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Absorbtion panels for early reflection
Old 28th April 2017
  #1
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ikamy's Avatar
 

Absorbtion panels for early reflection

Hello guys
First of all thanks to the people on this forum who help new comers to solve their problems

Just made couple of bass traps like these ones recently
They are 4 inches thick made of 2 layers of dense rockwool (D100)

Im installing them on the wall, they will cover all my CORNERS

Now its time to build absorbtion panels for my early reflection and center of the walls, behind my monitors and ceiling

Im wondering should I make the rest 2 inches or like bass traps 4 inches ?


Based on bob gold table Ive read on the mid and high frequency range
the 2inches and 4inches panels behave like each other
(Im not sure about low mid)

Please share your personal experience and the corret way

Im gonna use this room (4m x 3m x 2.85m height) for mixing and also recording vocals

Thanks
Attached Thumbnails
Absorbtion panels for early reflection-image_7420_0.jpg   Absorbtion panels for early reflection-image_1849_1.jpg   Absorbtion panels for early reflection-image_7268_0.jpg   Absorbtion panels for early reflection-image_2382_1.jpg  
Old 28th April 2017
  #2
Gear Maniac
Quote:
Originally Posted by ikamy View Post
Im wondering should I make the rest 2 inches or like bass traps 4 inches ?
All else being equal, 4" panels will be effective roughly one octave lower. You can browse commercial panel manufacturers' spec sheets to get an idea of the effective range (see f. ex Acoustic Panels | Bass Traps | Diffusors | GIK Acoustics and RealTraps - Product Test Data).
Old 28th April 2017
  #3
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ikamy's Avatar
 

Quote:
Originally Posted by Antti H View Post
All else being equal, 4" panels will be effective roughly one octave lower. You can browse commercial panel manufacturers' spec sheets to get an idea of the effective range (see f. ex Acoustic Panels | Bass Traps | Diffusors | GIK Acoustics and RealTraps - Product Test Data).
Im not sure about what you trying to say

I made my own panels, based on my limitation I couldn't build 6 inches panels for the corners my room is small,
So my panels probably are different from manufactured panels

So you mean I should build the rest 4 inches?

Based on this page
http://www.bobgolds.com/AbsorptionCoefficients.htm

On the Roxul rockwool section

There are not such a difference between 2", 5.9pcf (94kg /m3) and 4", 6pcf (96kg/m3) when it comes to mid / high frequency after 500hz I mean

I already made my bass traps, so the rest panels are going to place on the middle of the walls

I also noticed the lower density is more effective based on this table
Old 28th April 2017
  #4
Gear Guru
Reflections

Looking good. The side walls and ceiling will reflect bass unless they are very very lightly built.
Many of us here suggest a minimum of 4" PLUS a 4" airgap.
IMO it's pretty much a waste of energy and money to build thinner.
DD
Old 28th April 2017
  #5
Gear Maniac
Quote:
Originally Posted by ikamy View Post
Im not sure about what you trying to say
I'm saying that 4" panels will remove that particular reflection one octave lower than 2" panels. Bass traps are different and are about damping room modes (relatively sharp resonant peaks). Thick absorber panels will be more effective at removing non-resonant (direct reflection) peaks and notches. There's probably also a caveat that the panel will be less effective when the width / height is small relative to wavelength.

Whether you consider the possible benefit of thicker panels to be worth the effort is up to you.
Old 28th April 2017
  #6
Gear Guru
 
Glenn Kuras's Avatar
[QUOTE]Im wondering should I make the rest 2 inches or like bass traps 4 inches ?/QUOTE]

If budget is not a problem them make them 4". 2" can work, but only for rooms with lower budget or no room to fit 4".
Old 28th April 2017
  #7
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JWL.GIK's Avatar
Agreed with above. If you have a good bass trapping strategy in place and limited budget or space at reflection points, you can get away with 2" panels. Thicker is better.
Old 28th April 2017
  #8
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ikamy's Avatar
 

Thank you very much
No problem with budget,

One thing which made me worry was the Bob Gold table

"Based on that lower density absorb more mid/high than higher density"

What do you suggest about density?

For bass trapping, I used 2 layer of 2" rockwool each 100kg /m3 (about 6pcf)

What density is suitable for the rest which Im gonna install on the early reflection points, middle, ceiling ?
Old 29th April 2017
  #10
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ikamy's Avatar
 

Thank you
Ive read those links
Also checked the calculator

Im confused
I cant even put a right data to the calculator

My material is a normal Rockwool, not very famous industry standard material like 703 or ...

I also dont know anything about flow resistancy! No information on the box

Just density (which in the case of Broadband bass trap I used 2 layer of 2" (100kg/m3) each

But you mentioned lighter material is better for early reflection

And somewhere else you mentioned if you want to target low mid maybe you want to use higher density

Im going to build 4" panel with 4" air gap
But still dont know which density is suitable for early reflection points, the front wall , the ceiling and the backwall
Old 29th April 2017
  #11
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Jens Eklund's Avatar
 

Density is not what matters most. GFR (Gas Flow Resistivity) is. Search the forum and you'll find plenty of info.
Old 29th April 2017
  #12
Registered User
 

Quote:
Originally Posted by Jens Eklund View Post
Density is not what matters most. GFR (Gas Flow Resistivity) is. Search the forum and you'll find plenty of info.
Any GFR data of 20kg/m3 polyester wool panels you know of?
Did a search but couldn't find any.

Thanks.
Old 29th April 2017
  #13
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Jens Eklund's Avatar
 

I only use Rockwool (the actual brand). There's a few threads in this forum that lists GFR for different products.
Old 29th April 2017
  #14
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ikamy's Avatar
 

Quote:
Originally Posted by Jens Eklund View Post
Density is not what matters most. GFR (Gas Flow Resistivity) is. Search the forum and you'll find plenty of info.
Sir, a few moments ago I called the company produced Rockwool

They dont know what Gas / Air Flow Resistivity is

In my country its rare you find a supplier with high technical information
Besides, I really dont have access to order from somewhere else or other company

Thats all I can buy with different density

In this photo its 100kg / m3
Its pretty dense

If you think its suitable I use the same for the rest
Attached Thumbnails
Absorbtion panels for early reflection-image.jpg  
Old 29th April 2017
  #15
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Jens Eklund's Avatar
 

100kg/m3 normally results in a too high GFR value. Assuming Rockwool (and again, just to be clear: the actual brand Rockwool, not just any mineral wool); you normally want to stay within about 25-40 kg/m3 assuming not very thin panels.

The type I normally use is 30 kg/m3 and is good for panels ranging between about 200-400 mm.
Old 29th April 2017
  #16
Gear Addict
 
ikamy's Avatar
 

Quote:
Originally Posted by Jens Eklund View Post
100kg/m3 normally results in a too high GFR value. Assuming Rockwool (and again, just to be clear: the actual brand Rockwool, not just any mineral wool); you normally want to stay within about 25-40 kg/m3 assuming not very thin panels.

The type I normally use is 30 kg/m3 and is good for panels ranging between about 200-400 mm.
And this density will take care of Bass reflection from the side walls also?

I doubt I can find anything below 50kg / m3
Old 29th April 2017
  #17
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Jens Eklund's Avatar
 

How well a panel will behave is directly related to size compared to wavelength of the frequency of interest.
Old 29th April 2017
  #18
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ikamy's Avatar
 

Also I already made alot of bass traps for the corners like 12 panels 4" with high density , so you say they were a waste :( :(
Old 29th April 2017
  #19
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Jens Eklund's Avatar
 

Quote:
Originally Posted by ikamy View Post
Also I already made alot of bass traps for the corners like 14 panels 4" with high density , so you say they were a waste :( :(
Not necessarily, but the performance will be hard to predict since they will behave as a kind of damped membrane. Deep traps with appropriate wool (GFR) depending on depth is a safer bet, but even better (in my opinion) is a slotted panel since you can reach good performance with less depth and also reduce the risk of overdamping a room in the higher frequency range (as so often happens if using only porous absorption).
Old 29th April 2017
  #20
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ikamy's Avatar
 

Thank you for your time
I should stick to the foam from the beginning ...
Old 29th April 2017
  #21
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Jens Eklund's Avatar
 

Quote:
Originally Posted by ikamy View Post
I should stick to the foam from the beginning ...
Old 29th April 2017
  #22
Gear Guru
 
Glenn Kuras's Avatar
Quote:
Originally Posted by ikamy View Post
Thank you for your time
I should stick to the foam from the beginning ...
If that is the case then you could have used 1" fiberglass.
Old 29th April 2017
  #23
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ikamy's Avatar
 

Guys This is my first experience
So I probably messed up

With only 6 panels of total 12 panels in my room, I feel its damped
I dont know After installing all them exactly on the corners, the dampness increase or not

And probably with more 4 inches panels (low density 50kg/m3) on the side walls, front walls and ceiling it will become a dead room !

My room dimension is 4m x 3m = 12 square meter

And I dont know this much dampness will improve my mixes or not

I have both Vertical bass traps and Horizontal (for up corners)
Maybe I should reduce the horizontal ones ??
Attached Thumbnails
Absorbtion panels for early reflection-image.jpeg  
Old 29th April 2017
  #24
Gear Guru
Dead

Lack of reflections during the first 20mS or so is really beneficial. The clarity increase is so vivid it will probably prompt you to turn your tweeters down. All good.
Here's is a large source of example GFR's. Common Gas Flow Resistivity numbers.
Note the PAC is just a calculator which omits the damped membrane behaviour of semi rigid panels. And corner placement. An old Ethan Winer actual test favoured 100KG which has a side benefit of not sagging.
Many commercial traps use 100KG, I believe GIK find 60 works better for them. Having said that, many many people are finding a big void in their LF response due to mid width mid height listener position coupled with inadequate i.e. thin, side and overhead treatment. If the space is available and the spirit willing..... a deep low GFR treatment is much more powerful than 100mm ones.

DD

Last edited by DanDan; 29th April 2017 at 03:30 PM..
Old 29th April 2017
  #25
Gear Addict
 
ikamy's Avatar
 

Ive read enough to make me convinced I did it wrong, probably making 12 panels with high density was a silly idea
But the fact is I posted my idea with numbers, pics, etc couple of times in couple of threads in this forum , no one mentioned Im calculating density wrong so I thought Im doing right
It happens, its a trial and error
Ive come to this conclusion that Im not lucky on getting advice on the forums, same thing happend when I got my studio monitors, I had better options. But I think we all did these mistake during our career.
So Im going to use fiberglass 4" panels density lower than 30kg/m3 with 4" air gap for the rest of them room (early reflection, front wall, ceiling)

Thanks to everyone
Old 30th April 2017
  #26
Gear Guru
Data

I recommend you look at Absorption data for the various densities and thickness st bobgolds. com DD
Old 30th April 2017
  #27
Gear Addict
 
ikamy's Avatar
 

Quote:
Originally Posted by DanDan View Post
I recommend you look at Absorption data for the various densities and thickness st bobgolds. com DD
Yes sir, that was the very first reason I made my bass traps 4" and dense (100kg /m3)

And I dont see any problem based on the BOB GOLD DATA

But your claim about the air flow resistivity is exactly opposite from what Ive read on that table

http://www.bobgolds.com/AbsorptionCoefficients.htm
Here
The table said between 4" too dense (94kg/m3) like mine and less dense (40kg/m3) there are differences but too little

On the Roxul Rockwool section 4" if you notice
For example for the 2000Hz dense material NRC is 1.06 and light material NRC is 1.08

Yes the overal NRC of light material is higher but its a 0.05 difference !

The interesting point is light material Absorb 125HZ below NRC 1 (0.86) but dense material NRC is 1

The only range is lighter material absorb significantly higher is 250HZ and 500HZ
Which lighter material numbers are 1.11 and 1.20
And deser material numbers are 0.95 and 1.06

But even with that fact the denser material absorb all frequency range at the equal rate
Not like lighter material which abosrb 125 HZ or 4000Hz significantly lower than 500Hz

Ive read all these information before I started and Im pretty noob

If Im arguing, thats because Im curious to learn and want to make rest of the panels in the right way

Thank you
Old 30th April 2017
  #28
Gear Addict
 
ikamy's Avatar
 

And one thing Im not sure these data relate to my case becuase I didnt build superchunk traps , they are just panels and yes their placement degree causes air gap behind them

And Bob gold data didnt mention about the air gap or anything
Old 1st May 2017
  #30
Gear Nut
Hello Ikamy,

I was in a similar position to you when treating my studio. So many choices, but ultimately you have to go with something or you'd never build anything. Rest assured that while your work may or may not be the 100% best solution, it's going to be much, much better than nothing, and certainly won't be a waste of time.

I went for a similar approach too, using Rockwool RW5 4" (100mm) slabs for the bass traps. I believe it has a density of 100kg/m3. I bought this because various sources indicated it worked well. Also, manufacturer specs indicated superior low frequency absorption than the less dense equivalent. I also used 2" thick panels for the side and ceiling 1st reflections. Most of these were bought, not DIY. They work really well, impulse response at the listening position is superb. I've attached a photo of the room.

Anyway, the proof of the pudding is in the eating. The room sounds fantastic, mixes translate very well indeed, and recordings sound great. You mentioned that your room will be used for mixing and recording vocals so it's perfectly possible this approach will work for yours too.

If you are not doing so already, I'd recommend using room measurement software like REW to reassure yourself that you are improving matters over the empty room, and guide you to good placement of the speakers and treatment etc.

Jennifer
Attached Thumbnails
Absorbtion panels for early reflection-crw_0006.jpg  

Last edited by endorka; 1st May 2017 at 09:52 AM..
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