I don't know how the prices of the two absorption materials compare, but to me the Sonic Barrier looks more effective than denim. It has almost the same effect as denim insulation at almost half the thickness. Also, looking at the box panel resonance at cca 700Hz it can be seen that the peaks shifted cca 50Hz lower with Sonic Barrier maybe suggesting that it has greater effect on making the box virtually larger (if the effect is not from shifting the panel resonance more by its greater mass touching the panel) It's the same with other peaks. It would be very interesting to see comparation of the two materials at equal thickness.
Yes the Sonic Barrier is really good. Its high price deters people from using it, and I don't know that it is available outside the US. There is also a multi-density version that is intended to damp wall vibration.
Yes, but ultimately the deciding factors are cost, ease of installation, availability, effectiveness, etc. Doubling up on the Sonic Barrier could be very expensive. With the same amount of money you might be able to add more denim insulation. So, as you spend more and more, is there a point where SB gets to be more effective than the denim at any price point? Maybe it is useful for niche applications where you need the absolute best absorption/damping within a small volume?
I think that’s exactly what it is, especially since the material is adhered to the panels with PSA
A couple years ago there was a threaded started at avsforum that encouraged me to start this project. Here are some selected posts that lay out the argument well:
Once I move on to CLD construction, I need recommendations on the adhesive. I've read silicone is not very good at dampening vibration, but would like cheap, common caulk to use as a baseline. To step it up a notch, the newer MS polymer adhesives are apparently the way to go:
Amazon.com: WEICON 13305310 Flex 310 M Classic MS-Polymer 310 ml Grey Elastic 1-Component Adhesive: Home Improvement
Amazon.com: Red Devil 098712 0987 RD3000 Advanced All Purpose, 9 oz, Clear, Case of 12 MS Polymer Sealant: Home Improvement
Rayt 1881-52 Sprint Polymer: MS Hybrid Polymer - Adhesive + Sealant. All in 1: Paste, Seal and Repair Glass, Metals, Wood, PVC, Porcelain, concrete, Transparent, 290ml - - Amazon.com
Amazon.com: Deka Dekasyl MS-2, White: Automotive
WEICON Speed-Flex MS-Polymer 310ml White Adhesive and Sealant - - Amazon.com
Amazon.com: WEICON 13305310 Flex 310 M Classic MS-Polymer 310 ml Grey Elastic 1-Component Adhesive: Home Improvement
Amazon.com: Red Devil 098712 0987 RD3000 Advanced All Purpose, 9 oz, Clear, Case of 12 MS Polymer Sealant: Home Improvement
Rayt 1881-52 Sprint Polymer: MS Hybrid Polymer - Adhesive + Sealant. All in 1: Paste, Seal and Repair Glass, Metals, Wood, PVC, Porcelain, concrete, Transparent, 290ml - - Amazon.com
Amazon.com: Deka Dekasyl MS-2, White: Automotive
WEICON Speed-Flex MS-Polymer 310ml White Adhesive and Sealant - - Amazon.com
Meniscus bonded dacron batting 1 layer
2 layers
Not great, but the reason I wanted to test this dacron batting was that it is very popular with the transmission line designers, who use it to stuff the first half of the line behind the driver, and this batting provides a consistent density. Here I stuffed the box:
polyester pillow stuffing @ 1/3 of a pillow
2 layers
Not great, but the reason I wanted to test this dacron batting was that it is very popular with the transmission line designers, who use it to stuff the first half of the line behind the driver, and this batting provides a consistent density. Here I stuffed the box:
polyester pillow stuffing @ 1/3 of a pillow
Okay- this confirms my wool thoughts of the past. I was able to source 100% wool-batting from one of the material-for-quilting suppliers, and was surprised at the benefit.
I had a pound of Acousti-Stuf in the rear of the box, and a 'twinky' (couple zip-ties for keepers) of a denser stuffing surrounded by the wool-batting (2 layers) operating vertically in the box. This hits the central resonance line with denser material, allowing the natural damping of wool, and the thicker layer of fill for the rear reflection reduction. Granted, I also had mass-loads of sand to either side of the front baffle and hindered the initial oscillation from the get go. The combination worked wonders. I would think the Ultratouch would work as the central damping, but I used the Natur-Fil 100% shredded bamboo-to-rayon fiber fill; which is NLA to my knowledge. I love that stuff! It has the consistency of natural cotton, but a bit denser.
Later,
Wolf
I had a pound of Acousti-Stuf in the rear of the box, and a 'twinky' (couple zip-ties for keepers) of a denser stuffing surrounded by the wool-batting (2 layers) operating vertically in the box. This hits the central resonance line with denser material, allowing the natural damping of wool, and the thicker layer of fill for the rear reflection reduction. Granted, I also had mass-loads of sand to either side of the front baffle and hindered the initial oscillation from the get go. The combination worked wonders. I would think the Ultratouch would work as the central damping, but I used the Natur-Fil 100% shredded bamboo-to-rayon fiber fill; which is NLA to my knowledge. I love that stuff! It has the consistency of natural cotton, but a bit denser.
Later,
Wolf
CLD adhesive options
I've been doing some research on this topic and wanted to share some additional brand-names I've read about in other threads:
Smooth-On manufactures a variety of Polyurethane products for mold-making that appear to meet the specifications of both an adhesive and damping material for CLD, it can be purchased at https://www.reynIoldsam.com/product-category/urethane-rubber/https://www.smooth-on.com/products/vytaflex-40/
Vytaflex mixed in combination with Ure-Fil 15 may provide the combination of elasticity and damping needed for an effective CLD material.
Innovative Polymers Innothane IE40A is another product with similar properties.
Both of the above products are probably more expensive and difficult to source, but perhaps higher performing than a caulk-type or sealant. Ultimately your tests may help establish whether the difference is worth the price for our intended application.
Sikaflex+ Construction sealant is another Polyurethane-based caulk, and seems to retain good elasticity over the life of its application, but as with most caulks, we are at the mercy of the manufacturer's secret sauce regarding the effectiveness of its damping properties when used as CLD material.
Lastly I have a few construction-related thoughts about your CLD tests. One question is about the degree of freedom necessary for the damping to be optimally effective. If the constraining is done by sandwiching a viscoelastic material between two stiffer materials, it seems to me one of the two stiffer materials should be thought of as "Structural" and the other allowed to flex more, especially at the edges (the Constraining layer), in order to maximize the damping of the assembly through shearing action. In a composite panel, this shearing action is the opposing forces on two outer surfaces, mediated by the viscoelastic material binding and damping them. (and thus the constrainig layer should not be attached to another panel at the edges). I've been thinking that a 1/2" or 3/4" "structural" Plywod or MDF sheet bonded to 1/8" Hardboard "constraining" layer on the inside (that is not glued at the corners, but perhaps separated by 1/8" CLD joint there too) should out-damp vibration when compared with a more traditional construction approach that 1) uses two equal materials for the stiffness layers and 2) attaches all edges of both structural and constraining layers at the corners.
My second thought is about baffle construction and driver attachment. I have read that of all speaker panels, the front baffle benefits most from CLD since it is directly attached to the drivers that are the source of cabinet vibration. To that end, there has been discussion in other threads about how to optimally attach drivers on-to a CLD baffle. (Attaching through all layers might reduce damping action, but attaching to a single stiff layer only may not provide enough stiffness for a woofer). My though was to double-up the structural layer (with a plywood or mdf ring) at the woofer attachment but still keep the constraining layer somewhat separate from that (1/8" away, but also using CLD at the edge) so that its damping action would be effective at all points of the baffle except for driver attachment and panel edges.
My third thought is (none of these are original to me by the way) the idea of attaching split, but overlapping braces connected via CLD methods at the overlap zone to both stiffen and dampen vibration in speaker panels. The point that intrigues me about this is that two opposing panels would tend to have different vibration modes (perhaps even cancelling each other) and the addition of a CLD brace may dampen vibration even further beyond what a CLD panel may do by itself (for example, if we find that CLD acts best at higher frequencies, the brace may complement that and help reduce vibration at lower frequencies).
These are some of the things I've been considering, so I'm excited to see your results, Six.
I've been doing some research on this topic and wanted to share some additional brand-names I've read about in other threads:
Smooth-On manufactures a variety of Polyurethane products for mold-making that appear to meet the specifications of both an adhesive and damping material for CLD, it can be purchased at https://www.reynIoldsam.com/product-category/urethane-rubber/https://www.smooth-on.com/products/vytaflex-40/
Vytaflex mixed in combination with Ure-Fil 15 may provide the combination of elasticity and damping needed for an effective CLD material.
Innovative Polymers Innothane IE40A is another product with similar properties.
Both of the above products are probably more expensive and difficult to source, but perhaps higher performing than a caulk-type or sealant. Ultimately your tests may help establish whether the difference is worth the price for our intended application.
Sikaflex+ Construction sealant is another Polyurethane-based caulk, and seems to retain good elasticity over the life of its application, but as with most caulks, we are at the mercy of the manufacturer's secret sauce regarding the effectiveness of its damping properties when used as CLD material.
Lastly I have a few construction-related thoughts about your CLD tests. One question is about the degree of freedom necessary for the damping to be optimally effective. If the constraining is done by sandwiching a viscoelastic material between two stiffer materials, it seems to me one of the two stiffer materials should be thought of as "Structural" and the other allowed to flex more, especially at the edges (the Constraining layer), in order to maximize the damping of the assembly through shearing action. In a composite panel, this shearing action is the opposing forces on two outer surfaces, mediated by the viscoelastic material binding and damping them. (and thus the constrainig layer should not be attached to another panel at the edges). I've been thinking that a 1/2" or 3/4" "structural" Plywod or MDF sheet bonded to 1/8" Hardboard "constraining" layer on the inside (that is not glued at the corners, but perhaps separated by 1/8" CLD joint there too) should out-damp vibration when compared with a more traditional construction approach that 1) uses two equal materials for the stiffness layers and 2) attaches all edges of both structural and constraining layers at the corners.
My second thought is about baffle construction and driver attachment. I have read that of all speaker panels, the front baffle benefits most from CLD since it is directly attached to the drivers that are the source of cabinet vibration. To that end, there has been discussion in other threads about how to optimally attach drivers on-to a CLD baffle. (Attaching through all layers might reduce damping action, but attaching to a single stiff layer only may not provide enough stiffness for a woofer). My though was to double-up the structural layer (with a plywood or mdf ring) at the woofer attachment but still keep the constraining layer somewhat separate from that (1/8" away, but also using CLD at the edge) so that its damping action would be effective at all points of the baffle except for driver attachment and panel edges.
My third thought is (none of these are original to me by the way) the idea of attaching split, but overlapping braces connected via CLD methods at the overlap zone to both stiffen and dampen vibration in speaker panels. The point that intrigues me about this is that two opposing panels would tend to have different vibration modes (perhaps even cancelling each other) and the addition of a CLD brace may dampen vibration even further beyond what a CLD panel may do by itself (for example, if we find that CLD acts best at higher frequencies, the brace may complement that and help reduce vibration at lower frequencies).
These are some of the things I've been considering, so I'm excited to see your results, Six.
I have tried a shore 60A polyurethane rubber and it worked great in a quick test using some ikea wood sticks toy thing. But that was in a simple knock test.
I glued two sticks together with straight wood glue titebond 3 as reference.
And the rubber with different thickness. Wood glue still have a high Q resonance while the rubber clearly dampens it.
https://www.smooth-on.com/tb/files/ECON_60_TB.pdf
That’s a similar product as I tried.
It also works as an adhesive as long as the surface is clean.
I glued two sticks together with straight wood glue titebond 3 as reference.
And the rubber with different thickness. Wood glue still have a high Q resonance while the rubber clearly dampens it.
https://www.smooth-on.com/tb/files/ECON_60_TB.pdf
That’s a similar product as I tried.
It also works as an adhesive as long as the surface is clean.
It is open cell.
I found someone selling it for accoustics that had a graph:
Melamine Acoustic Foam | Open Cell Melamine Foam
"Melamine is a flexible, open cell foam made from melamine resin, a thermoset polymer. ... Its characteristic feature is its three-dimensional network structure consisting of slender and thus easily shaped webs and provides abrasiveness when the material is used as a cleaner."
The CLD bracing approach that Sixto mentions sounds very similar to what Earl Geddes has used in his speakers. I have been intrigued by that approach and would love to see a comparison test against rigid bracing. Thanks for doing these tests Augerpro. As others have mentioned, if you set up a link for donations I would love to chip in.
I'm ordering some tomorrow for testing. It would be great if we could find something as good as the denim, but without the shedding of fine fibers.