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post #10381 of 10427 Old 07-11-2014, 09:22 PM
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Originally Posted by badger985 View Post
I was looking to make corner bass traps, and was going to buy Owens Corning 703 and cut them into the correct dimensions, however when doing research I found the following

Owens Corning "Select Sound" Black Acoustical Board 2" inch thick has an NRC of 1.00 the same as 703, but it also states that this reduces sound reverb, which 703 does not. Would this be a better product to create Bass Traps out of?

To answer your last question first "Would this be a better product to create Bass Traps out of?"
No.
Please see: http://www.bobgolds.com/AbsorptionCoefficients.htm
look for 703, and compare it against Black Acoustic Board at {125hz, 250hz, 500hz, 1000hz, 2000hz, 4000hz}
There are lots of things very similar to 703, and anything that's similar is just fine.


The 'reverb' comment just seems odd to me. Either used correctly should take care of reverb. Either used insufficiently will not take care of reverb. A myriad of other things can be used to take care of reverb.

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post #10382 of 10427 Old 07-11-2014, 09:32 PM
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Originally Posted by coolgeek View Post
I am looking to build a gentle diffusion.. and was thinking of using those 'vinyl tiles' that people use for flooring would work?

Do the vinyl absorb the sound or reflects them? If they absorb, then it won't work.

I was thinking of getting those and then bend them to semi-round... it's easy to build.. just put a bunch of them in right angles, bent into half round shapes...

Basically something like below (contour type diffusers) but built out of vinyl floor tiles rather than wood:



Vinyl will reflect some frequencies (higher f), and transmit (through it) other frequencies (lower f).
Generally speaking, anything more solid than 1/8" Masonite is ok as a diffuser.


The frequencies it has a hope of diffusing are proportional to the size of each.
The rule of thumb is:
- at wavelengths significantly smaller than the object, get defused as light bouncing off a curved mirror.
- wavelengths significantly larger than the object, ignore the object
- wavelengths the same size as the object, reflect randomly.


With all of these being identical, spaced identically, you might get lobbing effects. Random sizes with random placement, give better diffusion.

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post #10383 of 10427 Old 07-12-2014, 09:30 AM
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Originally Posted by BasementBob View Post
To answer your last question first "Would this be a better product to create Bass Traps out of?"
No.
Please see: http://www.bobgolds.com/AbsorptionCoefficients.htm
look for 703, and compare it against Black Acoustic Board at {125hz, 250hz, 500hz, 1000hz, 2000hz, 4000hz}
There are lots of things very similar to 703, and anything that's similar is just fine.


The 'reverb' comment just seems odd to me. Either used correctly should take care of reverb. Either used insufficiently will not take care of reverb. A myriad of other things can be used to take care of reverb.
Great Thanks.

Just to clarify the 703 FRK only has the foil reinforced on one side, thus if I slap that together with a regular piece of 703 2" to create a 4" trap, I will still get the benefit of the Foil Craft, and the enhanced Sound absorption at 125hz?

Thanks again.
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post #10384 of 10427 Old 07-12-2014, 12:37 PM
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Originally Posted by badger985 View Post
Just to clarify the 703 FRK only has the foil reinforced on one side, thus if I slap that together with a regular piece of 703 2" to create a 4" trap, I will still get the benefit of the Foil Craft, and the enhanced Sound absorption at 125hz?

Skip the FRK/foil. Membrane absorbers require an expert. If you understand how to make a membrane absorber, and how to measure/calculate the effects of existing wall resonance on the membrane, you're better than me. If you measure and discover you need a tuned membrane absorber to deal with a pesky room mode, look at a professional one like RPG Modex.


Mineral wool (including fiberglass), and corner traps, of just mineral wool and acoustically transparent cover fabric, are idiot proof.


1) soundproofing is good
2) knock first reflections down by at 20dB
3) deal with room modes. Minimalist techniques include tri-corner traps and subwoofer placement.
4) no chairs higher than your shoulders
5) wide frequency absorption, not high frequency absorbers

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Last edited by BasementBob; 07-12-2014 at 12:46 PM.
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post #10385 of 10427 Old 07-14-2014, 12:19 PM
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Can someome give me a quick layman's explanation of what corner bass traps do - or help with - with the sound of the room? Does it reduce "boom" in the room? Anything else? Also, I imagine, if these are added to a room, you would probably have to re-run Audyssey XT32, correct?

Thanks!
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post #10386 of 10427 Old 07-14-2014, 12:50 PM
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Any acoustic treatment to a room warrants Audyssey to be re-run.

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post #10387 of 10427 Old 07-15-2014, 05:25 AM
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Quote:
Originally Posted by bambam View Post
Can someome give me a quick layman's explanation of what corner bass traps do - or help with - with the sound of the room? Does it reduce "boom" in the room? Anything else? Also, I imagine, if these are added to a room, you would probably have to re-run Audyssey XT32, correct?

Thanks!
Bass Trapping will help with low end nulls and peaks, but also it will help with low end decay (think of this like reverb). If the low end decay is under control then the bass will be clearer and have much more punch. See the following video.
http://www.gikacoustics.com/video_bass-traps/
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post #10388 of 10427 Old 07-16-2014, 01:41 AM
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Quote:
Originally Posted by bambam View Post
Can someome give me a quick layman's explanation of what corner bass traps do - or help with - with the sound of the room? Does it reduce "boom" in the room? Anything else? Also, I imagine, if these are added to a room, you would probably have to re-run Audyssey XT32, correct?

Thanks!
Hi bambam,

Yes, it is highly recommended for you to re-run the Audyssey calibration after altering/improving your room's acoustic characteristics. Otherwise Audyssey will be attempting to make corrections for issues that either no longer exist or have been greatly changed -resulting in less than an optimum result from your acoustic improvements.

Cheers
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post #10389 of 10427 Old 07-16-2014, 09:48 AM
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Originally Posted by bambam View Post
Can someome give me a quick layman's explanation of what corner bass traps do - or help with - with the sound of the room?
Superposition of waves: net amplitude caused by two or more waves traversing the same space is the sum of the amplitudes which would have been produced by the individual waves separately.

In a room, sound waves are created by speakers. The sound bounces off hard surfaces like walls, ceilings, and floors; resulting in superpositions with subsequent waves coming from the same speaker(s) tiny fractions of a second later.

Of the various reflective interference situations, one is 'room modal resonance'.
When the sound frequency's wavelength is an integer multiple of the room length, the reflected wave superpositions are in resonance (in phase), and build up to extremes.
Extremes that can eliminate a frequency at some spots in the room (nulls) and quadruple the volume of that frequency at other spots in the room (peaks).
Thus, two people sitting side by side, one might not hear a frequency at all (sitting in a null) and the next might find it booming (sitting in a peak).





Although most reflections (other than room modal resonance) tend to be multiple angles like lasers off mirrored walls; the sound waves that make up axial modes (the primary room modal resonance) quickly settle down into back-front, or left-right, or up-down, directions. The room mode reflection is across the entire surface of the reflecting/opposing pair of walls (or floor/ceiling).

Corner traps have a couple of bits of physics and dollars in their favour
a) the diagonal shape of a corner trap uses little human usable space, yet is deeper than most wall absorbers are likely to be, that depth increasing the low frequency absorption
b) because its on a corner, it's involved in at least two axial modes directions (e.g. a vertical corner would affect the left-right and the front-back axial modes). Thus you're affecting multiple directional problems with a single purchase.
c) if you build the corner trap to completely fill the corner, then at least some of it is in a tri-corner (wall and ceiling and floor) thus hitting all three axial mode directions (up-down, left-right, front-back).

So, what you're trying to do with corner traps is knock down the strength of the reflecting wave at each reflection, thus reducing the resonant/superpositioned peaks and nulls, evening out the sound at more seating locations in the room.

Here's what a room looked like before corner traps

and here's what it looks like after corner traps
Notice the reduction in peaks in the 30hz to 200hz range.


Here's a waterfall version, before corner traps

and after corner traps
Notice the reduction in the bottom axis. This represents a reduction in the time the sound is active in the room,
aka a reduction of the 'ringing' time/duration at that frequency,
caused by the corner traps absorbing a bit of each reflection.


Because mineral wool (including fiberglass) porous absorber corner traps tend to be broadband absorbers (multi frequency) they automatically hit whatever modal frequencies happen to hit them.

A tuned membrane absorber, on the other hand may waste a corner -- because its absorption is aimed at a specific single room mode (e.g. a front-back resonance), but multiple modes are active in corners (e.g. front-back and left-right), the space used by the tuned membrane absorber means that you can't simultaneously use the same space for treating other room modes (e.g. left right).

The frequencies of room modes can be somewhat predicted using a room mode calculator, that translates the integer multiple wavelengths based upon the room dimensions. e.g.
http://www.bobgolds.com/Mode/RoomModes.htm

I say 'somewhat' because walls are not perfect reflectors, so the frequencies tend to be near these, but not exactly. You can't tell until the room is built and full of stuff what needs to be treated.


http://forum.studiotips.com/viewtopic.php?f=8&t=536

superchunk


corner absorber
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Last edited by BasementBob; 07-16-2014 at 01:15 PM.
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post #10390 of 10427 Old 07-16-2014, 10:02 AM
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Problem is that the graphs show pressure and you really want to put that effort into where you have the maximum particle movement in the air, and those graphs are opposite. So the corner traps have to be big to expand enough out into the room to start having an effect on anything that's reasonably low. If you DO need pressure based absorbers, then corners are THE place for those. ( For particle movement, a heavy drape hanging a foot from the wall might be more efficient perhaps?)

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post #10391 of 10427 Old 07-16-2014, 12:03 PM
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Hello,

I am at the point where bass traps are next on the build list... Will cutting a 2X4 sheet of OC703 into 16 triangles and stacking them in the corners of the screen wall be OK?? Reason I ask is because my screen wall only has a 12 inch clearance behind it.

Thanks in advance!
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post #10392 of 10427 Old 07-17-2014, 05:20 AM
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Originally Posted by xzener View Post
Hello,

I am at the point where bass traps are next on the build list... Will cutting a 2X4 sheet of OC703 into 16 triangles and stacking them in the corners of the screen wall be OK?? Reason I ask is because my screen wall only has a 12 inch clearance behind it.

Thanks in advance!
Having the fiberglass in those corners should be fine, if I am understanding your question correctly. Basically all corners are good to use for bass trapping.

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post #10393 of 10427 Old 07-17-2014, 09:35 PM
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Originally Posted by Ethan Winer View Post
JB,

I agree with Dennis that B is wrong. I'll go even further and say you should never cover any large surface area with material that absorbs the mids and highs. It makes the room too dead sounding, and does nothing to solve the inevitable low frequency problems. Much better is a mix of bass trapping and mid/high absorption, with no one area all live or all dead.

--Ethan
I've only heard of absorption, reflection and diffusion, what's this "Bass Trapping" nonsense? You aren't trapping any bass frequencies, either you are absorbing it or you aren't. Diaphragmatic membrane absorption systems work best for low frequencies below 100Hz, but they aren't "trapping" the bass frequencies, it's just another more effective way to absorb and control the bass, since typical midrange/high frequency absorption products don't work for the low frequencies under 100Hz, they work better for 125Hz and above, depending on the product and it's absorption curve.

Why people are so fixated on the words "bass trap" is more of a marketing term, it's kind of annoying.
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post #10394 of 10427 Old 07-17-2014, 11:31 PM
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Originally Posted by drblank View Post
I've only heard of absorption, reflection and diffusion, what's this "Bass Trapping" nonsense? You aren't trapping any bass frequencies, either you are absorbing it or you aren't. Diaphragmatic membrane absorption systems work best for low frequencies below 100Hz, but they aren't "trapping" the bass frequencies, it's just another more effective way to absorb and control the bass, since typical midrange/high frequency absorption products don't work for the low frequencies under 100Hz, they work better for 125Hz and above, depending on the product and it's absorption curve.

Why people are so fixated on the words "bass trap" is more of a marketing term, it's kind of annoying.
What category would you place a tuned helmholz resonator into?

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post #10395 of 10427 Old 07-17-2014, 11:37 PM
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What category would you place a tuned helmholz resonator into?
Another form of low frequency reduction. It works on a different principal to reducing low frequency pressure in a room than a diaphragmatic membrane absorption system. They are both used in dealing with low frequencies, but they work differently. Diaphragmatic membrane can be either tuned to a specific frequency range or they can be designed for more broadband low frequency depending on materials used and design.
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post #10396 of 10427 Old 07-18-2014, 03:45 AM
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If you would like, you can read more about different kinds of Bass TRAPPING (ha ha) here.
http://www.gikacoustics.com/understa...bass-trapping/

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post #10397 of 10427 Old 07-18-2014, 10:28 AM
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Why people are so fixated on the words "bass trap" is more of a marketing term, it's kind of annoying.
The term bass trap has been used as far back as at least 1974, and probably even earlier, as you'll find in this back issue of dB magazine:

http://www.americanradiohistory.com/...DB-1974-09.pdf

Absorbing and trapping are basically the same thing. A mouse goes into a mouse trap and doesn't come out. Same for the Roach Motel. And again the same for bass entering a bass trap.

To call bass traps "nonsense" sounds more like trolling than adding to the discussion. Especially from an anonymous newbie in his very first post to this forum.

--Ethan

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post #10398 of 10427 Old 07-18-2014, 11:00 AM
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Originally Posted by Ethan Winer View Post
The term bass trap has been used as far back as at least 1974, and probably even earlier, as you'll find in this back issue of dB magazine:

http://www.americanradiohistory.com/...DB-1974-09.pdf

Absorbing and trapping are basically the same thing. A mouse goes into a mouse trap and doesn't come out. Same for the Roach Motel. And again the same for bass entering a bass trap.

To call bass traps "nonsense" sounds more like trolling than adding to the discussion. Especially from an anonymous newbie in his very first post to this forum.

--Ethan

It's not really a "technical" term, it's more of a "marketing" term and there are a lot of people out there that confuse what it actually means.

Tthey aren't trapping they are ABSORBING. I know the industry has used that term, but that doesn't mean it's an accurate term.

Real Traps has Mondo Traps, does that mean they trap Mondos? Or MegaTraps trapping Megas? Or MicroTraps trapping Micros?

Serious Ethan, i think your argument is kind of, well, silly.

Why can't people call a low frequency absorption system a low frequency absorption system, just like they call Diffusors diffusors? Is there anything wrong with asking people to refer to acoustic treatment as to what it does rather than making up some term because it sounds good? Not all acoustic engineers refer to low frequency absorption systems as bass traps. Some dislike using the term.

The problem that's commonly occurring is that there are companies out there, without naming names because that's not important, refer to products as bass traps, but they are always absorbing low frequencies, they are absorbing midrange frequencies.
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Originally Posted by myfipie View Post
If you would like, you can read more about different kinds of Bass TRAPPING (ha ha) here.
http://www.gikacoustics.com/understa...bass-trapping/
Why are you trying to push your products on a web forum? Isn't that kind of cheesy way to market your products rather than discussing a topic of discussion? The topic of discussion is not referring to your products specifically, is it?
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post #10400 of 10427 Old 07-18-2014, 11:19 AM
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Why are you trying to push your products on a web forum? Isn't that kind of cheesy way to market your products rather than discussing a topic of discussion? The topic of discussion is not referring to your products specifically, is it?



It is talking about different kinds of TRAPPING vs you just coming on here to stir the pot. Ethan is 100% correct about the term BASS TRAP if it annoys you or not. Hate to see what real problems do to you if the term "bass traps" ANNOYS you so much. ha ha


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post #10401 of 10427 Old 07-18-2014, 11:23 AM
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Quote:
Originally Posted by Ethan Winer View Post
The term bass trap has been used as far back as at least 1974, and probably even earlier, as you'll find in this back issue of dB magazine:

http://www.americanradiohistory.com/...DB-1974-09.pdf

Absorbing and trapping are basically the same thing. A mouse goes into a mouse trap and doesn't come out. Same for the Roach Motel. And again the same for bass entering a bass trap.

To call bass traps "nonsense" sounds more like trolling than adding to the discussion. Especially from an anonymous newbie in his very first post to this forum.

--Ethan
Whatever Ethan.

Coming from someone that makes MegaTraps, MondoTraps and MicroTraps, that really says it all. There are no Mondos, Megas, or Micros in room acoustics.

:facepalm:
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post #10402 of 10427 Old 07-18-2014, 01:12 PM
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Whatever Ethan.
And WHATEVER, DrBlank. Get a life...
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post #10404 of 10427 Old 07-18-2014, 05:17 PM
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Question about FRK paper

This subject has been talked about a lot I know, but I have some questions. I am putting the OC 703 2" panels I have on my wall on my ceiling, and making thicker 3 inch panels to put in there place. They have about an inch of air gap. I've read that you should not use the FRK paper facing the room for reflection panels. I have also read that if you use the FRK paper on the ceiling facing the room it can help "give back" a little HF taken by the carpeting on the floor, sort of evening things out. How much extra LF absorption would I get if I put the FRK paper facing the ceiling and the wall on the side wall panels given that I have about an inch of air gap. Would it make that much of an improvement or is it a waste of time. I am also building a large 4 inch thick trap to put on my back wall between my surround speakers. Does it make sense to put FRK paper on this to help LF. My back row of seats is about 4 ft away from the wall and my front row is about 9 to 10 ft away.
Thanks
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post #10405 of 10427 Old 07-19-2014, 02:42 AM
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Speaking of using different materials in DIY diffusors. I can't afford those nice $1000 dollar rounded made of wood diffusors so I was thinking, can I use 'window coping' materials? There are some that are sort of rounded... on the outside they are cementitious but inside is just styrofoam... Good or Bad idea?


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post #10406 of 10427 Old 07-19-2014, 04:19 AM
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For people searching. You can get OC 703 (Owens Cornings 703) at Kamco Supply Corp in Woburn MA. It was $108 for 12 2x4 pieces as of 7/19/14.
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post #10407 of 10427 Old 07-19-2014, 03:29 PM
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Quote:
I have also read that if you use the FRK paper on the ceiling facing the room it can help "give back" a little HF taken by the carpeting on the floor, sort of evening things out.


If the panel are in the early reflection area on the ceiling then you do not want to use FRK.


Quote:
How much extra LF absorption would I get if I put the FRK paper facing the ceiling and the wall on the side wall panels given that I have about an inch of air gap. Would it make that much of an improvement or is it a waste of time.
I actually "re-treated" a studio a number of years ago that had 2" panels with the FRK on the back that was spaced off the wall. We replaced them with just normal two inch panels with a gap and that seemed to work much better. I think the FRK was not letting enough sound through the FRK to hit the wall, but instead reflecting back like it was a bare wall. Needless to say I would not recommend it.

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post #10408 of 10427 Old 07-19-2014, 03:29 PM
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I have also read that if you use the FRK paper on the ceiling facing the room it can help "give back" a little HF taken by the carpeting on the floor, sort of evening things out.


If the panel are in the early reflection area on the ceiling then you do not want to use FRK.


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How much extra LF absorption would I get if I put the FRK paper facing the ceiling and the wall on the side wall panels given that I have about an inch of air gap. Would it make that much of an improvement or is it a waste of time.


I actually "re-treated" a studio a number of years ago that had 2" panels with the FRK on the back that was spaced off the wall. We replaced them with just normal two inch panels with a gap and that seemed to work much better. I think the FRK was not letting enough sound through the FRK to hit the wall, but instead reflecting back like it was a bare wall. Needless to say I would not recommend it.
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post #10409 of 10427 Old 07-19-2014, 09:24 PM
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If the panel are in the early reflection area on the ceiling then you do not want to use FRK.






I actually "re-treated" a studio a number of years ago that had 2" panels with the FRK on the back that was spaced off the wall. We replaced them with just normal two inch panels with a gap and that seemed to work much better. I think the FRK was not letting enough sound through the FRK to hit the wall, but instead reflecting back like it was a bare wall. Needless to say I would not recommend it.
I was thinking of putting 9 2'x4' 2" thick Roxul R80 rockport sheets up for our ceiling... They will be first reflection points for the first and second row. Should I face them with paper since we have carpeted floors?

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post #10410 of 10427 Old 07-20-2014, 07:06 AM
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I was thinking of putting 9 2'x4' 2" thick Roxul R80 rockport sheets up for our ceiling... They will be first reflection points for the first and second row. Should I face them with paper since we have carpeted floors?

No, you never want to use facing on the panels if in the early reflection point.

http://www.gikacoustics.com/video-ea...ection-points/
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