Should I fret about cotton batting vs rockwool? And which rockwool R rating is recommended even?
The thickness factor comes from the filling of the cavity from about halfway to the back of the slot. About 10" thick. According to HornResp, with enough density of damping efficacy... doing so will not touch LF very much if at all but the HF will look almost as if no slot was involved.
The thickness factor comes from the filling of the cavity from about halfway to the back of the slot. About 10" thick. According to HornResp, with enough density of damping efficacy... doing so will not touch LF very much if at all but the HF will look almost as if no slot was involved.
According an AI generated generalization
- Low-density rockwool: Airflow resistivity ranging from 500 to 2,000 MKS rayls/m.
- Medium-density rockwool: Airflow resistivity ranging from 2,000 to 6,000 MKS rayls/m.
- High-density rockwool: Airflow resistivity ranging from 6,000 to 12,000 MKS rayls/m.
ComfortBatt
Safe and sound
Roxul
Comfortboard 80
More AI comments;
"Sure, here are some common materials found in acoustic applications along with their typical sound absorption coefficients (NRC values) across a range of frequencies:
"
Here are the typical sound absorption coefficients (NRC values) for cotton, polyester, wool batting, and foam materials commonly used in acoustic applications:
| Density | (>32 kg/m³ |
|---|
Safe and sound
| Density | (38 kg/m³) |
|---|
Roxul
| Density | (64 kg/m³) |
|---|
Comfortboard 80
| Density | (128 kg/m³) |
|---|
More AI comments;
"Sure, here are some common materials found in acoustic applications along with their typical sound absorption coefficients (NRC values) across a range of frequencies:
- Fiberglass: NRC 0.70 to 1.00
- Mineral Wool: NRC 0.80 to 1.00
- Rockwool: NRC 0.80 to 1.00
- Foam Panels (Open-Cell): NRC 0.40 to 0.70
- Foam Panels (Closed-Cell): NRC 0.05 to 0.35
- Fabric Panels: NRC 0.30 to 0.90
- Perforated Wood Panels: NRC 0.20 to 0.60
- Acoustic Ceiling Tiles: NRC 0.60 to 0.80
- Carpeting: NRC 0.10 to 0.50
- Glass Wool: NRC 0.25 to 0.60
"
Here are the typical sound absorption coefficients (NRC values) for cotton, polyester, wool batting, and foam materials commonly used in acoustic applications:
- Cotton batting: NRC 0.20 to 0.50
- Polyester batting: NRC 0.15 to 0.40
- Wool batting: NRC 0.10 to 0.40
- Foam panels (Open-Cell): NRC 0.40 to 0.70
- Foam panels (Closed-Cell): NRC 0.05 to 0.35
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Rockwool is clearly the more refined product with a range of densities, but in the end it will work about the same as cotton batting. It's just a matter of getting the right amount. Placed in the high velocity region of the port the effectiveness will be large.
According to AI;
Wool Batting:
- MKS rayls/m: The range can vary depending on the specific product, but typically falls within 1,000-2,500 MKS rayls/m.
- MKS rayls/m: The range can vary depending on the specific product, but typically falls within 1,000-2,500 MKS rayls/m.
- MKS rayls/m: The range can vary depending on the specific product, but typically falls within 1,000-2,000 MKS rayls/m.
Or
Wool Batting:
- Low density: 10-30 kg/m³, MKS rayls/m: 1,000-1,500 MKS rayls/m
- Medium density: 30-50 kg/m³, MKS rayls/m: 1,500-3,000 MKS rayls/m
- High density: 50-100 kg/m³, MKS rayls/m: 3,000-5,000 MKS rayls/m
- Low density: 10-30 kg/m³, MKS rayls/m: 1,000-1,500 MKS rayls/m
- Medium density: 30-50 kg/m³, MKS rayls/m: 1,500-2,500 MKS rayls/m
- High density: 50-100 kg/m³, MKS rayls/m: 2,500-3,000 MKS rayls/m
- Low density: 10-30 kg/m³, MKS rayls/m: 1,000-1,500 MKS rayls/m
- Medium density: 30-50 kg/m³, MKS rayls/m: 1,500-2,000 MKS rayls/m
- High density: 50-100 kg/m³, MKS rayls/m: 2,000-3,000 MKS rayls/m
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Above, Red is 25% filled and Grey is 50% filled.
Below, Red is Fr1 1000 and Grey is 12,000
Below, Red is Fr1 3000 and Grey is 12,000
Another element is internal damping, I have not used any in the PPSL as of yet. Time to fill her up.
Do you have any measurements? Put the wool you have in the slot and compare the changes with the model..
Bit the bullet and went with this, should be enough to do 2 slots and 2 innards... . The cotton batting can be used as the outer shell.
25-50% of the slot filled looks like passable performance.
AFB
Safe and sound
Not yet, I need to build the damping blocks, insert them, and then measure. I mean theres nothing to do but build it and apply it, seems like if I go for 50% fill, the rest will come out in the wash. I have to build 3 vertical columns to fit between the threaded rod connecting the woofers, in order to reach 50%, but it should be pretty easy once I get going.
25-50% of the slot filled looks like passable performance.
AFB
| Density | (> 40 kg/m3 ) |
|---|
Safe and sound
| Density | (38 kg/m³) |
|---|
Not yet, I need to build the damping blocks, insert them, and then measure. I mean theres nothing to do but build it and apply it, seems like if I go for 50% fill, the rest will come out in the wash. I have to build 3 vertical columns to fit between the threaded rod connecting the woofers, in order to reach 50%, but it should be pretty easy once I get going.
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Some may be tempted to use cotton or foam as room treatment or cabinet treatment.
Consider your exits carefully. Fiberglass wins as long as you keep it out of your lungs.
https://en.wikipedia.org/wiki/The_Station_nightclub_fire
Consider your exits carefully. Fiberglass wins as long as you keep it out of your lungs.
https://en.wikipedia.org/wiki/The_Station_nightclub_fire
So you can see it takes a lot and this is why Earl has preferred pressure based damping.
I went this way some time back. After finding a place for 10 bags of rockwool and then going over the space with heavy drapes, I did begin to notice a difference in the bass. The thing is that it is possible to achieve about the same thing using multiple subs. (The higher frequency treatment is another issue, but you can still choose to keep your room live enough if you don't cover it with so much damping.)
Member turk 182 has had posting privileges in this thread removed, for continued unacceptable behavior.
I think that I should explain this comment since when I first read it I did not understand it.
Porous materials add absorption by a viscous drag of air motion through the material. Thus the more air motion the more effective it is. At a wall the air motion is zero and hence placing porous material on a wall is highly ineffective. However, the pressure is highest at a wall. Allowing this pressure to actually move the wall will allow for absorption through the actual motion of the wall. This is how I do sound absorption in my rooms and it appears to be very effective. This technique allows for high absorption at LFs and low absorption at HFs (the wall is too massive for HFs to move it,) which is precisely what I want to do.
Carpet flooring and acoustic tiling of the basement seem to have made a better situation out of a worse situation ie low ceilings. This is listening position, 1 meter away, one sub. 130inch wide walls, the sub mouth is ~32" from the nearest side wall. The dip just above 214hz should be due to internal, the carpet seems to be eating the null that was there before. Something tells me I am being lazy and could redesign the slot a little, fixing some other flaws as well. How hard is it to separate glued wood again? I forgot...hoped to never remember.
Edit... Shortening the slot causes a rise in GD in way that is not desirable, somehow the chosen port length after damping ends up with less problems than if I bury the woofer half way.... Guess I have merit to stick with what I have unless I figure out different.
Edit... Shortening the slot causes a rise in GD in way that is not desirable, somehow the chosen port length after damping ends up with less problems than if I bury the woofer half way.... Guess I have merit to stick with what I have unless I figure out different.
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This is the current (left) vs proposed half exposed woofer slot (right) Without enough space for damping material the response isn't repaired enough in the short slot. The deeper damping material fixes the resonance that remains at 100hz deep or shallow.
here is current slot with damping material and proposed slot without, The resonance at 100hz is not able to be nulled with damping in the short slot and EQ
Above in red is the shorter slot with proposed damping material vs current slot, Below is current slot after damping on the left and proposed slot on the right, in Red showing after EQing the GD peak out. Somehow the corrent slot wins. I can't add damping to the shorter slot without snuffing off the whole response, so its as if i actually have the slot that I desire and damping material is a necessary evil to get there.
here is current slot with damping material and proposed slot without, The resonance at 100hz is not able to be nulled with damping in the short slot and EQ
Above in red is the shorter slot with proposed damping material vs current slot, Below is current slot after damping on the left and proposed slot on the right, in Red showing after EQing the GD peak out. Somehow the corrent slot wins. I can't add damping to the shorter slot without snuffing off the whole response, so its as if i actually have the slot that I desire and damping material is a necessary evil to get there.
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OK I messed that one up, The path length is off 
The red is after eq and the proposed slots GD, with no Damping material
Thus, it would actually be an improvement?
The red is after eq and the proposed slots GD, with no Damping materialThus, it would actually be an improvement?
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Anyone happen to know how many Pascals an 18" should be able to handle? People say not to horn load a 15-18" because the pressure can destroy the diaphragm? Maybe this is only in a extreme situation?
This is possible within a similar size as my sub. The sim is just one 18"
This is possible within a similar size as my sub. The sim is just one 18"