).

 

Yeah I realise there is no miracle solution, and indeed I'm sure the biggest problem with this year's production was that we had a smaller chorus. However I was just trying to find out what might be better than the 2 rifles we've been using in past years.

 

I should be able to connect up an EQ to help reduce feedback, definately something worth trying. On a similar note has anyone had experience of using automatic feedback eliminators? I notice Behringer do a rather cheap model. Any use or is it just easier to do it manually?

[paulears]

I've got a couple of those behringer units and must admit that for a rock and roll gig where monitor squeal is a snag, they work pretty well. I've found them no use whatsoever foh, especially with lavs. the notch they introduce kills the feedback, but is very evident in the overall sound. they also have a tendency to lock on to anything that is loud and pure in timbre - so a loud guitar solo through foh may well get notched if they hold a note too long.

 

A comment about the PCC's. I tend to use them on all the time, but usually via group, with an odd number of them so there is always a central one. this, fader wise is louder, with the others gently tapering off - not by much, but enough. The group once balanced can be brought up and down. I used to do what Ian does, but found in some of the smaller theatres that muting them totally also changed the ambience too much - leaving them up a little just keeps it a little 'live'.

 

Noises such as feet do get picked up, but not excessively so - in all fairness they pick up whatever noise is there - usually the person with the most out of tune voice who always seems to sing louder than everyone else - or this just me?

paul

[Just Some Bloke]

One other thing to point out is that all float mics, whatever the type and wherever they're placed, will pick up everyone in the area - chorus, yes, but principals too. So you'll be picking up some people on both the radios and the floats. This makes balancing the chorus to the principals really quite tricky if they're not loud enough to begin with!

 

In other words, if you're struggling to get the chorus through the mix, it's not necessarily your fault!

[Solstace]

On a similar note has anyone had experience of using automatic feedback eliminators? 

<{POST_SNAPBACK}>

 

Too add to this, I've used the (now somewhat elderly) Sabine FBX series units to good effect - I think the last one I used was the FBX-1020. This was at a wedding reception held in a rather large, reverberant school hall. The unit had two modes of operation (fixed filter and dynamic) 10 Filters were offered on each channel, and both channels were monitored independently.

 

Where 10 filters are available, I've usually found that assigning 5 to each mode is enough to cover most eventualities.

 

None of these "magic boxes" are foolproof - given the usual response time of 0.5s to as much as 1-2s, most good noise-boys (not yet sure I include myself in that statement) are quicker than the machines!

[IanG]

The unit had two modes of operation (fixed filter and dynamic) 10 Filters were offered on each channel, and both channels were monitored independently. 

 

Where 10 filters are available, I've usually found that assigning 5 to each mode is enough to cover most eventualities. 

<{POST_SNAPBACK}>

 

I disagree. With any "auto" eq units, I'd strongly advise not letting any filters run active during the show itself. Use them pre-show to ring out the 2 or 3 most troublesome frequencies, then leave them alone. Letting a unit run free will let it lock onto any sustaining note and notch it out, which sucks the life out of your sound.

[paulears]

Auto whilst live is just about ok for rock and roll - but totally unpredicatble with lavs on the go, as Ian said. The other thing is that they need to hear the feedback to kill it - by that time the audience have their hands on ears and if you duck the fader the filter won't lock on reliably. They need to hear real squeal to work. For me, in a theatre situation, would be unforgivable. Imagine explaining to the director "sorry about that awful noise, I had to wait for the filters to lock up" not good for repeat business.

 

again - as Ian said ok at tec - then don't touch.

[Ed_N]

Sorry to ressurect this rather ancient thread, we used some PCCs in the last production and they were certainly a lot more effective than the close-up rifles. However it was all pretty last minute and the onle foam-like substance I could find at the time were some car wash sponges which as you can imagine looked rather daft! Paul, when you say scouring pads, is this the sort of thing you mean?

 

http://www.grainger.com/images/products/5LG75.JPG

[dfinn]

Hi,

 

Bit off topic but with regards to rifle mics. I used 5 sennheiser rifles and a lot of the time the just died. They didn't sound too bad when the worked and to make them work you had to twist them so they unlocked a bit as they are in two parts.

 

Seems weird to me.

 

Daniel

[paulears]

  Paul, when you say scouring pads, is this the sort of thing you mean?

 

<{POST_SNAPBACK}>

 

Yup! They are exactly the right ones - the only thing to watch is that they have a tendency to move. make sure the pad is bigger than the mic area, and gaffer it, then double side tape the mic to the pad - if you gaffer the cable down, leave a little slack to prevent the cable removing the decoupling effect of the pads

[dbuckley]

...radio mics which work very well.  However I require some mics to pick up the chorus.

 

Although you almost have to do this, its never really satisfactory as the voices of the radio-miced principles have a tonally different character to the muck picked up by the stage mics, which as other have pointed out, is often dominated by the principles anyway as they have the stronger voices, which is often why they are the principles....

 

What I'm fond of doing is having a vocal booth backstage, with a few decent singers in it, to provide chorus reinforcement. Doesnt have to be posh, just a black dropped between a couple of bars, and a SM58 on a stand will get you going, though a stereo condensor and a few more bodies helps. Of course, you can turn a spare dressing room into a studio if you have the time / budget / enthusiasm / bodies.

 

The big advantage of the vocal booth is that the chorus voices "sound" like the principles voices, as they are relatively close miced. The MD can pick these people based on their vocal abilities alone, rather than their ability to remember a line, or twirly capability, or body shape or whatever. As long as the singers are accurately described in the program, then any accusations of the Milli Vanilli effect are satisfactorally dealt with.