Man, so many materials have been tried for absorption/reflection in a speaker cabinet. It gets me to wondering about combinations where one material might be best in cabinet corners, another best port areas, still another in the general fill area. This in combination of cabinet material itself, and that also could be of more than one material.
I like the idea of melamine sponges - magic erasers. It is non-flammable according to matierals-info-org. The polyurethane foam most places sell produces phosgene gas & methychloride when burned. I was thinking jute batting, but it sheds particles that could get into the driver gap. Same with shredded denim.
Now if I could just find a couch stuffed with horsehair, I might not die of "smoke inhalation" in a house fire.
Now if I could just find a couch stuffed with horsehair, I might not die of "smoke inhalation" in a house fire.
Coming a bit late to the 'party', but FWIW the pioneers started with lambs wool to damp their compression drivers, but the times were full of bugs, rats, etc., that kept eating it, so developed stainless steel wool and still a fine choice today when not a lot is required for us budget minded.
Can't find a single example of austenitic (non-magnetic) steel wool available presently, or any reference of it ever being used in a production compression driver.
Iron is the primary material in stainless steel, it would be attracted to the magnetic gap, not a "budget minded proposition".
Mounting the woofer with motor sticking out would solve potential issues with motor magnetic interaction.
It could look something like this:
https://wilson-benesch.com/wp-conte...y-3zero-Standard-Finish-Black-Texture-web.jpg
It could look something like this:
https://wilson-benesch.com/wp-conte...y-3zero-Standard-Finish-Black-Texture-web.jpg
Is there any reason to believe that steel wool would provide better damping than the more conventional materials?
I saw it in some W.E. field coil horn drivers and IIRC some was recommended/used in some DIY modded kits which used Eminence drivers, but can't dredge up the kit's brand name ATM.
This is an interesting discussion,during Covid while I was designing and prototyping some small desktop full range boxes I had run out of polyfill and acoustmass and being the weekend could not place an order. So I was looking at some stuff in my attic and found some old klang & tong magazines where there was an article about making different constant layers damping, I decided to have some fun,I had lots of shredded denim,stainless steel mesh,copper mesh and silver mesh,from my wife’s yarn business where some yarns have these metals spun into the wool,yak merino etc to give them some metallic sheen which was the trend then,we have a few winding machines ( can’t do transformers unfortunately)
I put some of the mesh stuff in some old socks and stapled them into the boxes and they were actually damm good and each had their own unique effect,it’s very time consuming and all the materials come from 5 different vendors,I don’t know if and what effect they had on heat dispersion, I also did not measure the speakers as they would never get into any production.
we do have a few extra knitting machine and electric looms so I could make a few small patches with wool non magnetic stainless steel ,silk and other materials maybe 5 layers of 1/2 inch thick ,it will be expensive though and maybe will even measure it and see.
I will also make an audiophile version with cashmere silk and silver
I put some of the mesh stuff in some old socks and stapled them into the boxes and they were actually damm good and each had their own unique effect,it’s very time consuming and all the materials come from 5 different vendors,I don’t know if and what effect they had on heat dispersion, I also did not measure the speakers as they would never get into any production.
we do have a few extra knitting machine and electric looms so I could make a few small patches with wool non magnetic stainless steel ,silk and other materials maybe 5 layers of 1/2 inch thick ,it will be expensive though and maybe will even measure it and see.
I will also make an audiophile version with cashmere silk and silver
Friction, perhaps a little maybe, mostly not.
The bulk of the heat, rise in temperature, is caused by compression of the air (adiabatic heating) in the enclosure that then happens in reverse when the driver cone moves in the opposite direction. The heated air in turn heats the fiber of the stuffing. The added mass of the stuffing adsorbs more heat and acts like an increased volume enclosure. Fine fiber heats faster and gives the heat back to the air faster.
Study it in the MIT 1954 Leo L Beranek Acoustics text book.
Thanks DT
There is a difference between the eraser and the acoustic ones. The acoustic foam is very stiff.
Also, any material needs to have an air gap to work best.
Alpaca has air inside of the fiber. Anyone ever tried alpaca?
Any alpaca farm should have bags of the stuff since they can't sell the older animals fiber.
If you raise the pressure, the temperature of the air increases. But if you cool off the air to the same temperature, the pressure falls to the original value.
Any material with a heat capacity much higher than air could provide this function, but for it to be fully effective, thermal conduction from the air must not be the limiting factor. Hence wool or fiber of some sort with high surface area.
After writing that I wondered if activated charcoal could be used, and I quickly found this thread:
I think that basically, the high heat capacity of metal only gets you so far, it also needs to be fine enough to have enough surface area to absorb the heat from the air. So you end up with the ideal material being whichever has the highest porosity and heat capacity in balance with each other. Porosity being the one that is mainly difficult to find.
Any material with a heat capacity much higher than air could provide this function, but for it to be fully effective, thermal conduction from the air must not be the limiting factor. Hence wool or fiber of some sort with high surface area.
After writing that I wondered if activated charcoal could be used, and I quickly found this thread:
I think that basically, the high heat capacity of metal only gets you so far, it also needs to be fine enough to have enough surface area to absorb the heat from the air. So you end up with the ideal material being whichever has the highest porosity and heat capacity in balance with each other. Porosity being the one that is mainly difficult to find.
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A quick search and it would appear that aluminum wool exists. Which leads to just one question. Will androids dream of aluminum sheep?
https://www.amazon.com/Rogue-River-Tools-Aluminum-3-5oz/dp/B079Y3BMGT
https://www.amazon.com/Rogue-River-Tools-Aluminum-3-5oz/dp/B079Y3BMGT
Just thinking out loud, doesn't the air in a sealed box heat when the woofer goes into the box causing compressed air and therefore heat, and the air cools when the woofer cone moves out of the box causing low pressure and cooling the air? The net should be zero. My understanding of damping is it causes heat on both the outward and inward stroke of the woofer. The heat is caused by friction and movement of the fibers.
Also, fibrous damping absorbs high frequencies and converts the wave motion into heat which is a bit different than what is going on in the bass frequencies where the woofer is moving large volumes of air. The air + damping material in the woofer enclosure is now heavier than air alone due to the mass of the damping material. This theoretically increases the size of the box. I always wanted to try and make a subwoofer full of a heavier than air gas.
Back to the topic, a metal wool will have more mass and should offer great damping to increase the apparent size of an enclosure. However it may not work as effectively to damp higher frequencies for the same reason, it's too heavy and stiff. It won't sympathetically vibrate with the air. Easy enough to experiment with.
I would try an experiment where I'd fill a box with various damping materials and stick my ear over the hole and listen. I might try a Leia hairdoo of steel wool and (like Dr. Ray Stantz) see what I can hear.
Sounds like a heat flow problem to me.
Rate of adsorbing and returning heat. Total heat exchanged considering things like Specific Heat, Mass and surface area.
Could be done like Linkwitz did, measure the impulse response inside the enclosure with a in box microphone. Then stuff to minimize the internal reflections and to minimize the sound reflecting back out through driver cone.
Thanks DT
Rate of adsorbing and returning heat. Total heat exchanged considering things like Specific Heat, Mass and surface area.
Could be done like Linkwitz did, measure the impulse response inside the enclosure with a in box microphone. Then stuff to minimize the internal reflections and to minimize the sound reflecting back out through driver cone.
Thanks DT
For showpiece acrylic cabinets, this might be considered. Doesn't really matter if it does anything when you are focusing on a visual, right? I think that particular enhancement might lead me sell my Anaconda sized speaker cables and concentrate on the boxes.
Who's in? I don't need a hundred feet of it and I can use the rest for scrubbing the pots my honey forgot about on the stove.
Who's in? I don't need a hundred feet of it and I can use the rest for scrubbing the pots my honey forgot about on the stove.
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Along with the boring and rather standard rockwool and animal wool,
I like Asian jello (Agar jelly) in 2 litre containers suspended from the top of the cabinet on strings. Sometimes, tied to the bottom as well.
Combined with lead sheet, with or without holes punched in them, also strung from the top of the cabinet, but not pinned to the base.
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Lead and copper. hmmm will be going to the gun range on Friday. I'll think about it.