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Author Topic: Acoustic treatment alternatives  (Read 11231 times)

Greg_Cameron

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Acoustic treatment alternatives
« on: October 17, 2011, 02:02:51 am »

I have been told by several people "in the know" that one of the best ways to go these days with acoustic treatment is eco insulation since it's sound absorption properties are outstanding and it's non-toxic to work with unlike fiberglass. Frame it up and use Guilford FR cloth for covering and you're good to go. At the venue I work in, we've done complete surface measurements and figured that the ballpark for raw materials is around the $16k range just for the insulation and Guilford. There are of course other costs for wood & labor, etc. I was wondering if there might be a lower cost alternative out there that might be effective as well for acoustic treatment. Any thoughts?

Thanks,
Greg
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Brad Weber

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Re: Acoustic treatment alternatives
« Reply #1 on: October 17, 2011, 07:11:30 am »

I have been told by several people "in the know" that one of the best ways to go these days with acoustic treatment is eco insulation since it's sound absorption properties are outstanding and it's non-toxic to work with unlike fiberglass. Frame it up and use Guilford FR cloth for covering and you're good to go. At the venue I work in, we've done complete surface measurements and figured that the ballpark for raw materials is around the $16k range just for the insulation and Guilford. There are of course other costs for wood & labor, etc. I was wondering if there might be a lower cost alternative out there that might be effective as well for acoustic treatment. Any thoughts?
"Acoustic treatment" doesn't really define what you're trying to do or what the material needs to do and just randomly throwing materials up as "acoustical treatment" may affect the room acoustics but not necessarily in the most effective or desirable manner.  Are there any specific acoustical properties that you are looking to obtain?  Are you looking at absorption only or also at diffusion?  If for absorption, are you just looking for 'soft stuff' or are you looking for something that offers specific absorption at certain frequencies?  Are you looking for a certain thickness or density?
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Greg_Cameron

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Re: Acoustic treatment alternatives
« Reply #2 on: October 17, 2011, 10:26:28 am »

"Acoustic treatment" doesn't really define what you're trying to do or what the material needs to do and just randomly throwing materials up as "acoustical treatment" may affect the room acoustics but not necessarily in the most effective or desirable manner.  Are there any specific acoustical properties that you are looking to obtain?  Are you looking at absorption only or also at diffusion?  If for absorption, are you just looking for 'soft stuff' or are you looking for something that offers specific absorption at certain frequencies?  Are you looking for a certain thickness or density?

We're looking to deaden the room as much as possible, period. The idea was to apply damping materials to almost all surfaces except for the floor. The most problematic frequencies in the room are in the 400-500Hz range. But really it's necessary to squelch everything above that as well. So complete coverage of the ceiling & all walls was goal to really mitigate the RT60 across a broad spectrum and I was told the eco insulation was great for this. The floor will still be a reflective surface regardless, but it would be nice to have only the one bounce an then have all the other surfaces soak it up. The room isn't totally horrible and usually sounds decent if/when it's packed with warm bodies. But if it's a lightly attended show, the room does cause intelligibility issues with vocals.

Greg
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Tom Williams

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Re: Acoustic treatment alternatives
« Reply #3 on: November 16, 2011, 05:43:09 pm »

What shape is the room? Is it a square box? Tier levels etc...? Full coverage usually isn't required, or aesthetically pleasing.

Please excuse me if this sounds condescending, are the tops pointing where they need to be? Are they flown? You need to get the best
coverage possible out of the system before you think about treatment.

I like the idea of the Eco insulation panels, maybe you could try some corner bass trapezoids. The best thing about DIY acoustic paneling is you can build and test as you go.
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Greg_Cameron

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Re: Acoustic treatment alternatives
« Reply #4 on: November 18, 2011, 12:18:44 am »

What shape is the room? Is it a square box? Tier levels etc...? Full coverage usually isn't required, or aesthetically pleasing.

Please excuse me if this sounds condescending, are the tops pointing where they need to be? Are they flown? You need to get the best
coverage possible out of the system before you think about treatment.

I like the idea of the Eco insulation panels, maybe you could try some corner bass trapezoids. The best thing about DIY acoustic paneling is you can build and test as you go.

Hi Tom. Yes, the tops are pointing where they need to be. Coverage isn't the issue. it's intelligibility and mainly when the room isn't full of bodies. Once it's full, the problems clear up pretty well but there's also too much stage bounce off the ceiling that needs to be mitigated.

As far as bass traps go, low end isn't the issue. The problem area is in the 400-500Hz range as stated previously. If you're interested in checking out the room, pics are here:

http://www.cameronproaudio.com/owhallpics.zip
 
The subs aren't in those pics, normally the stage looks like this:


Greg
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Tom Young

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Re: Acoustic treatment alternatives
« Reply #5 on: November 18, 2011, 07:21:58 am »

If you're interested in checking out the room, pics are here:

http://www.cameronproaudio.com/owhallpics.zip
 
The subs aren't in those pics, normally the stage looks like this:


Greg

I think you may have another far more serious issue here: the rigging safety of the FOH loudspeaker clusters.

I am not an experienced theatrical rigger nor a licensed structural engineer, but I have hung lots of clusters, etc. and have worked with these other specialists. This looks wrong.

Before you go any further you should have this rigging system inspected and stamped by a licensed structural engineer.

Really.
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Greg_Cameron

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Re: Acoustic treatment alternatives
« Reply #6 on: November 18, 2011, 10:09:27 am »

I think you may have another far more serious issue here: the rigging safety of the FOH loudspeaker clusters.

I am not an experienced theatrical rigger nor a licensed structural engineer, but I have hung lots of clusters, etc. and have worked with these other specialists. This looks wrong.

Before you go any further you should have this rigging system inspected and stamped by a licensed structural engineer.

Really.

Tom, the rigging was designed by Dave Rat in conjunction with ATM and the bumpers are designed to hold 8 boxes (1 ton) each with a greater than 5:1 safety factor. There is also steel backup for the nylon straps used to hold the boxes to the bumper and the fly tracks. These bumpers were used for world tours by some of the biggest rock acts in the world for over a decade. I'm not a dummy and I would never allow anything to be flown over people's heads improperly.

The ceiling/roof truss was given the thumbs up by structural engineer as well before flying. The building is a 150 year old historic building, a foundry and machine shop where they used to build most of the mining equipment for the gold rush. Multi-ton iron beams used to be suspended from that truss for holding hoists to lift heavy iron equipment with snow on the roof. A 500 lb. load on each side of the stage is a walk in the park. And the wire rope used to hold the bumper is 3/8" which is way overkill. All wire rope used is rigging certified and purchased through a reputable rigging shop. If you see something improper though, by all means point it out.

Greg
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Greg_Cameron

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Re: Acoustic treatment alternatives
« Reply #7 on: November 18, 2011, 10:14:15 am »

FWIW, this is the rig the system came from:

http://ratsound.com/systempics.html

Greg
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Brad Weber

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Re: Acoustic treatment alternatives
« Reply #8 on: November 18, 2011, 01:06:26 pm »

Coverage isn't the issue. it's intelligibility and mainly when the room isn't full of bodies. Once it's full, the problems clear up pretty well but there's also too much stage bounce off the ceiling that needs to be mitigated.

As far as bass traps go, low end isn't the issue. The problem area is in the 400-500Hz range as stated previously.
The fact that the problem is lesser when the room is full could be related to a number of factors.  It could simply be the amount of absorption the crowd represents and adding other absorption may help with that.  However, it could also be the fact that the people cover the floor, the acoustical diffusion the crowd also represents, the changes in humidity and temperature that may occur or some combination of all of these.

One simple reality is that few spaces actually come that close to being true reverberant spaces, thus where any absorption or other acoustical treatment is located can matter.  Putting soft stuff on the walls and ceiling may not have the same effect as putting it on the floor as they crowd is even if the same amount of absorption is added.

Along with cost, a couple of common factors for acoustical treatments are appearance and durability.  A spray-on treatment like K-13 from International Cellulose may provide a lot of 'bang for the buck', especially in a larger, open, flat floor space since it is easier to install in those.  It can be tinted and is available in black.  But it is also not typically acceptable as a visible finish in a high finish space nor is it something you necessarily want installed where it will be run into or people can pick at it.

2" or thicker duct liner or Select Sound fiberglass board from Owens Corning are also often cost effective options where you want a black finish.  Covering them with hardware cloth or similar improves the durability, but unless you are going for an industrial look then they may also not present the appearance you want and they can be damaged.

Either the spray on or fiberglass board options might be cost effective for the ceiling treatment.  If durability is a concern down at crowd level then they will cost more but something like these, http://www.kineticsnoise.com/interiors/pdf/knp.pdf, http://www.kineticsnoise.com/interiors/pdf/ksp.pdf and http://www.industrialacoustics.com/usa/downloads/absorption%20panels/Varitone%20prod%20lit.PDF are used in gyms, natatoriums, industrial spaces and correctional facilities.

And with all of these you need to make sure the Flame Spread Index and Smoke Developed Index meet the applicable requirements for use in a public assembly space.
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Greg_Cameron

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Re: Acoustic treatment alternatives
« Reply #9 on: November 18, 2011, 06:57:21 pm »

Along with cost, a couple of common factors for acoustical treatments are appearance and durability.  A spray-on treatment like K-13 from International Cellulose may provide a lot of 'bang for the buck', especially in a larger, open, flat floor space since it is easier to install in those.  It can be tinted and is available in black.  But it is also not typically acceptable as a visible finish in a high finish space nor is it something you necessarily want installed where it will be run into or people can pick at it.

Thanks Brad for that link to the K13. That looks very interesting. Could be good for the ceiling for sure. Good coefficients at the problem frequencies. Any idea what something like that costs for 3" thick per sq. yard?

I looked at the various Dow Corning solutions and they are actually fairly pricy when compared to denim UltraTouch R-13 insulation combined with FR701 cloth. So if we go with a panel based solution, it will likely be the UT R-13 & FR701. So far cost wise there's nothing close.

Greg
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Re: Acoustic treatment alternatives
« Reply #9 on: November 18, 2011, 06:57:21 pm »


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