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A comparison of the effectivity of various speaker damping materials

Any thoughts on damping that has a mass-loaded layer (such as one of the Sonic Barrier 3-layer materials) applied to the outside of a cabinet? Might it reduce transmission of sound from the cabinet walls?

I admit I am unclear on the propagation mechanisms of sound from cabinet wall vibration to the air, or I would try to figure this out.
It makes more sense to build the housing more stable from the start so that as little sound as possible is emitted through the walls.
Material that absorbs the sound waves by converting them into heat is also not so useful. On the one hand, you want the speaker to radiate all of its energy and damping/conversion never happens evenly across the entire frequency range. Such a material should only be used in a controlled manner and with a specific goal in mind.

A very ideal and inexpensive material for your purpose is soft fiberboard made of wood. Glued flat to the inside of the walls, they ensure that the walls can no longer vibrate as much because the different vibration properties of the materials hinder each other. The soft fiberboards have to be cut a little smaller so that they do not touch each other. They also disperse the sound waves, which is a good side effect.
 
If the goal is to reduce the panel vibrating, pretty sure inside vs outside mounting is unlikely to make much difference. What is the use case for outside? A padded speaker?



Ofc, the vibration source is the woofer, but propagation will depend on cabinet material(s), shape, dimensions, port tuning (if used) and how the driver is mounted.
Yes, I'm planning to use around 2" of sound absorption covered with acoustically transparent cloth on all cabinet surfaces to minimize diffraction. The sides and back will essentially look upholstered, saving a lot of cabinetry effort on appearance. I was thinking of Sonic Barrier for the front panel, which led me to think of using mass damping to reduce radiation of sound from the walls. I was not thinking in terms of mass-damping the motion of the walls, which is best dealt with by other means (as other posters have pointed out, thank you Roland68). The part I don't know is whether the transmission of sound from a vibrating surface (the wall) would be usefully reduced by having, from the inside out: the usual cabinet damping - MDF wall - absorbent foam or batting - a mass-loaded layer such as tar paper - more foam or batting - acoustically transparent cloth. If the massy layer is useless, I would leave it out and only use the outside treatment to reduce diffraction.

Early design stage here, but more than a thought experiment.
 
Yes, I'm planning to use around 2" of sound absorption covered with acoustically transparent cloth on all cabinet surfaces to minimize diffraction. The sides and back will essentially look upholstered, saving a lot of cabinetry effort on appearance. I was thinking of Sonic Barrier for the front panel, which led me to think of using mass damping to reduce radiation of sound from the walls. I was not thinking in terms of mass-damping the motion of the walls, which is best dealt with by other means (as other posters have pointed out, thank you Roland68). The part I don't know is whether the transmission of sound from a vibrating surface (the wall) would be usefully reduced by having, from the inside out: the usual cabinet damping - MDF wall - absorbent foam or batting - a mass-loaded layer such as tar paper - more foam or batting - acoustically transparent cloth. If the massy layer is useless, I would leave it out and only use the outside treatment to reduce diffraction.

Early design stage here, but more than a thought experiment.

My panel damping tests may be a while but am testing the Sonic Barrier denim without the panel damping layer, so might give you some idea. Would only expect a major benefit from panel damping if some aspect of the design needs it. Most of us do not have the benefit of major equipment and facilities to do vibration testing or simulation, so some will be proactive and slap added mass on the cabinet, I prefer to be more focused and test up front.

In my experience, the bigger need is to manage the energy from the woofer coupling to the cabinet. Unless you do force cancellation, this means focusing on the baffle mounting and/or the woofer motor assembly to help dampen. You see this in the better designs from respected manufacturers. That said, tried some CLD techniques on a subwoofer and seemed to cause more problems. Am not a mechanical engineer either so may have misapplied. Likely, its just not as simple as I hoped.
 
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I used to "mass load" dual layers of flat cement cast paver squares atop my big old Wharfedale speakers (sold last year) and believed it improved the sound. When considering damping as energy dissipation what is significant to consider is that there can arise assorted speaker cabinet resonant frequencies.

And the degree of damping ("loss coefficient" measurement) at different frequencies often does not measure the same for the selected damping material. What is desirable is a damping material which exhibits a quick response to (sonic) impact and oscillates relatively less while limiting transmission of force while any resonant frequencies are active.

When I mass loaded my speakers one layer of pavers probably gave me the best mechanical loss coefficient. However my speakers were large and at some resonant frequencies I think slightly moved the paver damper activating vibration in the cabinets; experimentally a double layer of mass loading (pavers) sounded better to me.
 
Ok, the new NoRez and 1 inch Sonic Barrier Acousta-Blue are on deck. Already am off to a bad start with the NoRez as it spews black particles all over as I cut it. Certainly not cutting as cleanly as the original. :( Wear a mask and be prepared to clean the sticky particles from the NoRez and your clothes. It appears that the new panel damping layer is more brittle and flakes off readily. My cotton t-shirt was not easy to clean…

Anyway, have to cut the denim yet, but need to go cut some lawn. The first round of testing came courtesy of about 2 weeks of rain. The first bit was a storm front and was fairly heavy, then we got a constant light rain via the remnants of Hurricane Helene. Not complaining as others got much worse.

Plan to be back in action tonight but have to take advantage of the first sunshine we have had in a while!

P.S. Realized had not shown the Sonic Barrier denim…

IMG_0821.jpeg

Heading claims it is 30 mm thick, but is more like 24ish (1 inch). Maybe you can fluff it in the dryer?
 
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Well, ran into a bit of snag as I started testing again. I installed the new NoRez and it did not seem to perform very well. I went back and rechecked the baseline and found the new test box is slightly different between 300-600 Hz. In a way, it is better as there is not as much port output as my earlier testing but would also mean that we would not be able to directly compare newer tests to older ones. As the 2 woofers have different run times, seemed likely that might be the difference, but after I swapped them, there was no change.

Am still drilling down on this difference between the two speakers, but aside from the removable back, not much else is obviously different.
 
Uh oh, did I order you a bad sample?o_O
 
Weddings are out of the way and spent some time trying to match the cabinets but was unable to nail down the difference. Have spent enough time on it, so am moving forward with the newer (better) cabinet. Here is the next major set of comparisons...

1728917838456.png


Baseline (no damping) as before in red. As posted earlier, it is a bit quieter in the 300-600 Hz range. Next in black is the new NoRez and does not match up as well to Sonic Barrier (SB) 1.25 as the original did. The other new addition SB Acousta-Blue (denim) is a bit better notably besting them all in the higher frequencies. Finally, in yellow is the SB 1.25 from the previous round just for continuity and to ensure equal conditions.

So, for knocking down the port resonance, SB 1.25 comes off on top for this comparo. Still like the denim as a more environmentally friendly approach. It is a bit thinner than the others tested in this post and a decent value, so will try adding another layer and report later.

My next plan is to move on to testing panel damping materials. Along with the SB 1.25 and new NoRez, I have Amazon butyl rubber and the SB lightweight vinyl. Before I move along, will entertain special requests to test other cabinet damping options. Any takers?


P.S. As I had about another side panel worth of the SB denim, I took out the back panel piece and curved the extra piece horizontally to add more damping to the sides. It improved slightly but still did not match the SB 1.25. To add more denim will involve tailoring it to fit better as otherwise space is limited.
 
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Do you have an easy way to test the denim (for example) in a higher velocity location than the cabinet wall? Somewhere near the middle of the cabinet, or some odd dimension away from the walls?
 
Do you have an easy way to test the denim (for example) in a higher velocity location than the cabinet wall? Somewhere near the middle of the cabinet, or some odd dimension away from the walls?

One obvious way I suppose would be to shorten or remove the port and insert the mic. The earlier testing is done right at the port opening. Ofc higher velocity could be simply achieved by increasing the voltage level too.

Would likely be helpful to describe the use case for the problem you want me to solve.
 
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One obvious way I suppose would be to shorten or remove the port and insert the mic. The earlier testing is done right at the port opening. Ofc higher velocity could be simply achieved by increasing the voltage level too.

Would likely be helpful to describe the use case for the problem you want me to solve.
Sorry I was not clear; my fault. I'm proposing the same mic position as your other tests but moving the damping material closer to the center of the cabinet. Since the air will be moving more there than it does close to the wall, the same amount of damping material may be more effective. In the past I've used a minimal amount of damping on the wall and some fluffed-up polyester off-center in a cabinet but never tested with and without, only adjusted the total amount for a reasonable impedance curve.
 
Sorry I was not clear; my fault. I'm proposing the same mic position as your other tests but moving the damping material closer to the center of the cabinet. Since the air will be moving more there than it does close to the wall, the same amount of damping material may be more effective. In the past I've used a minimal amount of damping on the wall and some fluffed-up polyester off-center in a cabinet but never tested with and without, only adjusted the total amount for a reasonable impedance curve.

Thanks. Can see this with Acousta-Stuf damping in post #74. Could do something comparable with the denim but is so dense, it would impede the internal airflow inside the cabinet. Check out the earlier post as I think it demonstrates your use case as am placing damping inside the box and not along the walls (until it starts to fill).
 
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Thanks. Can see this with Acousta-Stuf damping in post #74. Could do something comparable with the denim but is so dense, it would impede the internal airflow inside the cabinet. Check out the earlier post as I think it demonstrates your use case as am placing damping inside the box and not along the walls until it starts to fill.
Thanks, that indeed covers it. I can't tell how much to ascribe to placement vs. material, but looks better in lower frequencies and worse at higher.
 
Thanks, that indeed covers it. I can't tell how much to ascribe to placement vs. material, but looks better in lower frequencies and worse at higher.

Almost 200g of Acousta-Stuf is about as much as you could stuff inside the box and still be able to close it without difficulty. Since less than half as much was just as effective, there was no point in pushing past it. You are correct about the placement question, but if you compare it to the Dacron sheet (which did line the interior panels), the damping result was very comparable.
 
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While still may have some better panel damping property due to thicker asphalt layer, the new NoRez significantly underperformed in box damping compared to the original. This is not surprising when you work with the actual materials. Even visually, they are quite different…
IMG_0799.jpeg


Original is on the left and new NoRez on the right. The original foam layer is much more like Sonic Barrier than the new product and the top has a finish that is better at fending off dust and debris too.

P.S. was cleaning up the NoRez packaging and took a look at the GR invoice. @kyuu had kindly purchased and had it drop shipped to me. The shipping added another $15 so the total was $50 for the smallest quantity you can order.
 
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egg carton style foam maybe? So many variations in thickness and profile though, but also reportedly not that great. I would expect that the ideal material has the lightest energy-absorbing material- so a low density foam, with the greatest density of absorbing surfaces- so lots of small holes or densely packed very thin fibers. I wonder how the synthetic insulation in high end outdoor jackets would work, like Primaloft Gold or something like that, or maybe even actual goose down? Not a particularly cheap way to go but maybe not much more than Norez for the Primaloft:
 
egg carton style foam maybe? So many variations in thickness and profile though, but also reportedly not that great. I would expect that the ideal material has the lightest energy-absorbing material- so a low density foam, with the greatest density of absorbing surfaces- so lots of small holes or densely packed very thin fibers. I wonder how the synthetic insulation in high end outdoor jackets would work, like Primaloft Gold or something like that, or maybe even actual goose down? Not a particularly cheap way to go but maybe not much more than Norez for the Primaloft:

Have some egg crate foam, but it is rather old. Willing to test if someone supplies some newer stock. Anything speculative like Primaloft would need to be donated as well. Does Acousta-Stuf not fit the case already for a synthetic insulation? You can use it loosely or pack it more densely as I show in post #74.
 
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Some used the "magic eraser" as absorption for a 3" fullrange driver in a cone shaped enclosure.
"But even better than eggcrate foam are the melamine magic eraser pads (aka BASF Basotect). I would save those for lining the rear (including the side) walls facing the back of the driver. The will prevent any back reflection from getting back to the driver."
post 1971
 
Some used the "magic eraser" as absorption for a 3" fullrange driver in a cone shaped enclosure.
"But even better than eggcrate foam are the melamine magic eraser pads (aka BASF Basotect). I would save those for lining the rear (including the side) walls facing the back of the driver. The will prevent any back reflection from getting back to the driver."
post 1971

Thanks but already have discussed melamine in post #44. Has some nice properties but is not exceptional or cheap unless someone wants to glue magic erasers together (not me!). Maybe a decent answer for a small volume. Did not see any damping measurements on the thread you reference. Did I miss?
 
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