why does a mic sound different every time?

[audiothings]

I don't understand it!

i have been a studio guy for over 10 years, but recently i have started to get involved with live sound...

we've done three shows and a tech rehearsal over the last three days, for a musical theater performance i am mixing, ... we are using the d-show profile, 12 head worn omis, and minus one tracks for this... gain is set with all faders at '0', and all settings are saved...

with the exact same settings, same levels and everything, one particular voice (that of our best singer/performer) is constantly confusing us... it sounds different every single time! during the tech rehearsal, it sounded perfect... almost equivalent to the studio reference tracks... we made the performer walk all around the stage, tuned the mic for the monitors and PA and there was no trace of feedback or hollowness or any other problem. but during the first show (i repeat, with the exact same settings), the voice became muddy and was constantly on the verge of feedback. So i had to cut a few frequencies to compensate, and though the show passed off okay, we were not happy. For the second show, we re-equalized the mic and it went off quite smoothly (tho' still not as good as the tech rehearsal). For the third show, we retained the settings, made the performer attempt to induce feedback at sound check and there was no problem... the first half of the show went off peacefully, but the second half was problematic again... very hollow sounding and very prone to feed back!

why is this happening?

note: the head worn mics were sent to their own group with 31 band eqs to tune out the general problematic frequencies, and each mic was further equalized to the particular performer's vocal situation.

[7rojo7]

were the tech rehearsals done with the whole group?
you have to ring out all the mics at the same time, that eq should only be used for the monitors as the FOH eq will be different.
Temperature and humidity can change the way sound is physically transmitted drastically.
there are many factors that could come into play
Sound check at 5 after a hot afternoon and show at 9 when everything starts to cool down
sound travels faster through humid air

[talbe1019]

I can think of one major change...audience.

[mixedupsteve]

What kind of mics were they and where were your monitors.
The first thought that comes to mind is that there were people in the house on opening night and that really changes the room/stage sound.

[equallyscrewed]

+1 for the audience changing it.

Also you've not mentioned if the different shows were at different venues (i think)

[vonrichter]

Originally Posted by equallyscrewed

+1 for the audience changing it.

+2. The entire acoustic situation changes when an audience is packed in. Other than that, maybe it's a Gremlin?

[hbphotoav]

Originally Posted by vonrichter

+2. The entire acoustic situation changes when an audience is packed in. Other than that, maybe it's a Gremlin?

+3 on the audience... a full dress rehearsal with a moderately full house is a great way to dial it in with a more similar acoustic...

and ditto on the need to ring all the headworns through a master group at the same time, or get it done at tech rehearsal where you can stop the show to fix EQ or mute cues or whatever. I do a couple of shows a year with 12-14 headworns (mixture of Countryman E6 and Gemini E6 knockoffs) and 2-4 lavalieres (Shure 184s) with a lot of swapping going on. "Hollow" can be phase interference with a close "other" mic, or it can be induced when the element on the (in my case) Countryman slips from the cheek to under the jaw.

My work is with kids in Broadway productions (the new "Peter Pan" was this spring's play) at a tone-y private school with dang nice audio budget. I have found that the adhesive bits from J&J "Flexible Fabric" BandAids (no other type I've tried works nearly as well, or hides as well under pancake makeup) left over when you cut them off the sterile pad, applied behind the ear (over the joint where the cable connects to the ear boom) and, if necessary, in front of the ear (dancers and folks with multiple costume changes) gives me three hours of serious adhesion. The mics don't move until they're removed... and the adhesives in front of the ear can be trimmed as needed to hide them as much as possible.

Another tip... if you don't have mic sashes on your main characters and dancers, buy or make them. Ours are denim pockets large enough to accommodate the old-style Sennheiser EW100 and Audix transmitters (and, of course, anything smaller)... the pouch is about the size of my hand... about 4x6 inches... and is sewn securely to lighter weight strips (24"-30") of fabric... cotton or linen work best... and tied in bows. Polyester is, as usual, a bit lacking in structural integrity. They're worn under the costumes, of course, and are a lot more secure than the stock belt clips attached to bra straps and biker shorts waistbands. The costume lady made us about 20 of them in less than an hour one afternoon, and we're 4 plays into their tenure with but a few minor repairs. Lots less expensive than ordering the velcro-closed sashes that Trew Audio stocks. HTH.

[John Willett]

You also have the fact that in a real performance the performer may be sweating more - could sweat be getting into the mic.?

[Thomas W. Bethe]

I work with voice over clients, I do recordings of operas and I work with live sound for musicals and I have to say that the human voice is NOT static and changes all the time. A slight cold, allergies, a sore throat, a stuffy nose and a heavy meal or drinking or consuming cream or milk can all change a person's voice. Also depending on their costume if they are wearing a lavaliere microphone or where they have the microphone placed on their lips if wearing a head microphone can make a fairly large difference in the sound of the microphone/voice. Also it has been my observation that NO singers ever sing the same in rehearsals as they do in concert or in an opera. They use a smaller voice for rehearsals and their normal voice when doing the show and it can be as much as a couple of dB hotter.

Couple that with the size of the audience and the difference in the humidity of the venue and you can have some fairly large swings in sound of the human voice. One other thing that needs to be mentioned is that hopefully you are using the same headset and the same belt pack every night for every performer since these can sound slightly different and can make a good sounding sound check into a marginal sounding show. We color code all our beltpacks and headsets/lavaliere microphones and assign that color to a given performer for the duration of the show.

Please let us know what you finally find is the problem....

[Don S]

Professionals, especially seasoned ones, will play or sing differently at a reh compared to a performance. I record and have played with professional orchestras for 10 years, in my experience, a concert fortissimo is usually about 6-8 db hotter than a reh or sound check. This is distantly miked for recording. I played Broadway for many years, and the sound guys knew just by listening who was a sub and who was the regular.

[bishopthomas]

Lots of good advice here but the simplest explanation hasn't been addressed: Are you absolutely sure that the microphones are being placed in the exact same spot every time? Are YOU the one attaching mics or is there a backstage person in charge of that? Or worse, are the actors responsible for their own microphone placement?

I'll also echo what Thomas Bethe said about using the same mic for each performer every night. I label each body pack with the character name and channel number and usually leave the mic attached. If you take the mic off the transmitter then a small label on the connector of the mic cable would be necessary. Just a quick tip for storage concerns: A hanging shoe bag is an excellent way to keep everything organized and tangle-free. Label each pocket so the packs always go in the same place to make it easy to see which actor threw his down backstage and went to the cast party.

[audiothings]

thank you all for the inputs so far.

were the tech rehearsals done with the whole group?

actually not. it was not even a real "tech rehearsal"... it is the local theater group's (fully licensed) adaptation of "Mamma Mia"

I grouped the head worns and tuned the group for FOH with an assistant walking around the stage and inducing feedback. Similarly I rang out each monitor pair (they were symmetric on each side of the stage) with its own 31 band eq.

then each performer came out and sang their most important song while I set up individual gains and eqs.

in this case however, the character in question is 'Donna', and the songs in question are 'The Winner Takes it All' and 'Slipping Through my Fingers'... both solo songs.

I can think of one major change...audience.

but audience should absorb frequencies, thereby reducing feedback...no?

What kind of mics were they and where were your monitors.

there were 4 countryman mics and 8 samson SE50 mics... believe it or not, we put the samsons on the important performers because we were able to get more gain before feedback from them!

Monitors were 3 sets of JBL 15" two way speakers with one set having subs... the subs were totally eq'd out for the singing portions... the portions where there was only dancing, we'd remove the eq and pump it up fully dry, for the dancers.

Also you've not mentioned if the different shows were at different venues (i think)

three shows, same venue. same 'Venue' console

One other thing that needs to be mentioned is that hopefully you are using the same headset and the same belt pack every night for every performer

yes, they were named and locked on the very first day.

Are you absolutely sure that the microphones are being placed in the exact same spot every time?

I can't be 100% sure, but the mic fit this performer perfectly and securely (others were having some fitting issues). And it seemed to be appropriately placed when i went to check on the problem. A little to the side of the mouth...

Thanks again and keep it coming...

[Jim vanBergen]

I've been mixing (and broadcasting, and taping, and post mixing) B'way shows for almost twenty years...

first: check the gear. Get the mics out to the console once they are powered up and LISTEN to the capsule. It's very easy for a capsule to become clouded with makeup, hairspray, cigarette smoke, and SWEAT!!! Once deposits get on the gold diaphragm, it will never sound the same again.

Compare the mic against the others. A/B every single element with your voice, and listen to low and high frequencies- hit consonants and vowels, and listen to the mics.

Does the model you're using have a capsule cover, like a Sennheiser MKE-2 or DPA 4061? Pull it off, wash it in warm soapy water, dry it, blow air thru it. Look at a light thru it to make sure its totally clean.

Next: make sure the placement is identical on the actor. A few millimeters closer or further from the skin is a HUGE difference in sound.

Have a talk with the performers about maintaining the exact placement of the mic, and covering the capsule any time they put on powder, hairspray, or anything that could get into the capsule.

You can't change the temperature and humidity in your part of the world, but you can talk to the theatre owners about trying to maintain a "show temperature". That would help. You also can't control the acoustics or the audience, so work on controlling and protecting the mic, and supporting the performers so you get consistent performances every time.

Hope this helps!

JvB

[llamaj]

audience absorbs some frequencies but reflects others. just like anything else that has this affect the audience is creating a boundry which can cause phase cancellation, feedback, etc.. after the audience clears out check the mics again.

[Storyville]

For head worn mics, even omnis, the audience shouldn't make that much of a difference. The majority of the sound is coming from the direct voice and the stage sound.

Positioning with omnis is really finicky. Proximity effect increases exponentially, and remember proximity effect extends the highs, not just the lows. An omni pickup pattern will also be more receptive to low end. So bare in mind that if the mic is head worn, you're probably within an inch of the speaker, which means even tilting the axis will have proximity effect to some degree. Lavelier mics can be hell because they change position as the shirt sags! Voices do change tone over the coarse of a day, but the tone should translate equivalently.

The one audience consideration is that people generate sound, even when they aren't talking. A bunch of people in the audience are generating a source of low end. If you notice mud showing up when the speaker faces the audience, that could be your problem. The feedback could be from compensating for the mud.

[audiothings]

Positioning with omnis is really finicky. Proximity effect increases exponentially, and remember proximity effect extends the highs, not just the lows.

wow! i thought omnis by definition have no proximity effect! how did i get it wrong?

[Thomas W. Bethe]

Originally Posted by Storyville

For head worn mics, even omnis, the audience shouldn't make that much of a difference. The majority of the sound is coming from the direct voice and the stage sound.

Positioning with omnis is really finicky. Proximity effect increases exponentially, and remember proximity effect extends the highs, not just the lows. An omni pickup pattern will also be more receptive to low end. So bare in mind that if the mic is head worn, you're probably within an inch of the speaker, which means even tilting the axis will have proximity effect to some degree. Lavelier mics can be hell because they change position as the shirt sags! Voices do change tone over the coarse of a day, but the tone should translate equivalently.

The one audience consideration is that people generate sound, even when they aren't talking. A bunch of people in the audience are generating a source of low end. If you notice mud showing up when the speaker faces the audience, that could be your problem. The feedback could be from compensating for the mud.

I don't think you have it correct

See

http://en.wikipedia.org/wiki/Proximity_effect_(audio)

Microphone Proximity Effect

DPA Microphones :: Directional vs. Omnidirectional Microphones

AKUSTYK for Praat

After a quick look I can not find ANY information on the WWW about the proximity effects of OMNI microphones. I can however find a lot of material on the proximity effects of cardioid and other "directional" microphones. Can you point me to where you got your information? Thanks!

[Roland]

Originally Posted by Storyville

For head worn mics, even omnis, the audience shouldn't make that much of a difference. The majority of the sound is coming from the direct voice and the stage sound.

Positioning with omnis is really finicky. Proximity effect increases exponentially, and remember proximity effect extends the highs, not just the lows. An omni pickup pattern will also be more receptive to low end. So bare in mind that if the mic is head worn, you're probably within an inch of the speaker, which means even tilting the axis will have proximity effect to some degree. Lavelier mics can be hell because they change position as the shirt sags! Voices do change tone over the coarse of a day, but the tone should translate equivalently.

The one audience consideration is that people generate sound, even when they aren't talking. A bunch of people in the audience are generating a source of low end. If you notice mud showing up when the speaker faces the audience, that could be your problem. The feedback could be from compensating for the mud.

I'm sorry Storyville, but most of what you havea written above is rubbish. The whole thing about omni's is that they don't exhibit proximity effect. The OP also stated that these mics were head worn which you mention in the start of your post, then you move to talking about body worn lav's. The audience generating low end even when they are not talking is also totally misleading, the audience isn't generating much low end at all even when laughing, you don't believe me, go take a rta meter in there and take the measurement. Also most lavs don't respond that well down there and even those that do it is standard practice to have HPF in circuit probably with quite a lot of bass cut.

To the original poster, Lav's can sound different for a number of reasons, position on the talent relative to their mouth, sweat, temperature, humidity, makeup in the grill, different ageing/contamination of mic elements and the way the talent sings/talks that particular show.


Regards


Roland

[John Willett]

Originally Posted by audiothings

wow! i thought omnis by definition have no proximity effect! how did i get it wrong?

You didn't get it wrong - you are absolutely correct - omnis do *not* have proximity effect.

[Welkin]

The thing about audience is that it absorbs reflections and produces noise which both require compensating with higher levels and use of more reverb. Did you calibrate the system in the tech rehearsal so that you know if you are getting louder sound in the performances? The feedback can be caused by a reflection of a monitor from a wall or something that didn't cause problems in the tech rehearsal because the singer was standing in a slightly different position or the sound level was a couple of dBs lower. Was the set ready in the tech rehearsal? It's surprising what a good coat of paint can do to reflections. The change in sound is propably caused by makeup and sweat or a slight change in the position of the mic as was already suggested.