Jesco, The model you use to calculate the absorption is from Allard and Champoux. Use a different model and you would have a different outcome. The model shows perpendicular reflection absorption. In real life materials absorb on all sides and all reflection angles. Low density reacts different at 45 degrees than high density. At Lacoustic we measured absorption for over 150 configurations and materials with an intensity probe. We measured from 20 Hz up. We found that using different densities makes a great difference. Right now we are able to make an absorber that effectively absorbs from 60 Hz to 20 kHz just using 3 different densities.
I thought it was a good point. I also use the simulations on this acoustic modelling page, and it is true that the results can vary depending on the model. However, no matter whether I use the Random incidence, change the Angle of incidence, or change the model, I do not get data that shows that high-density sound absorbers increase the low-frequency sound absorption more than low-density absorbers. (in base traps of 400mm or more, for example). If other simulation software or sites can provide such opposite results, could you please share the information?
I find it odd that in this video you don't mention the space behind the material as a factor. Your calculation only applies without any space behind the absorption. If one adds space behind the absorption then the calculation is very different and Higher density becomes more efficient again. So its more about figuring our how much space in ones room one is willing to give up (including the space behind the Absorption) and then working accordingly. I use 80kg/m3 material at 280mm thickness with equal space behind it (so total 560mm space used in room) and it is way more efficient than 560mm (without space behind) of 30kg/m3 density would be so it was cheaper to go with denser material where I had the space for it and less dense material where I didn't have the space. I hope this makes sense. Thank you so much for your videos, Ive learned and applied a tremendous amount because of the knowledge you shared.
Thank you for your videos focussing on the listening room instead of (selling) gear. Your guide is excellent because it summarizes the information about all common absorbers beyond bass treatment incl. placing to give a complete view.
Bruh I love you. I am in the planning phase of designing my next appartment where I will finally have a spare room that will become treated and I have been stuck in a rabbit hole the last 48h aimlessly researching what absorption materials are out tthere
If you try a porous absorber calculator, in the helmholz/multi-layer mode, you can see what it does. Basically high density over low density kind of "caps" the absorbtion at whatever the high density can absorb, seemingly. Real life result will likely be better. High density BEHIND low density will smoothen the curve a bit. But it's not really worth it.
thank you. excellent explanation. I've used your course materials and found them helpful. I'm in the middle of using 3 types of density materials building traps, mostly because I like to experiment. I have 5" dense, 5" very billowy non-dense fiber glass, and 4" safe and sound mineral wool. I'll try to keep you posted on what I've learned for my application=small mixing room (10'x 17' x 8'). Sorry I'm no good with metric conversions! Lastly, I got some MDF panels CNC cut 1/4" for the "bass traps" I'm building to attempt to tame some specific room nodes, and then will use a dbx driverack to "tune" the room in the end. I'm also thinking of using french cleats for mounting some of the diffusers and absorbers I'm building, so they'll be more modular. Lastly, using dampening neoprene and/or rubber wherever one surface touches another to minimize rumbling or buzzing sounds. Thanks Jesco! I've been working on this room for well over a year now and found your knowledge very helpful. Tschus!
Great explanation Thank you. I have made some triangular corner bass traps (due to limited space in the room to span corners with rectangular traps. I've stacked what is fairly low density slabs of insulation on top of one another to fill the trap. Unfortunately, the slabs eventually settled on one another to a point where the top of the trap is devoid of material. I packed more material in the top of the trap to fill the gap, but I'm assuming this is actually increasing the overall density of the trap (More material per cubic meter as the material settles)
Cool When I ran 703 models a while ago with that same website, a 4" panels spaced 2" off the wall was very similar to a 6" panel flush against the wall.
I was going to put a sheet of 4 lb rockwool that is ridgid on the outside to make sure it looks clean with the cloth, and backfill my superchunk with the least dense rockwool I can get (in Mexico). The absorbers/traps are going to be 90cm deep. Is this a bad idea? I really want to buy the course but I just don't have the budget since I am building out the studio solo DIY.
Would multi-density be better? i.e. Low density for the front of the panel, then higher density towards the middle, then lower density towards the back opening of the panel? That would be interesting to try.
I was about to ask the same thing. There's a video on UA-cam with Laurence Dicky of Vivid Audio. He uses exponentially tapered tubes to absorb the energy at the back of the drivers. He uses ordinary netting wool. He then makes a loop with some metal wire that he puts through from the back of the absorber, puts a pack of wool strings through the loop until centred and then pulls them back in. Because the tube is tapered and narrower towards the back, the wool packs more dense. I have to stress here that the absorbers are not absorbing low frequencies. Still, food for thought.
Hi Jesco. Could I get your advice on a concern I have? Feeling a bit lost for help... I just received 10 acoustic panels (2x4x3) for my home studio(just for mixing) and on closer inspection, I see that the fabric used to house the rockwool is 10oz canvas duck fabric. When I try to blow through it, it is very resistant to air passing through. From my research, this could be an issue with high end absorption as the sound waves will reflect too easily due to the tight fabric. At the risk of spending over 500$ to re-wrap them with a more porous material, I thought I'd ask your opinion as to wether you think that would be worth it or not. Based on your experience, do you believe the difference would be significant enough to embark on this tiresome project? Thanks
I'm guilty on this because of poor knowledge over the materials I was working with during the experiments I did back then. Here in my country flow resistivity is not displayed on rockwool manuals because institutions do not care about acoustics at all over here, I later learned that you have to request from factories this information and some of them doesn't even have this measured. There's huge variation in flow resistivity in rockwool of the same density and I didn't knew that until recently.
Hi Jesco, I don't want to contradict you, but isn't it easier to see the specification of the material, whether it is rock wool or fiberglass, if I look at the coefficient (alpha) of the material and see 125 Hz. The closer to 1 the better for low frequencies, obviously with the same thickness, like 1", 2", 4" or something like that.
Does anyone know how to get low density insulation in the UK? The commonly available product is Flexi / Sound Insulation Slab - 35kg/m³ - 14200(pa.s/m²) and RWA45 - 18100(pa.s/m²) which is way off the 5000 or 6000 pa.s/m2 I wanted (customer support gave me these values.
Hey Jesco, I have to take issue with your description of a 10-15% difference in LF that you describe at around 4:30. Saying that there is 10-15% difference is incorrect - what are you comparing to? At 50Hz the absorption coeffiecient of the yellow line is more than DOUBLE that of the blue. That is more than a 100% difference not 10-15%. At 800Hz you could say thet the blue one is at most 25% better. You know what they say "lies, damned lies and statistics"! I love your channel and know that you are a real help to people out there getting to grips with this stuff, but please don't misrepresent the mathematics in this way. And btw, I do understand what you were trying to say in percentage points where a coefficient of 1.0 is 100%, but the way you phrased it is massively misleading in trying to make your point.
Jesco, The model you use to calculate the absorption is from Allard and Champoux. Use a different model and you would have a different outcome. The model shows perpendicular reflection absorption. In real life materials absorb on all sides and all reflection angles. Low density reacts different at 45 degrees than high density.
At Lacoustic we measured absorption for over 150 configurations and materials with an intensity probe. We measured from 20 Hz up. We found that using different densities makes a great difference. Right now we are able to make an absorber that effectively absorbs from 60 Hz to 20 kHz just using 3 different densities.
I thought it was a good point.
I also use the simulations on this acoustic modelling page, and it is true that the results can vary depending on the model.
However, no matter whether I use the Random incidence, change the Angle of incidence, or change the model, I do not get data that shows that high-density sound absorbers increase the low-frequency sound absorption more than low-density absorbers. (in base traps of 400mm or more, for example).
If other simulation software or sites can provide such opposite results, could you please share the information?
I find it odd that in this video you don't mention the space behind the material as a factor. Your calculation only applies without any space behind the absorption. If one adds space behind the absorption then the calculation is very different and Higher density becomes more efficient again. So its more about figuring our how much space in ones room one is willing to give up (including the space behind the Absorption) and then working accordingly. I use 80kg/m3 material at 280mm thickness with equal space behind it (so total 560mm space used in room) and it is way more efficient than 560mm (without space behind) of 30kg/m3 density would be so it was cheaper to go with denser material where I had the space for it and less dense material where I didn't have the space. I hope this makes sense. Thank you so much for your videos, Ive learned and applied a tremendous amount because of the knowledge you shared.
Thank you for your videos focussing on the listening room instead of (selling) gear. Your guide is excellent because it summarizes the information about all common absorbers beyond bass treatment incl. placing to give a complete view.
Bruh I love you. I am in the planning phase of designing my next appartment where I will finally have a spare room that will become treated and I have been stuck in a rabbit hole the last 48h aimlessly researching what absorption materials are out tthere
What about with air gap behind them ? Mixed density traps ? I’d love to see those results
If you try a porous absorber calculator, in the helmholz/multi-layer mode, you can see what it does.
Basically high density over low density kind of "caps" the absorbtion at whatever the high density can absorb, seemingly. Real life result will likely be better.
High density BEHIND low density will smoothen the curve a bit. But it's not really worth it.
thank you. excellent explanation. I've used your course materials and found them helpful. I'm in the middle of using 3 types of density materials building traps, mostly because I like to experiment. I have 5" dense, 5" very billowy non-dense fiber glass, and 4" safe and sound mineral wool. I'll try to keep you posted on what I've learned for my application=small mixing room (10'x 17' x 8'). Sorry I'm no good with metric conversions! Lastly, I got some MDF panels CNC cut 1/4" for the "bass traps" I'm building to attempt to tame some specific room nodes, and then will use a dbx driverack to "tune" the room in the end. I'm also thinking of using french cleats for mounting some of the diffusers and absorbers I'm building, so they'll be more modular. Lastly, using dampening neoprene and/or rubber wherever one surface touches another to minimize rumbling or buzzing sounds. Thanks Jesco! I've been working on this room for well over a year now and found your knowledge very helpful. Tschus!
Great explanation Thank you. I have made some triangular corner bass traps (due to limited space in the room to span corners with rectangular traps. I've stacked what is fairly low density slabs of insulation on top of one another to fill the trap. Unfortunately, the slabs eventually settled on one another to a point where the top of the trap is devoid of material. I packed more material in the top of the trap to fill the gap, but I'm assuming this is actually increasing the overall density of the trap (More material per cubic meter as the material settles)
Literally about to buy my insulation and I have been racking my brain over this one for a while, thanks!
get caruso iso bond
Cool
When I ran 703 models a while ago with that same website, a 4" panels spaced 2" off the wall was very similar to a 6" panel flush against the wall.
I was going to put a sheet of 4 lb rockwool that is ridgid on the outside to make sure it looks clean with the cloth, and backfill my superchunk with the least dense rockwool I can get (in Mexico). The absorbers/traps are going to be 90cm deep. Is this a bad idea? I really want to buy the course but I just don't have the budget since I am building out the studio solo DIY.
Would multi-density be better? i.e. Low density for the front of the panel, then higher density towards the middle, then lower density towards the back opening of the panel? That would be interesting to try.
I was about to ask the same thing. There's a video on UA-cam with Laurence Dicky of Vivid Audio. He uses exponentially tapered tubes to absorb the energy at the back of the drivers. He uses ordinary netting wool. He then makes a loop with some metal wire that he puts through from the back of the absorber, puts a pack of wool strings through the loop until centred and then pulls them back in. Because the tube is tapered and narrower towards the back, the wool packs more dense.
I have to stress here that the absorbers are not absorbing low frequencies. Still, food for thought.
Always extremly usefull info! Thaks!
Hi Jesco. Could I get your advice on a concern I have? Feeling a bit lost for help... I just received 10 acoustic panels (2x4x3) for my home studio(just for mixing) and on closer inspection, I see that the fabric used to house the rockwool is 10oz canvas duck fabric. When I try to blow through it, it is very resistant to air passing through. From my research, this could be an issue with high end absorption as the sound waves will reflect too easily due to the tight fabric. At the risk of spending over 500$ to re-wrap them with a more porous material, I thought I'd ask your opinion as to wether you think that would be worth it or not. Based on your experience, do you believe the difference would be significant enough to embark on this tiresome project? Thanks
I believe 8 pound rock wool is very effective…especially if you build in a range limiter plate…and use air gap.
believing is useless
@@JohnSmith-pn2vl it’s what the large commercial trap companies are using in my country. USA. The independent lab tests enforce my beliefs.
Really good video thanks
Thank you for posting this video!
I'm guilty on this because of poor knowledge over the materials I was working with during the experiments I did back then. Here in my country flow resistivity is not displayed on rockwool manuals because institutions do not care about acoustics at all over here, I later learned that you have to request from factories this information and some of them doesn't even have this measured. There's huge variation in flow resistivity in rockwool of the same density and I didn't knew that until recently.
Hi Jesco, I don't want to contradict you, but isn't it easier to see the specification of the material, whether it is rock wool or fiberglass, if I look at the coefficient (alpha) of the material and see 125 Hz.
The closer to 1 the better for low frequencies, obviously with the same thickness, like 1", 2", 4" or something like that.
Does anyone know how to get low density insulation in the UK? The commonly available product is Flexi / Sound Insulation Slab - 35kg/m³ - 14200(pa.s/m²) and RWA45 - 18100(pa.s/m²) which is way off the 5000 or 6000 pa.s/m2 I wanted (customer support gave me these values.
How do you convert kg/m3 to Pa-s/m - for example RWA 45kg/m3 to Pa-s/m?
Gold !!
Exactly so,, 👍👍
Hey Jesco, I have to take issue with your description of a 10-15% difference in LF that you describe at around 4:30. Saying that there is 10-15% difference is incorrect - what are you comparing to? At 50Hz the absorption coeffiecient of the yellow line is more than DOUBLE that of the blue. That is more than a 100% difference not 10-15%. At 800Hz you could say thet the blue one is at most 25% better. You know what they say "lies, damned lies and statistics"! I love your channel and know that you are a real help to people out there getting to grips with this stuff, but please don't misrepresent the mathematics in this way. And btw, I do understand what you were trying to say in percentage points where a coefficient of 1.0 is 100%, but the way you phrased it is massively misleading in trying to make your point.