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3" Roxul enough for early/first reflections?
Old 17th October 2014
  #1
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heisleyamor's Avatar
 
🎧 15 years
3" Roxul enough for early/first reflections?

I have superchunks in all corners and have a 6" thick cloud above my mixing area. I also have a large bass trap in the back of my room (filled a closet with roxul safe'n'sound). Is 3" enough for early reflections or would 6 be noticeably better? I'm nervous about taking up too much room since it is not very wide (about 12 feet wide by 22 feet long). But that might be an even bigger reason to go thicker. Any suggestions?
Old 17th October 2014
  #2
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sheggs's Avatar
 
🎧 10 years
Yes, 3' inch should be thick enough for your first reflection points. You are looking at the high and mids here primarily. A lot of people do like thicker panels for the cloud though
Old 17th October 2014
  #3
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Jens Eklund's Avatar
 
🎧 10 years
HereΒ΄s my opinion:


Make the panels as deep as possible, at least about 6” but preferably 12” or deeper. A 3” panel will only be effective down to about 300-400 Hz and this will only EQ the reflection leaving the lower frequency range unattended, and this will mess up the lower part of the response due to SBIR.

I always try to make the first order reflection panels at least about 8” but often 14-20” if possible. Needless to say, you need to select an appropriate wool (with suitable flow resistivity) deepening on the thickness used for optimal performance. Multi-layer Absorber Calculator

In small room acoustics, we are primarily concerned with lower order reflections and these will always be at specific angles of incident, so relying on absorption coefficients sourced from random incident measurements (reverberation chambers) might be hazardous. First order reflections usually occur at between 0 to about 30 degrees incident angel to the boundary. Ideally, you want a panel that absorbs all the way down to the cutoff of the speaker, but if the monitor is positioned close to the boundary, you might get away with a thinner panel (not effective at low frequencies) since the difference in travel distance between the direct sound and the reflection from this boundary will be small and a constructive phase relation between direct and reflected sound will occur fairly high up in the frequency range, and assuming you can compensate of this low frequency boost by adjusting your monitor, this might not be a big problem.

Also, one needs to consider the directivity of a normal monitor. The energy hitting the reflection points at the sides, ceiling and behind the speaker is mostly made up of low frequency energy since the monitor is close to omnidirectional at low frequencies but becomes more directional at higher frequencies, so there might not be a strong need to absorb the highest range at these points relative to the lower frequency range depending on where they are located in relation to the source and the directional properties of it.
Old 17th October 2014
  #4
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heisleyamor's Avatar
 
🎧 15 years
I've seen similar questions previously, but can't seem to find a whole lot right now... But would 3" with 3" gap (or 3" with 1" gap) be better than 6" with no gap? I'm worried about putting a 6" wide piece of wood right against the walls for early reflections and creating new corners where bass can build up.
Old 17th October 2014
  #5
Gear Guru
 
1 Review written
🎧 15 years
DEEP

+1, I concur entirely with Jens. Small addition, we typically sit at half width, a modal hot spot, which is often reinforced by the vertical. We need deep side traps or VPR's as much as we do Clouds or Back Wall treatment.
It is common to see a MINIMUM recommendation for any traps to be 100 MM plus 100 MM air gap, almost as good as say 180MM of fibre. Fibre That's a MINIMUM. To be honest I see little point to thinner traps. Waste of frame fabric and time.
Quote:
But would 3" with 3" gap (or 3" with 1" gap) be better than 6" with no gap?
No, fibre is better than air.

DD
Old 17th October 2014
  #6
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Glenn Kuras's Avatar
 
🎧 15 years
The bottom line is if you can go thicker and have the space then yes go for it. But if you can't go that thick then 3" is 10000% better then a bare wall.
Old 17th October 2014 | Show parent
  #7
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by heisleyamor ➑️
... would 3" with 3" gap (or 3" with 1" gap) be better than 6" with no gap?
No, especially not 3" +1". Did you notice the link in my post?

Quote:
Originally Posted by heisleyamor ➑️
I'm worried about putting a 6" wide piece of wood right against the walls for early reflections and creating new corners where bass can build up.
Assuming you mean "wool" and not "wood"; do not worry about that.
Old 17th October 2014
  #8
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avare's Avatar
 
🎧 15 years
3" is not sufficient. 4" is the minimum recommended by many designers and 8" minimum preferred.

Andre
Old 17th October 2014
  #9
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1 Review written
🎧 15 years
Wood

I think he did mean wood Jens. But either way no real problem. I am sure you will agree that the six inch deep framing wood is nothing compared to the big lump of fibre. Bass will not see such a frame as a corner with consequent build up.

DD
Old 17th October 2014
  #10
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heisleyamor's Avatar
 
🎧 15 years
Thanks for the info everyone. I am going to do 6" on all early reflections with no gap. I may need a small gap on my angled wall traps because I am not sure how to keep it flush to the walls - will most likely have to use hooks. I have strange angled walls and I have a 10db mode around 145hz and think the main angled wall has a lot to do with that because when I stand over there that frequency gets louder. So the only thing left will be the front wall-ceiling corner. Guess I will do 6" there, but hopefully the front window doesn't get in the way.

Pic is pre-treatment and other changes:
Old 17th October 2014 | Show parent
  #11
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by DanDan ➑️
I think he did mean wood Jens. But either way no real problem. I am sure you will agree that the six inch deep framing wood is nothing compared to the big lump of fibre. Bass will not see such a frame as a corner with consequent build up.

DD
Yes, one would need a lot of mass and surface area to make a β€œcorner” that would act as an obstacle at low frequencies.
Old 17th October 2014 | Show parent
  #12
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by heisleyamor ➑️
Thanks for the info everyone. I am going to do 6" on all early reflections with no gap. I may need a small gap on my angled wall traps because I am not sure how to keep it flush to the walls - will most likely have to use hooks. I have strange angled walls and I have a 10db mode around 145hz and think the main angled wall has a lot to do with that because when I stand over there that frequency gets louder. So the only thing left will be the front wall-ceiling corner. Guess I will do 6" there, but hopefully the front window doesn't get in the way.

Pic is pre-treatment and other changes:
Are you sure that 145 Hz is not the 0,0,2 mode (second mode related to height)?
Old 18th October 2014 | Show parent
  #13
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Jolida's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➑️
Are you sure that 145 Hz is not the 0,0,2 mode (second mode related to height)?
If it is the 0,0,2 mode as u say, will he benefit with say an 8 inch thick cloud to target that? Then what are waveguides used for, if the panel itself is absorbant?
Old 18th October 2014 | Show parent
  #14
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jolida ➑️
If it is the 0,0,2 mode as u say, will he benefit with say an 8 inch thick cloud to target that? Then what are waveguides used for, if the panel itself is absorbant?
I did not say that it is the 0,0,2 mode, I say it might be, and yes; assuming large enough (and assuming in the right place), an 8" panel would do some damage to that mode but thicker would be even better (or pressure based absorber if not an early reflection point).

"Waveguides"?
Old 18th October 2014 | Show parent
  #15
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Jolida's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➑️
I did not say that it is the 0,0,2 mode, I say it might be, and yes; assuming large enough (and assuming in the right place), an 8" panel would do some damage to that mode but thicker would be even better (or pressure based absorber if not an early reflection point).

"Waveguides"?
Yes if that's what it's called..


https://gearspace.com/board/8916436-post28.html
https://gearspace.com/board/8916607-post29.html
Old 18th October 2014 | Show parent
  #16
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heisleyamor's Avatar
 
🎧 15 years
Quote:
Originally Posted by Jens Eklund ➑️
Are you sure that 145 Hz is not the 0,0,2 mode (second mode related to height)?
I'm not positive without taking measurements. I hope the 6" cloud is enough. I already had to create a 5" gap due to a light. So it is hanging down about one foot with an 8 foot ceiling. I plan on putting the cloud up this weekend. Hopefully that will remove the 145-155hz mode.
Old 18th October 2014 | Show parent
  #17
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Jens Eklund's Avatar
 
🎧 10 years
Quote:
I would personally restrict the term "waveguide" to include what is used to increase the sensitivity and control the directivity of a speaker driver. What you refer to, I would simply label; geometry to redirect early reflected energy away from the sweet spot in order to avoid HF absorption when establishing a suitable ISD-gap.
Old 18th October 2014 | Show parent
  #18
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Jolida's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jens Eklund ➑️
I would personally restrict the term "waveguide" to include what is used to increase the sensitivity and control the directivity of a speaker driver. What you refer to, I would simply label; geometry to redirect early reflected energy away from the sweet spot in order to avoid HF absorption when establishing a suitable ISD-gap.
Cool
Old 19th October 2014
  #19
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heisleyamor's Avatar
 
🎧 15 years
Here is the cloud in case you were wondering. I hung it up today. You were right about the 145hz. The cloud completely brought it down about 12-15db and got rid of almost all of the ringing I had in the room.

Old 19th October 2014
  #20
Gear Guru
 
1 Review written
🎧 15 years
Cool

Nice one.
DD
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