View Full Version : Mics for stage
Bob Krieger May 9th, 2015, 02:56 PM Before y'all bust me for posting about stage audio, I thought I'd ask the knowledgeable bunch here to see if you could impart a few words of wisdom.
I was asked to provide a permanent audio solution for my school. The system works fine, I just need to add up to 8 additional wireless lavs, handhelds, and/or headset mics. I'm not worried about the different mics, per se, it's the mic/receiver combos that I have questions about. I have a budget of about $2500.00. We have a 16 input mixer already in the system and need up to 8 additional wireless systems. The space is about 75' wide by 100' deep, so not overly large. The receiver(s) will (should) be rack mounted in the space, so walls won't be an issue.
Any thoughts on make/model? Recommendations on what to look at and what to stay away from? FYI, the mics will be for stage productions (child actors mainly) and some clergy/choir when the space is a church.
Thanks for any input!
Richard Crowley May 9th, 2015, 03:23 PM $2500 for 8 wireless mic kits comes down to $312.50 per kit.
A $300 wireless mic kit is well below the threshold of what most people here would consider to be a minimally-acceptable kit.
For several years , the Sennheiser G3 has been considered by most people to be the lowest-price kit that is worth the investment. Below that tend to be cheap, fiddly, plastic, unreliable, disposable toys. Furthermore, schools are particularly hard on equipment, and even G3 may not be up to the task of surviving in a school environment except for occasional use under close supervision by competent adults.
However, there are a new generation of digital wireless kits that use the 2.4GHz ISM band. The advantages are that they can be higher quality than most of the older-generation analog equipment. But the disadvantage of wireless in the 2.4GHz band is that the band is shared with WiFi, Bluetooth, and even microwave ovens.
Some big names in microphones are selling the 2.4GHz kits like the Audio-Technica System 10, and newcomers like Rode are now also selling 2.4GHz kits. But it may still be too soon to see whether these 2.4GHz products will be found reliable out in the Real World where they are competing with WiFi and Bluetooth, etc.
Paul R Johnson May 9th, 2015, 03:31 PM I've had a few racks of original series then G2 and G3 in schools and they survive very well - the packs are tough and resistant to damage, and dropping them seem fairly forgiving. The cheaper than G3 range - the XS are pretty good with the hand held, but the lav packs area bit more 'bendy', but still seem pretty good, and pricing is better than the G3. Schools and colleges often use disposable mics rather than the usual expensive higher quality ones, because these are the bits that get wrecked, but low cost chinese ones work well enough.
Brian Berg May 9th, 2015, 04:13 PM Shure are very common in many concert systems. The ULX is widely accepted, but you pay for that quality.
A good combo system with a lav and a handheld will run about $2k.
Shure ULXD Single-Channel UHF Handheld and ULXD124/150/C-G50 B&H
We're running a show with 3 R&B acts tonight with UR2's with Beta 58's.
A good cheaper option is the standard version of the ULX. I just put one of these in our church. Shure ULX Standard Series - Wireless Combo ULXS124/85-M1 B&H
Be aware that with combo systems, you can't run the lav and the handheld at the same time.
I just put two of these in our church for a forward thinking 2.4g system. Shure GLXD24/SM58 Handheld Wireless System GLXD24/SM58-Z2 B&H
www.sublime-lighting.com
Paul R Johnson May 10th, 2015, 01:41 AM What makes a huge difference in multichannel installs is the extra equipment, and this is missing from your budget. Distribution amps, remote aerials etc. Very often a distribution amp to feed multiple receivers from a pair of better aerials might cost as much as the individual package with mic, pack and receiver! Multiple receivers with front or rear aerials are a weak link, on the back they are often screened by the racks, and sticking out the front they get knocked, can't be set at the optimum angles and to see the receiver, can't be mounted high up.
Bob Krieger May 13th, 2015, 08:19 AM Thanks, y'all for the helpful replies. At first it seems like "I can't get there from here" with my budget. Also I didn't think about antenna distribution and such. I'm going to look at your suggestions, work up a tentative (larger) budget and see what the powers that be say.
Jon Fairhurst May 13th, 2015, 11:48 AM Bob,
I'm curious if you already have a general stage mic solution in place, or are you are using on-talent mics exclusively? Of course, good wireless lavs are ideal - especially for lead actors and soloists. To reinforce ensembles and choirs, a general solution might be a match for your budget.
I've been asked to put together a small system from scratch for a 20 foot stage. The budget won't cover wireless (yet), so I plan to start with floor mics. I'm looking at using these: Bartlett Stage Floor Mics - Bartlett Audio (http://www.bartlettaudio.com/collections/stage-floor-mics) They've been recommended on other threads on DV Info over hanging mics. (Unfortunately, we have a non-technical person who is pushing for hanging mics. Oh well...)
Anyway, let us know what you have in this regard. Maybe a general solution (or improved general solution) and fewer additional wireless channels will help you move things forward within budget.
Paul R Johnson May 13th, 2015, 03:16 PM What sort of productions Jon? PCCs like the Bartletts are probably the best distant mic setup - but keep in mind that while it will lift the chorus, or a choir, the amount of gain they offer is very small - if you need people to be heard over the top of a band, a small orchestra or other noise making group, they won't be much good. Very often you raise 3 or 5 faders to the point when it almost feeds back and then when you prod the mute buttons, the volume change is extremely small. Great for a recording feed to a camera or audio recorder, but for volume through a PA, you may be disappointed.
Don Palomaki May 14th, 2015, 05:22 AM The Shure web site has a FAQ and white paper section somewhere. It may provide some basic information on this type application.
Also, are you looking for hand held, instrument, lav, head-worn, ensembles, or a mix?
Many pro audio sources offer substantial discounts to schools.
John Willett May 14th, 2015, 06:36 AM Minimum would really be a Sennheiser G3 system - and you would need the antenna distribution that is part of the system.
You will need careful frequency planning with an 8-channel system - if you already have radiomics and you are adding another 8 - then you will *really* need careful planning.
You should only use 1 pair of antennas and then split these to the receivers - if you are not an RF expert, then I would get proper advise about how to set this all up, especially if you are adding to an existing system.
Sennheiser in Germany, the UK and the USA all have these experts who can properly advise you on how the best way to go about this is.
If your existing system is just a few cheapo systems - then I would strongly advise getting d of these and buy again as part of the new system as this will be much safer.
Jon Fairhurst May 14th, 2015, 12:34 PM What sort of productions Jon? PCCs like the Bartletts are probably the best distant mic setup - but keep in mind that while it will lift the chorus, or a choir, the amount of gain they offer is very small - if you need people to be heard over the top of a band, a small orchestra or other noise making group, they won't be much good. Very often you raise 3 or 5 faders to the point when it almost feeds back and then when you prod the mute buttons, the volume change is extremely small. Great for a recording feed to a camera or audio recorder, but for volume through a PA, you may be disappointed.
Hi Paul,
In my application, we need some reinforcement so people further from the stage can hear the voices. There's usually no recorded music during the dialog. The stage is small (20' x 15') and the room is maybe 80' x 40' with maybe a 15' ceiling. It's very live. The productions usually have a small number of speakers but might have a number of very young kids singing or chanting. The audience would typically fill about 1/3 of the room. The kids can be quite young with amateur volunteers directing things. Clipping on mics and transmitters and managing a complex mix isn't really in the cards. We'd be more likely to have a small number of wired handheld mics than wireless lavs when we need a commanding voice. The floor mics (or hanging mics, if they would be better) would be to provide subtle fill for those without a mic.
I don't want to hijack the thread. (The multichannel wireless topic is fascinating.) I guess it comes down to two questions:
1) When can a general mic setup be helpful (or unhelpful), and
2) Are floor mics or hanging mics preferred?
BTW, I plan on including a feedback killer / EQ to allow moderate gain without pain. ;)
Hopefully, the answers will benefit Bob and his application/budget as well as my more modest situation.
Don Palomaki May 15th, 2015, 06:00 AM The kids may be too young to manage wireless mics in the form of body packs, etc. and it adds a level of complexity to the production that may be difficult to master if it is largely based on volunteer (parents?) and staff that does not have the necessary technical bent.
1 - Add some wall & ceiling acoustic treatment to manage the room reverb.
2 - Use directional floor mics for the "stars," they can be wired. Teach them to get close to the mic.
3 - Use some directional ceiling mics for the ensembles/chorus
4 - Manage the gain carefully durning set-up and performances - it isn't a rock concert so you do not need those ear drum shattering, feedback producing levels.
5 - Be careful about speaker placement
Jon Fairhurst May 15th, 2015, 11:37 AM Great tips, Don!
I hadn't considered the combination of floor and ceiling mics. I had been thinking OR rather than AND.
Regarding treatment, the space has two separate boxes - the stage and the room. There is a partial wall at the sides and ceiling of the raised stage that divides them. I think we can reasonably treat the stage area to some degree. The audience area has glass on a side wall and is really too big for us to treat. I plan on mounting two 2-way 12" speakers from the ceiling just in front of the stage ceiling wall. That should cover the audience well without getting in the way and without radiating back to the stage. The delay from back wall to the stage should be long enough (120ms or so) to avoid squeal. The speakers will be aimed such that the front rows hear the performers directly with the reinforcement starting a few rows back.
I like "selling" the concept of floor (stars) and ceiling (ensemble) mics. I plan to start with the floor mics and add the ceiling mics if necessary.
And yes, managing gain conservatively should be realistic. It's not terribly hard to hear people as it is. They're not competing with music, aside from the occasional unplugged acoustic guitar.
Back to the original poster's question, I wonder if stage/ceiling mics would help that application or if it would be money spent for no gain (pun intended.)
Paul R Johnson May 15th, 2015, 01:36 PM hanging mics are quite common, but look pretty horrible at the kinds of heights where they are effective. On stage they also pick up a lot of reflections from the stage floor, which combine with the direct sound to sound typically hollow and distant. Boundaries on the stage floor use the stage surface as the plane, so are more effective and sound nicer at the same kinds of distance.
If you just need a little extra, then boundaries - PCC, not PZM to avoid too much being picked up in the audiences direction are the best you can do, if you don't want the grief that comes with radios - which are the opposite of set and forget.
Jon Fairhurst May 15th, 2015, 02:29 PM Paul,
How would you compare the Crown PCC to the Bartletts? As I understand it, Bruce Bartlett designed them both.
Crown Audio PCC-160 Phase Coherent Cardioid Microphone (http://www.bhphotovideo.com/bnh/controller/home?O=&sku=179590&gclid=CMm81ebLxMUCFUZafgodxRgA5Q&is=REG&Q=&A=details)
Bartlett Stage Floor Mics - Bartlett Audio (http://www.bartlettaudio.com/collections/stage-floor-mics)
Paul R Johnson May 15th, 2015, 03:17 PM Yep - he did, and he's a nice guy. I even did a parody of one of his videos and he thought it was funny.
The PCC-160 was a standard for theatres (perhaps even still is). Some people say the new ones - the stage and the recording version - are a bit brighter, but personally to my ears, they sound very similar, although the Bartlett design is a little more heavy weight - and a bit smaller. The Stage version is a direct replacement for the old PCC-160. It sounds a little different - but close.
Worth noting that they do a version with a cable gland rather than the mini socket. Standing on these, or in the case of dancers, jumping on them can cause problems when they snap!
Jon Fairhurst May 15th, 2015, 04:10 PM Yeah, I was wondering about the preferred connector. From the website, it sounds like the captive cable version is more robust. I like robustness! I would guess that the connector version would be better for road shows (for breaking down equipment from cables for transport) and the captive version would be preferred for fixed locations.
Warren Kawamoto May 16th, 2015, 09:17 AM I came across this thread, so I put up a sample of the Bartlett TM-125 which I used as a backup stage mic for a shoot last week. This is just one mic on the front lip, no equalization, fed into a Zoom H4N. The risers were almost 20 feet back from the lip of the stage. You can hear a lot of foot noise, and the boy's crying at the end was louder than their singing. I've always been impressed with the Bartlett, even one mic can sound like a complete mix.
Bartlett TM-125 on front of stage on Vimeo
Jim Andrada May 16th, 2015, 07:57 PM Yeah - they needed to sing louder!!! Not the mic's fault, of course! Piano was fine
Jon Fairhurst May 18th, 2015, 10:25 AM Thanks Warren,
I think the most impressive thing about your recording is the lack of noise at that distance. There are two main reasons for close mic'ing: 1) to isolate the sound, and 2) to get a high signal to noise. Your recording eases my worries about #2. :)
Jon Fairhurst July 23rd, 2015, 12:24 PM Last night, I did the first test of the Bartlett Stage Mic in a church auditorium. The results were mixed and hopefully can be improved.
The space is terribly reverberant. The audience space is about 70 feet long, 35 feet wide and 15 feet tall. All surfaces are parallel and reflective. There is a large beam about 15 feet in front of the stage that gives an additional early reflection.
The stage is about 2.5 feet up with front walls on the left and right, making it's own separate, smaller box (about 20x15x12). It's also reflective, but not as live as the main room.
Speaking loudly from the stage, one can hear a sort of "tuned feedback" even without a soundsystem!
For speakers, we purchased a pair of SRM450v3 powered speakers on stands placed wide and forward of the stage. The Mackies have built-in feedback suppression and we ran them with a flat EQ curve. With that setup, voices on the stage come through, but right at the verge of feedback. In fact, the energy one hears from the speakers tend to be those that excite the room. That's the sound the person speaking from the stage hears as well.
MY PLANNED SOLUTION is to build a "mic screen" in front of the stage mic. In theory, that will "stop" the energy from getting to the mic from the main room. Of course, energy that gets into the stage area can still get to the mic, but the smaller stage would be much cheaper to treat. Also, it doesn't seem to resonate at the same frequencies as the main room.
The "mic screen" needs a combination of isolation and absorption. I can build a hard shell for the audience side and stuff it with absorptive material on the stage side. Heavy wood (like MDF) would be easy to work with. Concrete might be better acoustically, but would be heavy and fragile. I have some 703 panels for a home project and figure that 4-inches of the stuff inside the half-shell, would make it fully dead.
From there, we can see about treating the stage area.
Any thoughts or recommendations?
Richard Crowley July 23rd, 2015, 01:59 PM The Bartlett Stage Mic is already cardioid. At best I would expect no improvement in rejection of sound from the rear, and at worst, a barrier may even make it worse by disrupting the back-side pickup pattern.
Frankly using barrier microphones like that for reinforcement is something I wouldn't even attempt. They are OK in some cases for recording. But I have zero expectations they would be useful for reinforcement. Good luck.
Sounds like your room has a natural resonance (your report of "tuned feedback" without the system on).
That means that the room needs NO reinforcement at that frequency, and you should filter out that frequency from the reinforcement system.
It also sounds like you have correctly identified some of the problematic reflective surfaces. I would have spent my budget on acoustic mitigation rather than barrier microphones.
Jon Fairhurst July 23rd, 2015, 04:31 PM Yeah, I knew that this was "challenging". We didn't expect much reinforcement, but we do get a bit. We spent around $200 for the single mic on a 20-foot stage. $200 wouldn't have scratched the surface of the treatment needed in this large space, so I'm happy with the direction we chose.
The speakers have feedback killers, but this room overwhelms them. In my quick living room test, it lit two of four LEDs. In the auditorium, all four are lit. It's maxed out. I could add a 1/3 octave EQ, but I'm afraid that I'd be chasing node after node. Kill one mode, nudge the volume, and the next node will resonate. Rather than starting flat and cutting problems, I'd probably want to start at zero and see which frequencies I can safely add. ;)
I still think the stage mic is our best bet. They will have a gaggle of 4 year olds on stage. Last year, people had problems hearing them. They're short, so they won't be far from the mic. :) Lavs were impractical and way over budget. Hanging mics would be farther from the "younglings" and would still present a feedback issue. A stage mic was our least bad affordable solution. And yes, it does help a bit.
The Mackies were a great choice. We could have stepped up to the 550s, but they weigh twice as much and cost more. The 450s have more than enough grunt and quality for this application - and one person can mount them on stands without injury. The feedback killer isn't a panacea, but it's simple, it helps, and it nearly came for free.
I'll give the mic shield a try. Yeah, the Stage Mic is spec'd as cardioid, but to be honest, I first set it up sideways and couldn't really tell which end was up from sound tests. I then turned the unit over and found the direction arrow. And yes, if the "bad sound" is eliminated from the front but not the back of the stage, I could be killing the cancellation signal while keeping the on-axis signal. Oh well, it won't hurt to try it. I might need to treat the stage to make the mic shield truly effective.
Such is life on a budget. With unlimited funds, we'd have an awesome space, high end lavs and transmitters for all the kids, a professional mixer, and enough wranglers to get the mics on the kids and then back in the equipment vault. For now, we'll made due.
Greg Miller July 24th, 2015, 06:23 AM From my past PA experience, I think it would not hurt you to notch out the worst two or three fixed frequencies. That would free up the adaptive filters on your speakers to work on some other frequencies, which might change from moment to moment.
Also, have you considered adding an outboard feedback eliminator? I had great success with some of the Sabine units. However, an external unit might interact with the adaptive filters in your speakers, so you might need to disable those if you're using something outboard.
And can you at least add a little absorption behind the kids? In other words, add it to the wall that the mic is pointed toward. That might help reduce reflection of the "room sound" off that wall and into the front of the mic.
Jay Massengill July 24th, 2015, 09:44 AM I agree with Greg. At a facility where I used to support a lot of meetings in its original configuration, I had to use a Shure external feedback reducer (connected to a computer for full functionality).
I probably achieved only 3 to 4 db more gain using the feedback reducer, but that made the difference between success and terrible sound.
People unfamiliar with this theater would step onstage during load-in and ask that the sound system mics please be turned down! Then I would tell them the sound system wasn't actually on yet... Freakish acoustics!
Over the years they replaced the orchestra pit cover with a much heavier, less resonant set. They added more acoustic treatment to the entire space, and then finally replaced the complete sound system with a much better one.
Jon Fairhurst July 24th, 2015, 10:37 AM I also considered an outboard feedback killer. That might make it into next year's budget, but I sure would want to try-before-buy.
One challenge is that the operators aren't technical. For Drama Camp next month, kids will be operating the mix, which will be four knobs for four sources (handheld solo mic, stage mic, keyboard, PC sound). I need as much as possible to be set-and-forget.
The previous system was very poor for the group. It was a Yamaha kit, including a powered mixer with many knobs and not much power. The speakers were small and underrated. They had already blown a speaker before I came onto the scene. There was no feedback killer. Adding an outboard unit while trying to explain Effects Send and Return wouldn't have worked. The first step after they turned that unit on was for them to say, "somebody get Jon cause I can't get any sound out of this thing." :)
Now, with powered speakers, EQ or an outboard feedback unit would go inline, so it might be more viable.
And yeah, I think the next step is to shield the mic from the front and treat the wall behind the actors. That should reduce the feedback from the hall both straight to the mic and after reflection. Hopefully, we'll get a few more dB of signal with that setup.
Paul R Johnson July 24th, 2015, 02:35 PM Just come to this again - and actually had (ironically) some shows with exactly this problem.
First thing, forget external feedback killers - to latch their filters onto a problem frequency you need to let the thing feedback. If you can do it in rehearsal, fine, but live, with no prep - they're hopeless. They also cut huge notches into the spectrum and they sound horrible. I have a pile in a rack somewhere that have not been used for maybe six years!
When you push the fader, and start to hear the ringing - if it's one frequency, then a tweak with sweepable eq is as far as you can go, and then that is the maximum that fader can go. This will be very gentle amplification, don't expect real volume.
I did a show with mainly kids and young adults - a dance show on the paperwork, but it was a dance AND song show, and the first time we heard them was the afternoon rehearsal. It took five minutes to put three cardioid boundaries out. One well balanced choir came up in volume nicely. However, all the ones where they really just didn't sing were awful. I could hear feet, I could hear fidgeting sounds but no voices. The organisers complained. Turning down the track they were whispering to made them sing even quieter. Turning it up made them sing a bit more, but the technically un-savvy teachers said it was drowning them out, so down it went again. In the end, I handed out 6 hand held radios and they had to use those. They damaged two!
There is no magic solution. Set and forget doesn't exist. You can get some conference systems that are very close to this but for shows, forget it. Unskilled performers and unskilled operators = disaster.
I felt sorry for a PA company who put in a 12 channel radio system for the school end of course show. The teachers got them to set it up, do the eq with the kids, and then they went. Instant bedlam - swearing from the dressing rooms, incessant feedback, totally awful mix. I was actually playing in the band and they panicked and asked me what they should do. I suggested they pay the guy from the PA company to work it for them. They could not see why they had to do this - after all, it was professional equipment and expensive to hire. I played, ignored the train wreck and went home. I would strongly advise NOT trying to shield the mic from the audience, you will wreck the way the boundary mic works. It relies on being on the big surface for it's gain and performance. A reflector behind it will make it even more prone to feedback. I built a housing to protect people from fallout from pyro pods, and it lowered the gain available from the boundary mic next door.
If the performers really don't produce much sound, then the mics will hear whatever is loudest, and this will be what you DON'T want to amplify.
With boundary mics, there is no point in a mega PA, because the gain before feedback won't even tickle it.
Stick a mic on somebody, or in front of somebody and the ratio between wanted and unwanted sound gets better. Any distant microphone of any kind is at a disadvantage, because it cannot select wanted from unwanted sound sources, it will hear whatever is there. Sadly, to get volume costs lots of money if the performers are the weak link.
Oh - and I broke one of the mini-XLRs after saying how good they were. I climbed down a ladder and my heel landed right on it. It didn;t break the mic socket, but snapped off the connector completely - leaving it in the socket!
Jon Fairhurst July 24th, 2015, 03:19 PM Great post, Paul. Nothing like practical experience!
Yeah, there are no silver bullets. I'll do as best as I can.
Regarding the boundary mic, I had it placed not far from the edge of the stage. Should I have moved it back? Is there a guideline for placement? Do we know what to expect as we move it from edge to center of the stage? If the shield is really dead (MDF + 4-inches of 703 fiberglass) and right at the lip of the stage, I'm not sure that it would impact the boundary effect.
One nice thing is that the stage surface is linoleum on concrete. It's solid and won't pick up creaking wood or resonant footsteps. Of course, we'll still get clothing noises and other rustling.
Note that we have a handheld cardioid for announcers and soloists, so we aren't totally dependent on the floor mic. It's an old Audio Technica that I bought 30 years ago and donated, along with a cheap Behringer mixer. I was worried that the mixer might add too much noise at high gains, but it hasn't been a problem at all. The Bartlett Stage Mic has a nice, strong output. I get feedback far before the noise is annoying.
Regarding the feedback destroyer, it's not terrible in this situation. Of course, it affects all sources, including music playback. Yeah, music sounded a bit funny, but the color from the destroyer is secondary to the color from the room. For our application, I'm reasonably happy with the results. It's no magic fix, but it helps more than it hurts.
This is a casual gig. Kids practice drama for a week in the summer. At the end of the week, parents and active church members attend the "big show". There are no curtains and no dramatic lights. Expectations are not high. But it's fun for the kids and heartwarming for the adults and their camera phones. There will be about 50-60 in the audience.
I think the system will give a bit of improvement from last year's "unplugged" event. Every dB helps. And it will be an opportunity to talk about the need for room treatment for the next budget cycle.
Paul R Johnson July 24th, 2015, 03:55 PM The stage we were using had a solid cover over the orchestra pit - nobody seemed to be actually dancing or standing on it, so we pushed the mics onto the edge of the 'real' stage, and gaffer taped them there, with cables going forwards to the stage edge. The problem with the barrier is simply that it produces a reflection from the sound source that arrives fractionally late and you get a comb filtering effect, that not only colours the sound, but creates peaks and troughs in the frequency response - making feedback worse. The PCCs are less sensitive at the rear, of course, which helps, but if you listen to them on PFL you can definitely hear the audience, although at reduced level. Sound from upstage, hitting the upright you use, adds to the stage pickup but not in a predictable way. We have tried PZM, PCC, short shotguns, flown omni and cardioids and none give you volume. On our stage we would use 3 or 5 PCCs, simply so one is always in the middle. If you bring up the centre one to just below feedback point, as soon as you add in the ones next door, the centre one has to come down, reducing it's level, add in the outer two and the others come down yet again. If you have one person centre, you can squeeze a bit more by taking the others out, but if it's a group of people spread across, then you just don't have the gain before feedback. Trying to mix these is an operational nightmare if you need every last dB. If the sound op has other stuff to do, then the only sensible operation is to find safe places for the faders and forget them
Rick Reineke July 24th, 2015, 04:43 PM W/O re-reading the thread, where are the PA cabs located? That can make a huge difference in feedback.
For the recording (if there is one), I recommend feeding the recorder with a pre or post fader send so cranking it for optimum record levels, would affect the house volume.
Yes indeed, Paul's reply is right on. +11
Jon Fairhurst July 24th, 2015, 05:15 PM Paul,
It's not clear how much boundary you recommend behind the mics on the audience side. Also, what is PFL?
And yeah, even though we're just using one Stage Mic (essentially a PCC-type design), we also get additional feedback by raising the levels of the handheld mics and even source music. A mic can add more feedback of course, but the source music will add more energy to the reverberant room, it builds up nasty notes, hits the mics, and away we go. Hopefully, the kid(s) who will do the mixing are sharp enough to learn how to twiddle the knobs smartly. (Many kids do great with computers and phones, so I might just get one who rocks it.)
Rick,
The speakers are on stands, placed wide in the auditorium. We were a bit cable limited with our first test, but moving them around and angling them differently didn't have much effect. From the stage, I didn't hear much direct radiation at all. I mainly heard the energy buildup in the room. I think the key will be to place the speakers as close to the audience as possible so they will be able to hear the direct sound at a low level. No matter where we place them, they act like "exciters" in the reflective room.
We won't do a recording this year, but if we were, I'd absolutely set it up pre-fader. I wouldn't want the recording volume to change while the mixer chases the levels just before feedback. I don't know that the little Behringer has a pre-fader send, but they'll need to upgrade that before long anyway. My Mackie VLZ-1402 does pre-fader, and that's roughly their next step for more inputs.
Greg Miller July 24th, 2015, 10:36 PM forget external feedback killers - to latch their filters onto a problem frequency you need to let the thing feedback. If you can do it in rehearsal, fine, but live, with no prep - they're hopeless.
With all due respect, IIRC that's not entirely accurate, at least with the Sabines we used. They have some filters that latched onto a fixed frequency. But they also have some filters that do not latch. As the talent was moving around with the mics, the mic-to-speaker distance changed, the ringing frequencies changed, and the Sabines kept up with everything just fine. With my experienced ears, I could hear a little ringing begin, then disappear. I doubt that many people in the audience even noticed that; it was certainly a lot less objectionable than uncontrolled feedback.
They also cut huge notches into the spectrum and they sound horrible.
I certainly wouldn't use them on a pipe organ or orchestra (not that either of these would require amplification anyway). I did not get the impression there were any "huge notches." The filters are much narrower than a 1/3 octave graphic. AFAIK, they were only notching out frequencies when they started to detect ringing.
I have a pile in a rack somewhere that have not been used for maybe six years!
Perhaps you could donate one to Mr. Fairhurst, and let him evaluate it in his venue! Or lend him one, and if it works for him, he can buy it with next year's budget.
When you push the fader, and start to hear the ringing - if it's one frequency, then a tweak with sweepable eq is as far as you can go
I agree with that. The room resonance is not going to change. If the mic is in a fixed location, the mic-to-speaker distance is not going to change. So you likely have a small number of fairly obvious peaks. Pull them down with a sweepable eq if you have one; if not, you can try to make do with a 1/3-octave EQ, but of course the results won't be as good.
And this is exactly what the Sabines do ... they have multiple automatic sweepable filters. Configure for a few fixed filters if you want, do the "gain raising" procedure to kill your fixed room resonances. They are much narrower and more accurate than a 1/3-octave graphic. Then the remaining non-fixed filters will chase any ringing that moves around in frequency.
Admittedly I think the OP is trying to make a silk purse out of a sow's ear, but while he may not end up with Gucci, with a little forethought and patience he may end up with something better than boot leather.
Paul R Johnson July 25th, 2015, 01:29 AM How odd, I had no luck with Sabines or Behringers because the problem is they have two basic modes, one where you can push the system a bit and then they'll find the problem quickly and notch it but the auto mode needs feedback to happen, and they don't detect ringing properly. They do, however, detect some instruments as feedback. Sustained guitar or perhaps a high sax note that doesn't move. They're too random. I treat one mic that is allowed to feedback as a mistake, and these gadgets are crude and unpredictable.
Jon - the Bartletts and the pcc160s that were popular before work quite well on the edge of the stage, with space behind them. The only distance issue is how far between them and the talent.
The feedback issue when you raise other faders is normal. As I said, increasing the number of open mics just makes things unstable. The floor mics are simply an unobtrusive useful mic, that's a bit more efficient on the floor than others.
PFL is pre fade listen,you can hear each microphone or other source before you fade it up. Indispensable for live sound, as hearing a toilet sound before you fade up a radio mic can prevent much embarrassment. I think most of us have made this mistake at some point!
It's very common for small fills to be used to give small areas of the audience coverage so the main, more distant speakers don't have to be aimed into areas that would leak back on stage.
Now we are using digital desks, multitrack recordings are now so easy. Simply plug in a USB cable to your laptop and hit record. All that messing around with cables has gone, thank god!
I doubt that kids will be able to do this. In many cases, in school stuff, the technical team are selected because they are not performers. This doesn't mean they have any abilities in technical operation. Some will simply be terrified to touch a fader! In my experience of education, dancers are often very good technical people as they know how to listen. I would give kids perhaps sound effects to trigger, and maybe a fader or two to add music. As for listening for feedback about to happen and reacting? I would consider that far too dangerous. Too hard for adults to do too sometimes. If the lights don't go out, nobody notices, a mic feeding back, and not being able to stop it kills the show. Doing it without at least one skilled person is crazy.
Greg Miller July 25th, 2015, 06:52 AM Mr. Johnson,
Indeed, it's very interesting that our experience differs. You mention the FBE latching onto sustained guitar notes, and maybe that's a clue. When I used them, I was using them only on vocal channels, and was not feeding any instruments (with their sustained notes) through them.
IIRC the depth of the automatic filters depends on the loudness of the ringing that's detected. So perhaps we weren't pushing our system very hard, the feedback was minimal, and the filter depth was minimal. I suppose if one cranks the gain up far enough, the filters will become very aggressive and then one might start to hear a lot of the problems that you describe.
Also, I note that Sabine now makes single-mic units, so that each mic gets its own processing. I never had the opportunity to try these, but it makes sense. So Mr. Fairhurst could use one of these on the floor mic, and one on the stand mic. That might work a bit better than one overall FBE on the mixer output.
And I certainly agree with your final comments about inexperienced operators. Playing video games does not necessarily prepare one for running PA. I remember running the PA system when I was in high school, and I certainly didn't have much of a clue about what I was doing back then. So good luck with kiddie techs!
Jay Massengill July 25th, 2015, 03:08 PM As I also stated, I had good success with the Shure FeedBack Reduction units I used.
They could operate as stand-alone units, but I usually connected a laptop (via the serial port) to them so I could see on the large screen what they were doing with the notch frequencies and depths and make manual adjustments as well. Saving and pulling up scene memories was also helpful. All this was done during setup and rehearsal, but the filters were free to adjust themselves slightly if needed during the show.
I normally assigned the vocal mic inputs (especially the problematic lavs) to a submaster which fed into the FBR.
The output of the FBR came back to a mixer input. None of the other "regular" audio sources ran through the FBR.
For recording I would use a post-fader aux send (that wasn't notched) on one recording channel of the program audio and a good ambient mic and preamp on the other recording channel that was isolated from the feed to the PA so it could never cause feedback no matter how loud I needed it set.
So I could set up independent levels for the individual inputs, and had independent control for the two or three main destinations on separate masters (PA, Recording, Telephone Send). Everything followed the normal live mixing of the individual faders, once all inputs were routed and main levels were set.
Jim Andrada July 25th, 2015, 06:12 PM Indispensable for live sound, as hearing a toilet sound before you fade up a radio mic can prevent much embarrassment. I think most of us have made this mistake at some point!
Or made the mistake of being the guy who used the toilet with an open mic. In Sydney. Got a huge hand when I walked out on stage. Mixed with all kinds of creative comments. Oh well, at least I had their attention.
Paul R Johnson July 26th, 2015, 06:04 AM The real snag (for me) is that when running at show levels with hand helds, then having a distinct single feedback frequency burst out when you were not prepared can be grabbed by the feedback processors reasonably quickly, but the burst was needed to kick start the process. The kinds of ringing and hollowness with distant miking doesn't sound like feedback - just a wider band extra component to the sound sources and the processors don't detect it as 'feedback'.
On the Behring X32, in one of the recent updates, the EQ screen now has a waterfall style overlay that shows were in the spectrum energy is, and it does make searching for and notching out spikes quite easy - I thought it a bit of a gimmick, but it's surprisingly useful. However, it also shows ringing is so low in level, it can't be seen, just heard, and I guess this disparity between full level and the ringing level is what stops the auto devices doing a good job, because there's always something in there that is louder and stopping the ring being detected.
The other thing with the auto devices is that zapping one loud feedback frequency usually starts another off, and then worst case, yet another. This sounds really bad. A much better solution is simply a quick finger, to drop the fader a little.
Greg (and please feel free to call me Paul) The guitar thing often happens when the backline leaks into the vocal mic, and it's a pain. In most cases, the lead vocal also has a bit of compression, which tends to make it worse. I do come across a few people who try to use them on the LR outputs, and this is even in some of the instruction books, but this is a dreadful way to work.
I'm actually on both sides of the mic, and in our tribute band (Beach Boys), my vocals often consist of one long sustained 'aaah' or 'ooooh', and that is also very bad news for the auto devices. We don;t use them, but I'd expect anyone who uses autotuned vocals would also trigger the filter.
If anyone is local to Great Yarmouth in Norfolk (the UK Norfolk) over the summer and wants to borrow one - I'll happily pull one out of the rack.
Jon Fairhurst July 27th, 2015, 11:04 AM I emailed Bruce Bartlett about my application and got a response over the weekend.
His top recommendation was treating the stage area with 703 or acoustic foam. The reflection from the stage is on-axis to the mic, so there is no in-mic rejection.
His second recommendation is to use a cardboard file folder in front of the mic to create a LF baffle. Add foam/insulation between the audience and file folder (but not touching the folder) to reduce mids and highs. This won't affect the polar pattern and might or might not increase gain before feedback. He recommended testing it as the "look" is cleaner if I don't need it.
He also noted that automatic feedback suppressors don't work well in his experience. He also recommends EQ.
The limitations make sense,
- Their notches are often too wide.
- They need stimulus before they kick in. (This is okay in rehearsal and for casual performances, but would not be acceptable in a pro setting.)
- False positives can cause them to suppress non-feedback tones.
- False negatives can cause them to miss lower level broadband feedback.
Yep. I get all of that. Then again, it still helps a bit. The main hall sounds so ugly that the uglification due to the feedback unit is secondary.
This past weekend, they had a Blueberry Pancake Breakfast there. An older guy with a hearing aid performed some gospel/country songs with a close vocal mic and gently strummed electric guitar using his own sound system. He ran some bizarre effects on his vocals that made him sound really thin. You could barely hear him sing. At some point he turned up the gain a bit and got some high-pitched feedback. I told him between songs, but the poor guy couldn't hear it. What was worse is that he walked off the stage to stand in front of the speakers. As soon as he got there, his body damped the sound and the feedback went away. Now he *really* can't hear it. Oh well, he turned it down a bit and the feedback went away. Yet another reason why the musician shouldn't be his own sound guy!
Paul R Johnson July 28th, 2015, 03:34 AM Interesting advice from Bruce. A foam baffle to reduce the mids and HF coming back into the rear of the mic from the audience side. Worth a try, but in most cases, that's not the path the PA speakers are taking to the mic when they feedback, they're being picked up from the sides, aren't they?
Jay Massengill July 28th, 2015, 07:57 AM Unless they are randomly facing the wrong direction, as I would often find the PCC-160's taped to the front edge of the stage in the local theater when I would visit during rehearsal week.
The sound mixer would usually say, "Ohhhh!, No wonder..." As in, "no wonder I wasn't getting anything worthwhile from that mic!"
Jon Fairhurst July 28th, 2015, 11:06 AM Yeah, when I first hooked up the Bartlett, I "pointed" it longitudinally at the actor's space. Then I looked at the arrow on the mic's bottom...
Regarding the direction of the feedback, the speakers were on the left and right sides and were pushed reasonably forward of the mic. (I'll push them even further forward with longer extension cords in hand.) But I found that I didn't hear much from them while standing on the stage. The venue is so live that you hear the room, not the speakers. The experience is not one of hearing yourself from the speakers. The experience is hearing the tones in the room that were excited by your voice from the speakers. Without a PA, the experience is similar, though a bit quieter. (I can't sing, but I can make the room sing!)
Greg Miller July 28th, 2015, 12:55 PM Jon, thanks for passing along the comments from Bruce Bartlett. I've never used a Bartlett mic, and I'm sure Mr. Bartlett knows what he's talking about so that should be useful information.
I can't quite visualize the file folder gag, but it sounds interesting. You said "in front of the mic" but do you mean "on the live side" or perhaps "on the dead [audience] side"?
Be that as it may, I am curious about his comment that the filters in feedback suppressors are too wide. I checked the specs for a few Sabine units and they claim 1/10 octave wide. Traditionally, bandwidth is specified at the -3dB point, and that would make the Sabines a lot narrower than a conventional 1/3-octave graphic. As I say, I'm not disagreeing ... just curious.
Paul R Johnson July 28th, 2015, 02:13 PM I suspect it's when they are trying to recognise ringing. This is not an individual tone but a cluster of individual notes spanning a quite wide range. My old symmetrix had variable width filters that closed u in width as the attenuation increased. I don't think the more modern units have this mode any longer. I mention feedback killers to a visiting engineer and he said they are as much use as a plastic hammer!
Jon Fairhurst July 28th, 2015, 06:49 PM I found the reference on Page 312 here under "Baffles Improve PCC Rear Rejection":
http://www.crownaudio.com/media/pdf/mics/memo22yr.pdf
(Lots of interesting reading at that link!)
This shows the mic on the folder. in the email, Bruce noted that having the file folder placed under the mic slightly degrades the mic's frequency response, so it might be preferable to turn it around. The key is having the vertical part between the mic and audience and allowing it to move freely.
Rick Reineke July 29th, 2015, 07:21 AM FWIW,
Bruce used to work for Crown.
Jon Fairhurst August 7th, 2015, 06:14 PM A quick update:
I set up the system for use in the Drama Camp next week. That same evening, the art director was there with a small crew (her family) constructing and rigging scenery. With more junk on the stage and in the room, the feedback problem was significantly reduced. It's still far from great though...
I ended up placing the speakers very wide in order to accommodate the needs of the space. I tried them with and without the feedback killer and ended up turning the FK off. I found it better to ride the gain just before feedback without the suppression as the initial ringing frequencies are also audible signal.
I tried the paper folder trick that Bruce mentioned, but there was no noticeable improvement in gain before feedback. I think the folder is more about isolating the orchestra pit. We don't have a pit. (We do have a community orchestra though. I play violin with them. But we aren't performing for this show.)
Here's a funny thing. My wife was near one of the speakers and said, "hey, this one's making noise." Turns out the stage mic was open and it was picking up the sound of a paintbrush ten feet back on stage. Hey, it works!
After I got everything secured with gaffers tape and all of the labels and default settings marked on our tiny mixer, the director's 14-year old daughter was bored, tired, and getting cranky. I asked her if she wanted to learn how to mix, and she absolutely lit up. The director came over to listen and learn as I taught the daughter.
There are just eight knobs for her to handle: gain for the Master, Stage Mic, Announcer's mic, Electronic Piano, and Laptop. Also, high, mid, and low EQ for the stage mic. Everything else is marked for a default setting. She quickly picked it up, we did some tests and she was able to ride the gain and EQ of the stage mic very nicely. By the end, she was like, "this will be my job all week!" She was beaming. At one point, her dad turned down the master when there was some feedback, and she said, "no Dad, this is the stage mic gain." Then she started to tell him about EQ...
She's got it handled. :)
|
|