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BASS TRAPS..Achilles' heel!!
Old 30th January 2013
  #1
Here for the gear
 
🎧 5 years
BASS TRAPS..Achilles' heel!!

Hi there! I'm pretty new so first of all i wanna thank you for aaaaallllll your help!
I've read all the "building studios" threads but some doubts are still in my mind, so that is the question:

I've to build 4 bass traps (broad traps, not helmotz). I want to know WICH IS BETTER IN TERMS OF FREQUENCY TREATMENT? AND WHY?

- SUPER CHUNK CORNER BASS with all the corner triangle full of rockwool 40 kg/m3. For all the 4 corners

- 1 PANEL 300cmx60cmx10cm AT EVERY CORNER WITH EMPY SPACE BEHIND (floor ceiling, my room is 3m height) formed by 6 120x60x5 rockwool panel 70 kg/m3. thickness will be 10 cm.

Please help me to understand the real differences, pros/contros.
Old 30th January 2013
  #2
Gear Guru
 
Ethan Winer's Avatar
 
🎧 15 years
Lightbulb

Filling a corner solid is best, but it uses much more material. The quote below from my Audio Expert book explains the trade-off. Note that making either type of corner trap wider also helps to absorb more and to a lower frequency.

--Ethan

The Acoustic Treatment Experts

Quote:
Originally Posted by The Audio Expert
Filling a corner fully with rigid fiberglass is only a little better than using a four-inch-thick panel straddling the corner. If you can afford only a limited amount of material, it’s better to have more panels straddling additional corners, rather than fewer corners filled solid. Since the material in the deepest part of a corner is near to the wall boundaries, there’s less wave velocity for the material to act on. But when performance matters more than cost, filling a corner fully does maximize absorption. A good compromise is to place rigid fiberglass panels four inches thick straddling each corner, with the cavity behind each panel filled with less expensive fluffy fiberglass.
Old 30th January 2013
  #3
Here for the gear
 
🎧 5 years
Thanks Ethan your book and site were and are the real guru for me!
So super chunk are better!
My room is 4mx4mx3m..so do you think it would be better to build super chunk with 70 kg/m3 rockwool?
40 kg/m3 is not enough and it would be a waste of money?
Simple 300cm x60cm x 10 cm panel would be a waste of money too?
I could build a superchunk with 40kg/m3 rockwool..than put in front of that 3 panel (120cmx60cmx5cm) of 70kg/m3 rockwool (like a tower floor to ceiling 5cm thick)..could it be a good compromise?
Old 31st January 2013 | Show parent
  #4
Gear Guru
 
Ethan Winer's Avatar
 
🎧 15 years
Lightbulb

Only you can decide how much extra cost is "worth it" to make a chunk versus panel.

--Ethan
Old 1st February 2013
  #5
Gear Guru
 
Glenn Kuras's Avatar
 
🎧 15 years
Considering that room treatment will have the largest impact and by far cost way less then all the other gear, I think it is a no brainier to make the panels as large as possible and cover enough to tame the room.
Old 9th April 2016
  #6
Lives for gear
 
andre tchmil's Avatar
 
🎧 15 years
Quote:
Originally Posted by Thomas Elder ➡️
Hi there! I'm pretty new so first of all i wanna thank you for aaaaallllll your help!
I've read all the "building studios" threads but some doubts are still in my mind, so that is the question:

I've to build 4 bass traps (broad traps, not helmotz). I want to know WICH IS BETTER IN TERMS OF FREQUENCY TREATMENT? AND WHY?

- SUPER CHUNK CORNER BASS with all the corner triangle full of rockwool 40 kg/m3. For all the 4 corners

- 1 PANEL 300cmx60cmx10cm AT EVERY CORNER WITH EMPY SPACE BEHIND (floor ceiling, my room is 3m height) formed by 6 120x60x5 rockwool panel 70 kg/m3. thickness will be 10 cm.

Please help me to understand the real differences, pros/contros.


Is the 70kg/m3 not too stiff for it's purpose ?
Old 10th April 2016 | Show parent
  #7
Gear Nut
 
🎧 5 years
Quote:
Originally Posted by Ethan Winer ➡️
Filling a corner solid is best, but it uses much more material. The quote below from my Audio Expert book explains the trade-off. Note that making either type of corner trap wider also helps to absorb more and to a lower frequency.

--Ethan

The Acoustic Treatment Experts
Would you recommend putting a membrane on all corner traps, or not bothering?

I have some kraft paper to do this.
Old 11th April 2016 | Show parent
  #8
JWL
Lives for gear
 
JWL's Avatar
 
🎧 10 years
Quote:
Originally Posted by keenly ➡️
Would you recommend putting a membrane on all corner traps, or not bothering?

I have some kraft paper to do this.
Yes, if you can do the membrane properly it will greatly improve the performance of corner traps. I would do it if you can.
Old 13th April 2016 | Show parent
  #9
Gear Nut
 
🎧 5 years
Quote:
Originally Posted by JWL ➡️
Yes, if you can do the membrane properly it will greatly improve the performance of corner traps. I would do it if you can.
I have applied adhesive to kraft paper then put on top on absorption. It is not easy using the lightweight roll types, impossible to make sure every cm of paper is glued into position. I will just have to do it the best I can.

Is there a better way?
Old 14th April 2016
  #10
JWL
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JWL's Avatar
 
🎧 10 years
Kraft paper can work OK if it is properly bonded to the absorbent.

But yes, there are better methods & materials. We put a ton of R&D into this when designing our bass traps, to really dial it in. It's not easy to replicate what we do in a DIY shop, so things like Kraft paper are often the best choice for a DIY product.
Old 14th April 2016 | Show parent
  #11
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sheggs's Avatar
 
🎧 10 years
Quote:
Originally Posted by JWL ➡️
Yes, if you can do the membrane properly it will greatly improve the performance of corner traps. I would do it if you can.
With all membranes though whatever you use they may increase the low end performance but they will also have an effect on the mids and higs in a reflective way. Without using a professional test what this effect is going to be (unless you can find some figures on them) is not easily quantifiable. However it is going to reflect some frequencies. So when using membrane traps it does depend on what else is in the room and other room acoustic variables.
Old 14th April 2016 | Show parent
  #12
Gear Nut
 
🎧 5 years
Quote:
Originally Posted by JWL ➡️
Kraft paper can work OK if it is properly bonded to the absorbent.

But yes, there are better methods & materials. We put a ton of R&D into this when designing our bass traps, to really dial it in. It's not easy to replicate what we do in a DIY shop, so things like Kraft paper are often the best choice for a DIY product.
What about the plastic that insulation rolls come in?
Old 15th April 2016 | Show parent
  #13
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sheggs's Avatar
 
🎧 10 years
Quote:
Originally Posted by keenly ➡️
What about the plastic that insulation rolls come in?
Yep, you can leave them in the plastic. The only issues to be aware of then is -

a) That is is all tightly wrapped and ideally it needs to be opened up to be most effective
b) Without actually trying it, I could not say what frequencies would be reflected back and at what absorption coefficient
Old 18th April 2016
  #14
Here for the gear
 
🎧 5 years
6ft Corner Traps were easy....

I built four 6ft bass traps using a wooden frame design and Roxul Safe n Sound I found at Lowe's for about $45 per bag. One 6ft trap uses exactly 4 batts of insulation. I use the 3" thick kind of 16" on-center (means 15" width). Works fabulous!
Only 3 are pictured, but I built four of them. Total cost was about $55 each. Not too bad and it only took me one full day for all 4.
Attached Thumbnails
BASS TRAPS..Achilles' heel!!-basstrap1.jpg   BASS TRAPS..Achilles' heel!!-basstrap2.jpg   BASS TRAPS..Achilles' heel!!-basstrap3.jpg  
Old 21st April 2016 | Show parent
  #15
Gear Maniac
 
🎧 5 years
Quote:
Originally Posted by andre tchmil ➡️
Is the 70kg/m3 not too stiff for it's purpose ?
Yes, it's too dense. I tried panel bass traps with these, and they don't work as well as Safe'n Sound at 40 kg/m3. The theory agrees too with this. Too dense will reflect low frequency more than absorb it.
Old 22nd April 2016 | Show parent
  #16
Lives for gear
 
🎧 5 years
Quote:
Originally Posted by Sailboarder ➡️
Yes, it's too dense. I tried panel bass traps with these, and they don't work as well as Safe'n Sound at 40 kg/m3. The theory agrees too with this. Too dense will reflect low frequency more than absorb it.
Hello,


The most important parameter is the air or gas flow resistivity.

Knauf TI312 11.8 kg/m3 and a GRF of 11.7
Knauf classic 035 20,1 kgm3 and a grf of 5.7

The most important is to use a wool or a fiber with the lowest GFR.

The second parameter is the impedance, hight impedance is better but to find someone to explain this impedance is an impossble mission.
Old 24th April 2016 | Show parent
  #17
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JulianFernandez's Avatar
 
🎧 10 years
Quote:
Originally Posted by FatNinjuh ➡️
I built four 6ft bass traps using a wooden frame design and Roxul Safe n Sound I found at Lowe's for about $45 per bag. One 6ft trap uses exactly 4 batts of insulation. I use the 3" thick kind of 16" on-center (means 15" width). Works fabulous!
Only 3 are pictured, but I built four of them. Total cost was about $55 each. Not too bad and it only took me one full day for all 4.
Look great, man!
Old 28th April 2016
  #18
Here for the gear
 
🎧 5 years
Very nice! What kind of fabric did you cover them with?
Old 28th April 2016
  #19
Lives for gear
 
🎧 5 years
There are the burlap colored for little budgets.

https://www.onlinefabricstore.net/pr...t=color-burlap
Old 1st May 2016 | Show parent
  #20
Lives for gear
 
andre tchmil's Avatar
 
🎧 15 years
Quote:
Originally Posted by dinococcus ➡️
Hello,


The most important parameter is the air or gas flow resistivity.

Knauf TI312 11.8 kg/m3 and a GRF of 11.7
Knauf classic 035 20,1 kgm3 and a grf of 5.7

The most important is to use a wool or a fiber with the lowest GFR.

The second parameter is the impedance, hight impedance is better but to find someone to explain this impedance is an impossble mission.

Well I already mounted some 70 kg / m3 on my ceiling and my measurement results already improved significant.

I have more room where the 4" of 70kg already is, an can easily remove it again.
My question is : I want to mount another 4", this time 45kg/m3, In what layer order should I stack it, the dense closest to the ceiling, or vice versa, or in an alternate order ?
Old 1st May 2016
  #21
Gear Maniac
 
🎧 5 years
At low frequencies, the dense reflects too much. To lower this effect, the sound should go through the 45 first, and then in the 70. Having a less dense material in front of the denser adapts the impedances reducing the reflections.
Old 2nd May 2016 | Show parent
  #22
Lives for gear
 
🎧 5 years
Quote:
Originally Posted by andre tchmil ➡️
Well I already mounted some 70 kg / m3 on my ceiling and my measurement results already improved significant.

I have more room where the 4" of 70kg already is, an can easily remove it again.
My question is : I want to mount another 4", this time 45kg/m3, In what layer order should I stack it, the dense closest to the ceiling, or vice versa, or in an alternate order ?

Acoustic Modelling - Home Page for the simulation.
Old 14th August 2016 | Show parent
  #23
Here for the gear
 
Quote:
Originally Posted by dinococcus ➡️
Hello,


The most important parameter is the air or gas flow resistivity.

Knauf TI312 11.8 kg/m3 and a GRF of 11.7
Knauf classic 035 20,1 kgm3 and a grf of 5.7

The most important is to use a wool or a fiber with the lowest GFR.



The second parameter is the impedance, hight impedance is better but to find someone to explain this impedance is an impossble mission.
So, which Knauf is good for super chunk bass traps?
Old 15th August 2016 | Show parent
  #24
Lives for gear
 
🎧 15 years
Quote:
Originally Posted by ChriA ➡️
So, which Knauf is good for super chunk bass traps?
Ummm...

Acoustic Modelling - Home Page
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