Stage Mic Placement for avoiding Phase issues

[Adam Gold]

Seems there are a lot of opinions on this, based on the past few days of InterWeb research. Seems like every ten posters will give 11 different opinions. Passionately. Nonetheless, I'd be interested in the opinions of the experts on this.

Hypothetically, let's say I've decided to go with the suggestions from three other threads:

http://www.dvinfo.net/forum/all-thin...-zoom-h4n.html

and

http://www.dvinfo.net/forum/all-thin...sy-miking.html

and even

http://www.dvinfo.net/forum/all-thin...-opinions.html

and go with a nice shiny new DR-680 and three pairs of Rode NT3s or NT5s. In a nutshell, we've decided that mics on stands will be the best alternative; we will never use boundary mics again and the theatre isn't properly set up to physically allow for hanging mics. So mics on stands, even if they are not on stage themselves, will get us closest to the performers. They'd be on the floor in front of the stage, where a normal orchestra pit would be (we rarely use the actual pit for an actual orchestra, actually).

So the question involves spacing and aiming. I don't really expect a consensus on this but I'd love your thoughts. There seem to be fans of even spacing, stereo pairs or a mix of both.

Maybe I can express it typographically, with the lines below representing the mics and the numbers representing the percentage of stage frontage.

A. Evenly spaced across the stage, as in 20% | 20% | 20% | 20% | 20%.
B. Same as A, but outriggers angled in: 20% / 20% | 20% | 20% \ 20%.
C. XY Pair centered, outriggers angled in : / 50% /\ 50% \.
D. XY Pair centered, outriggers angled out: 25% \ 25% /\ 25% / 25%
E. Same ac C but ORTF centered.
F. Same as D but ORTF centered.
G. Two XY pairs: 25% /\ 50% /\ 25%.
H. Some other combination?

I've learned from you guys that phase and flanging issues are real and are to be avoided, so I guess that's my main concern here. (Thanks, Greg and Steve, for pounding this into me.) Seems to me all of the alternatives above would provide fairly even coverage, with four evenly spaced cardioid "pools" spread across the stage. These will all be going straight into the recorder and not to speakers, so feedback isn't an issue. My hunch is B is worst and D is best from a phasing perspective, but I'm usually wrong about this stuff.

Mics 5 and 6 will be on the orchestra, wherever they happen to be, in an XY pair. They're usually off to the side somewhere and rarely consist of more than six musicians.

Do these layouts make sense, and are there better ones? Again, hanging a Decca tree or anything else is not an option, so let's assume mics on stands are the constant.

Thanks for your feedback. Obviously we will experiment with this but I'd love your thoughts anyhow.

[Paul R Johnson]

I don't understand the problem. professional theatre people (like me) have sorted these kind of questions out for a long time, and we even have what was, (until they were discontinued recently) an industry standard.

The problem isn't phasing at all - it's comb filtering. A well known phenomena that gives the characteristic shimmering phasey kind of sound.

Without any doubt whatsoever, the most effective microphone is a PCC, it used to be a Crown PC166. The same designer has produced an excellent replacement - and a data sheet is here: http://www.bartlettmics.com/TM-125C_datasheet-color.pdf

Depending on the width, 2,3 or 5 of these seem to work best along the stage edge. A few people swear by short shotguns, but the problem is as people move across the stage, they go up down, up down and if you move them closer together to stop it, the dreaded comb filtering comes back.

The big problem with all these setups is that all they do is give you what's going on downstage - as people move away, that's that. Oddly, they don't suffer from stage floor noise that much, but if you get a stomp group in, a bit of thin foam decouples them enough without losing the boundary effect. best thing is that hardly anybody even notices them.

PCCs don't have too much pickup towards the audience, the rear lobes being quite gentle.

The Bartlett version has a nice video YouTube - TM 125 truck rollover

For fun we also made our own version which Bruce Bartlett thought was ok!
YouTube - blue room microphone

Look at almost any professional theatre and you'll see this kind of mic because they practically always do the job! If I saw anyone trying multiple conventional types, I'd really wonder. For video people, they're familiar with ordinary types, and rarely have these thing laying around - but in theatre low profile, excellent performance and the ability to blend seamlessly with each other is an everyday thing. For straight plays I've often just provided the video people with a feed of just these. We tend to emphasise the centre one and either run them mono, or with VERY gentle panning - certainly not left/right and centre - that sounds very strange.

[Adam Gold]

I never said there was a problem, only a question about which placement is best. Again, let's not debate yet another "which mic?" question, as this has been done to death. Really just asking about where you'd put them. We're dealing with kids here so even under the best of circumstances they're slightly louder than a thundering herd of Buffalo, even with plenty of foam, so boundaries are, as I said, out of the question. We've tried them and they are completely useless, not only in terms of stage noise but both reflection and their inability to "reach" upstage. Once the performers move more than six feet back they are inaudible. While boundary mics are probably serviceable for in-house sound reinforcement (because, especially in our theatre, there is a huge amount of high-quality sound going straight into the house from the performers themselves) these are clearly not meant for recording (as the mfr refers you to a different model for recording purposes) where all the video hears must come via mics.

Interestingly, these are referred to as Supers, while the ones meant for recording are regular Cards. And if you go to most mic mfrs pages, they call their shotguns either hypers or supers, neither of which are recommended for indoors. Interesting.

If you want to hear the audio we got with boundaries -- and really, I can't think of any reason you would -- I'll be happy to send you the same short snippet I sent to Greg that I mentioned in my last thread. The thin, horrible sound, excessive stomping and boominess and off-axis nastiness, as well as what I perceive to be phase issues -- are clearly present.

I was interested to see you recommend odd number of mics, generally, as does the mfr. Does no one ever use four? I guess I always think in pairs.

I know how tempting it is to answer a question that hasn't been asked, if the question is inappropriate, stupid or based on a false presumption. Heaven knows I've been guilty of this many times -- someone will ask what time it is and I go on about why an analog watch is better than a digital one. But I don't think that's the case here -- I've done a lot of research, listened to the advice of many people more expert than myself and, most importantly, tried out all these ideas in the real space during a real show and have tabulated my results. In your experience, boundaries are fine. In mine, they aren't.

And of course, I've betrayed my ignorance by confusing phase and flanging issues with comb filtering, because that's how others have referred to these issues. Appreciate the correction. But regardless of what it's called, how do I avoid it best? If you have an industry standard as to placement, can you share it with us? From the link you sent, it's simple: 17' apart. Got it.

Thanks for your input so far. I did look at the spec sheet and while these mics are probably okay for a boundary mic, the NT3 blows them away, specs-wise.

[Paul R Johnson]

Your making the classic mistake of reading the specs and guessing the reason. Everything that makes them excellent for PA is even better for recording because you can add as much gain as you like, and on stage, you have a huge noise producing hard floor - boundary mics pretty well take the floor out of the equation. The reflections from the hard surface in my book easily hide many of the tonal advantages in terms of flat frequency response. I've heard some excellent microphones give really poor results when used on stage. Some people try overhead pickup and the results on speech are pretty horrible, I've always found. Great for choirs, but for hearing speech with clarity, I can't beat boundaries.

The reason for not doing 4 is actually a very simple one. People stand on the centre line, so with 1,3 or 5 you will always have one close. 1 doesn't work too well for wide stages, so 2 is a good compromise - edge and centre being about the same. 3 across a 25-30ft width is perhaps pushing it, but 5 works pretty well. From my visits to different venues with stages up to 30 ft wide, 3 is probably the most common. We work with comb filtering all the time and it's a real pain - it's very frequent when actors sing close together, and the only solution is changing balance. Using mics across the stage width, video wise the simplest solution would be to record them multi-track and then alter the balance to minimise the phasey sound if it happens.

It's good to have different opinions, and I've no problems at all with people who don't like boundaries - but for me, they're a life saver. My work relies on clarity in the main, and I've found that gentle eq on a boundary - and I even use cheap one sometimes for more risky situations - really works for me.

I've always thought that it's good to get other people's input, then decide which version works for you.

[Greg Miller]

Originally Posted by Paul R Johnson

The problem isn't phasing at all - it's comb filtering. A well known phenomena that gives the characteristic shimmering phasey kind of sound.

Paul, with all due respect, I think you're splitting hairs.

You say the problem "isn't phasing" and then refer to comb filtering producing a "phasey kind of sound." Doesn't that rather confirm the fact that the terminology somewhat overlaps?

You and I know that comb filtering is caused when one audio source reaches two mics at two different times, resulting in a significant phase difference between the two mics. When the mics are combined, the result is comb filtering. (And it can change as the performers move around, causing the phase difference to vary with time; that result is sometimes called "flanging.")

Please don't beat up Adam about terminology; we are all talking about the same thing here.

And IMHO this problem will not be easy to solve, given that Adam can't use PZMs and can't hang mics.

--

Adam, to clarify this, one point at a time: do you plan to record an actual performance with audience present, or will you record at a rehearsal or special "performance for recording only"?

[Adam Gold]

Thanks for the clarifications -- very helpful indeed. But note I'm not the one who says these aren't for recording -- it's the mfr, who direct you to a different (more expensive) version. I'm not guessing, I'm just quoting. Or citing. Or something.

I would consider boundaries for concerts, where there is no movement. But for plays and musicals, I've learned not to go there. Boundaries may "take the floor out of the equation," but only if no one is moving on it.

By the way, Bruce Bartlett himself (maker of the boundary mics cited above) says this about the terminology:

When the direct and delayed sounds combine at the microphone diaphragm, this results in phase cancellations of various frequencies... This is called a comb-filter effect.

So it appears the terms are synonymous, or at least the latter is a subset of the former. So we're all absolutely correct.

As I noted earlier, each of these will go to a different track, so we will play with balance and panning and all that stuff to customize the sound, so maybe comb phasing and flange shifting will not be an issue.

Greg, we're doing this during the actual shows; otherwise (for the concerts at least) I could put the mics on stands right up in front of the performers on stage. I have no problem seeing the mics in the video; it's the powers that be who are paranoid about disturbing the "theatrical experience." To their credit, and to minimize their apparent craziness, I must say they teach the kids really well how to project to the back row, so it almost always sounds great live, particularly the concerts. Musicals, not so much, as the instruments often overwhelm the voices. Their emphasis is on live performance and video is really frosting, an afterthought.

The audience is indeed a rather significant issue. They are, ahem, enthusiastic -- many times louder than the performance. If I were to set my levels based on the loudest sounds in the house, you'd never hear the performers. It's happened. It was when I used the Auto Levels on the Zoom -- yes, I know -- and it stair-stepped down with each number as the audience cheered louder and louder. By the end the vocals were coming in at -80dB.

I mean, we could use hanging mics, but I just don't think we can get them close enough. By my rusty calculations of Pythagoras, a performer ten feet back from the front of the stage would be about 11 feet from the floor mic but about 16 or 17 feet from a hanging mic, based on where we could conceivably hang them.

Thanks again.

[Chad Johnson]

I've recorded a lot of plays with wither 3 or 4 mics. I put a Rode NT4 at the lip of the stage, front and center. Then I put an NT3 on either side, pointing in 45 degrees. It's picks up everything on the stage, and there haven't been comb filtering issues. The phase/comb stuff is usually do to big differences in mic distance. But with everything up at the stage, your good to go.

Another great mic for stage recording is the sure SM81: http://www.bhphotovideo.com/c/product/68479-REG/Shure_SM81_LC_SM81_LC_Cardioid_Condenser.html

[Adam Gold]

Chad, how far apart are your three mics? With the NT4 being an XY stereo mic, it seems a pair of NT3s or 5s would be the same and cheaper to boot, as well as being more versatile.

So that's a vote for "C".

Thanks for jumping into the pool on this. While I have you, any thoughts on the 3s vs. the 5s and in what combinations? All 3s? 5s? 3s on the orchestra and 5s on the stage? The Shure looks fine as well, but not dramatically different from the Rodes and a little more expensive, which only matters if you are going to buy six of them, as we plan to do.

(I'm really enjoying this discussion, because it's keeping me from working on yet another cringe-worthy pro-bono edit job with awful audio; while we had stage mics right up to the performers for this concert, the kid running the board either a) didn't open the mics until about 30 seconds into each song, b) jammed the sliders all the way up when he realized his mistake, resulting in enough feedback to bring the house down, and/or c) kept the levels so high that the distortion is unbearable, in which case I'm deleting that audio track and actually using on-camera audio and audio from my trusty backup Zoom, as it genuinely sounds better. I am literally lifting words and phrases from other parts of the songs to patch the holes. Such is my life.)

[Chad Johnson]

The NT3 has a 2/3" capsule, and the NT5 has a 1/2" capsule. So the NT3 will sound a bit fuller. So the NT3s on the side are better because most stuff happens in the center, and the further away you get the thinner a voice is. But also that (NT3) mic is bulky and heavy. It takes a 9v battery or Phantom, so that's a plus if you ever don't have phantom. The cool thing with the NT4 (which has 2 NT5 capsules) is that it's a perfect XY orientation, and runs on battery/phantom like the NT3. It's easy to set up and only takes one stand, which is good for keeping a ow profile.

I put the side mics close to the side of the stage aiming inward. It depends. I ask the director if there are any lines delivered far far left or right. If not, I bring them in toward the center a couple feet. I basically use my eyes to judge the width of the pickup patterns of the mics, ad try to have some overlap. That way I know wherever someone is they will be picked up. Of course people in the back of the stage are quieter. But all of them should be projecting if they are any good.

To answer your question, maybe 10 - 15 feet apart. That is center stereo mic, then 10-15' to each side I have the side mics. Phase isn't an issue depending on the distance the mics are from each other, it's an issue when one mic is a different distance from the source than another mic. But with dialogue in a play it isn't really an issue, as when a person is close to one mic they are much quieter in another mic. Where phase issues happen is when you have a mic say 5' away from the source, then you have another mic 25' away, and you mix both mics at the same volume. Then you hear phase/comb filtering. So when you keep the mics at a constant level the issues work themselves out for the most part. I just slap a bit of compression on each channel in the mix. EQ as well. Then a maximizer plugin over the whole mix. That helps to level out everything. The lame part is that you pretty much have to manually adjust the applause every time. It helps that all the mics are at the stage though.

In the case where a stupid stage director is having a hissy about seeing these silver mics, I use short black boom mic stand (tripod style for more stability) and I have taped a piece of black felt on the audience side of the mic. When the mic is just over the lip of the stage it pretty much disappears.

The DR-680 is a great recorder ! I have one, and I got a couple TRS-XLR cables so I can use channels 6/7. Those channels also pass phantom. So if you wanted to get 2 more mics, or a feed from the board that plays soundFX or music, you're covered. I love the DR-680!! I got mine modded for 300.00 by Busman Audio. He takes the already pretty quiet pres on channels 1-6 and makes them dead silent. Great for nature recordings, or if you record something too low and need to really crank it up in post.

[Greg Miller]

A few possibly relevant thoughts...

1.) If your "head artiste" can tolerate 4 or 5 mic stands, located in the pit area, at roughly the height of the stage deck (where everyone will see them), why can he/she not tolerate one hanging cluster of mics, at roughly the height of the proscenium, which would be out of everybody's sight lines? IMHO that would be a much better location. (Or does this auditorium have a balcony?)

2.) I have never tried recording with mics spaced out 1/3 width of the stage and angled in, so I cannot comment on actual experience doing so. However, in thinking about it and visualizing it, it makes me scratch my head.

Let's say you have one mic downstage right (not full right, but about half right) angled in about 45 degrees. If someone is standing fairly far downstage right, that mic will be the main pickup, and that person will appear on the right channel.

As that person moves halfway upstage, same distance from the CL, he will go out of the range of that mic, and will also be out of the range of the downstage left mic... he will fade away into the distance.

Then as that person continues upstage, he will eventually be on axis for the downstage left mic. At that point, he will start to appear on the left channel, even though he is located stage right.

I just don't think far-spaced crossed mics would give you a good kind of stereo image of the actual performance.

--

I'll leave off here until I get some feedback on these two points.

[Chad Johnson]

Actually the placement I described makes for a nice soundstage / stereo spread. I want a person on the right of the stage to come out more on the right speaker. I may not necessarily mix FAR R/L. Maybe 75%. And as I said I talk to the director to know the furthest left/right the cast will be, so as not to miss them. I have never shot a show that allowed, or had the ability to allow, hanging mics from above. Sure I'd do it, but never had the chance to. So my method, combined with reasonable compressors & maximization in post, will cover everything. I have never missed a line. If course if someone goes out to the audience you have to deal with that. But my simple setup is effective. One can always branch out from that. Or hang mics if you have the luxury.

I also have all the mics on shock mounts just in case.

[Adam Gold]

Chad, that info is great and much appreciated. Interesting point about the fuller sound being helpful at the extreme edges. Makes me just want to go with the 3s all around if that's true. And having six all the same will help when they go out into the audience or the side aprons, as they always seem to do with disconcerting regularity, screwing up my camera positions. But that's another thread. When you talk abouot a maximizer, that's the same as "Make everything the same", yes? Extreme compression?

Greg, your points are well taken. For #1, it's something we can try, but I just think it'll be much farther away. The seating is fairly steeply raked, so they'd have to be really high to line up with the top of the proscenium, and the closest place we could hang them would be over the third or fourth row from a catwalk above.

On #2, we'd have the center, and that's also why I thought having them pointing OUT would be better. This way, we have four "zones" and we can balance and pan in post in case we end up with the disorienting scenario you describe. So not thirds but fourths, with mics on the dividing lines, outriggers facing out. Or halves, with the XY on the center line, and outriggers all the way on either side, facing in. With spacing this far, anyone upstage right would be like 60 or 70 feet from the left wing mic, which I doubt would pick up much.

Either way gives you four little hearts on the stage which don't really overlap very much. At least as I visualize it.

I really feel like we're closing in on this....

[Chad Johnson]

Adam yy take on the center of the stage is that's where most of the action is. When you have the mics pointing out (otherwise known as ORTF) you get a dead zone right in the center. That placement is for when one records much further back in the audience. An XY will give you a big area that in many instances will cover the whole stage. The side mics are there to pick up when people are outside of the larger heart made by the center XY placement. And as I said with the NT4 you get phase accurate XY every time. If you are getting 6 mics, just get 4 singles and one stereo. I'm telling you, that stereo mic will come in very handy, and with 4 other mics you are totally covered. Just sayin... Try setting up 2 heavy mics in an XY on 2 stands some time. Very fiddly.

[Adam Gold]

I get what you're saying. We'd always do XY in the center and only the outriggers at the side could potentially be pointed out. With 30 or 40 feet between them, I'm not sure it qualifies as an ORTF. We may just have to play with this.

What you're describing is essentially C, above, but closer. I'm talking about D. If you picture that Cardioid "circle-heart" pattern centered over each "25" in line D, you'll get a sense of what I'm envisioning. The reason I like it is it avoids that weird long-distance crossing Greg describes.

[Chad Johnson]

Man 100' stage is huge.