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Author Topic: Floor reflections in live situations  (Read 2268 times)

Fifthcircle

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Floor reflections in live situations
« on: November 17, 2007, 11:13:01 PM »

I hope this is an ok place to post this question.

I do a lot of live classical recording on location.  As a part of the job, I often have to place microphones in locations that aren't exactly perfect due to aesthetic considerations.

I have a relatively new client where I absolutely must have my microphones as close to the floor as possible (It is opera and there are sight-line/aesthetic issues with microphones).  To do this, I have my mics on small (4-5") stands.  The biggest problem with this is the reflections off of a hard stage floor can really affect my sound.

To get around this, I've taken some generic foam and felt and placed it under the mics.  It usually succedes in taking a bit of the bite (high end) off of the sound in the mics which is a good thing.  I'm sure, however, that there are better acoustic products out there for the job.  Basically, I need a low-profile black absorptive surface to place below each of the microphones.  It can be up to about a square foot in size.

Anybody have ideas of what I could use that would work for this?

Thanks!

--Ben
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Benjamin Maas
Fifth Circle Audio
Los Angeles, CA
http://www.fifthcircle.com

brett

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Re: Floor reflections in live situations
« Reply #1 on: November 18, 2007, 05:25:02 AM »

semi-rigid fiberglass cut into small squares and covered with fabric to match the stage.
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franman

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Re: Floor reflections in live situations
« Reply #2 on: November 18, 2007, 10:57:43 AM »

IMO, the use of 3-4" thick Dark Grey acoustic foam is probably your best bet.. it's easily transported, inexpensive and you can purchace more as it gets beat up. There is a black rigid insulation product that is available from a number of sources that could be used instead. A total of 4" would provide an NRC near 1.0 and absorb well down 250Hz or a little lower. See the attachment... having said all that, I would still probably use acoustic foam...best of luck.

oh yeah, one more thought.. Boundary microphones?? How about giving these a try? You can put em right on the floor.. they will have a hemispherical response that should be reasonbly flat...just a thought.
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avare

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Re: Floor reflections in live situations
« Reply #3 on: November 18, 2007, 12:02:48 PM »

Franman gave the word.  Boundary mics.  There is a whole ton, no, two tons, of companies selling them.

Andre
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Fifthcircle

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Re: Floor reflections in live situations
« Reply #4 on: November 18, 2007, 03:38:15 PM »

Boundary mics aren't going to work for a host of reasons...  The biggest being the lack of directionality.  When you have people 15 feet upstage of your mics, you need dig.  A hemispherical pickup simply does not give that.  On the directional front, there are 2 mics that could work- the Crown PCC160 and the Sanken CUB-01.  The Sanken sounds pretty decent, but has absolutely no low end (as it is made for recording dialog in the film world) and the PCC just sounds bad.  I own one sanken, but positioning was difficult when I tried to use it.

I'm using Schoeps Cardiods for the gig as I get fidelity of the voices as well as dig upstage.

I think an acoustic foam will likely work best.  A 4" thick chunk of fiberglass may be looked at poorly by the directors of the opera.  Heck, the 2 inches of height of my stands from the Atlas Quick release that I use was frowned upon...

Does anybody have a suggestion as to what to look for with acoustic foam.  I'm not as concerned about low frequency reflections as the majority of the low frequencies come from the pit- not the stage (the stage is pretty much vocal only).

Thanks for your help so far...

--Ben
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Benjamin Maas
Fifth Circle Audio
Los Angeles, CA
http://www.fifthcircle.com

gullfo

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Re: Floor reflections in live situations
« Reply #5 on: November 19, 2007, 12:45:53 PM »

could a figure-8 mic be used and put the absorption near (not too near) the back side? they have a high degree of side rejection which might eliminate the near-floor reflections and still be wide enough to get near vox and upstage.

http://www.schoeps.de/E-2004/figure-8.html
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Glenn Stanton

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Fifthcircle

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Re: Floor reflections in live situations
« Reply #6 on: November 19, 2007, 01:04:25 PM »

Hmmm... Interesting thought.  I have also considered using hypercardiod mics as well, but I don't own enough of them.  My big concern in that case is more the narrow pickup than the floor reflections...  Perhaps a hybrid approach, though, may work.  Something to think about.

--Ben
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Benjamin Maas
Fifth Circle Audio
Los Angeles, CA
http://www.fifthcircle.com

jetbase

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Re: Floor reflections in live situations
« Reply #7 on: November 19, 2007, 09:12:20 PM »

Hi Ben,

The most versatile product I've found (which Greg Simmons put me on to - I assisted yourself & Greg at the Sydney Opera House once) is Tontine Acoustisorb. It's medium grey in colour, so you would have to either cover it in black fabric, or I bet you could just spray paint it. I mostly use 4" thick, but 2" thick is quite useful as well. The only thing is I'm not sure if it's available outside Australia, or whether it would be under another name. Anyway, it's much safer and easier to use than fibreglass & more durable than foam. Without looking at specs it seems to be better absorption than both.

http://www.fibres.com.au/Data-Sheets/Acoustisorb/Acoustisorb -Performance-Graphs.asp

Glenn
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