Using sand for enclosure dampening

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#21
Years ago I built a cabinet out of Sonotube concrete formers. It as a ten inch diameter inside a 12 inch diameter. The space in between was filled with play sand. It as the deadest cabinet I’ve ever seen. it weighed a ton and if you knocked on the side it had a dead thunk. The top of what looked like a periscope was made out of schedule 80 pvc pipe which is also very dead. I put a few deflector plates in the tube at 45 degree angles creating a labirinth path to break up standing waves. It was a very analytical speaker that did everything well but it lacked that something special that makes a speaker great to listen to. There are more than measurements to make a great speaker! The drivers were Scan Speak and they were bi amped but they had no life to them. It as an example exercise in theory that proved there is more than theory to a great speaker!
 
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#22
What you describe would be an almost perfect CLD cylinder. Because of its circular cross section, Sonotube has a lot of stiffness. An inch of sand between the two layers adds a lot of damping and A LOT OF MASS ! ...

Of course, a superb cabinet does not guarantee a great speaker. The on-off frequency response has to be excellent before things like cabinet stiffness and damping begin to make a difference.
 
#23
I like to build things, so that has meant that over the decades, I have built my share of cabinets for speakers. So few, in spite of claims, ever moved me. Sophisticated cabinets in some cases to open baffle designs. Many of them did so much right, but when it comes to bass, it can be its own challenge to get things 'right'. Too much, too little bump in the middle, you name it. Most of my cabinet builds are so very well braced and seemingly always heavy. Damping, (not dampening, like if you wet the bed) was not considered to be a major thing because of mass/bracing. I am sure that before it is all over, I will give this a try, especially since an additive to the sand can be quite effective or so they say. Still, I wonder about lead shot or another alternative.
 
#25
Yes, that makes sense to me. For so many of the possibilities mentioned, it would be great to have a recipe that describes everything from the coarseness of sand to any how much of other ingredients could be added, along with a given amount (to be researched for a given enclosure).
 
#26
maximax77 said:
Not sure though what that means when the sand-lamponite mixture is enclosed in speaker walls which seal the moisture level in.
Click to expand...

Apparently, moisture turns laponite into a thixotropic gel that becomes more fluid when agitated - just like when shaking a tomato sauce bottle.

Just as we would ensure the use of dry sand to fill a cabinet panel, I was considering the use of a dry sand-laponite mixture.

But perhaps I should go back to the drawing board! :cheerful:
 
#28
I only used dry “play sand” which is clean and sterilized. That way nothing living is in the mix and you won’t sprout weeds! It is a very fine grain sand they use in kids sand boxes. Don’t put in any additives because with a lot of vibration the different types of particles will separate by density, heavier on the bottom. You also want the particles to move and absorb the energy in addition to their mass damping. Damping has nothing to do with getting it wet! Don’t use any kind of goop with the sand, let it move. It’s easier than you’re making it!
 
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#31
Gilbert Briggs sand filled open baffle
BriggsBaffle.jpg
 
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#33
One thing to keep in mind when mixing grains/particles of different size together is the Brazil nut effect: https://www.scienceabc.com/pure-sci...unks-always-end-up-on-top-in-a-snack-jar.html

The Brazil nut effect is when larger grains will self sort to the top of a mixture of different sized grains when shaking it.

If the mixture will experience enough shaking over its lifetime for it to matter is another thing.
 
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#36
Ruark speakers, back in the 90's, had a compartment for inserting sand. Results were mixed.
Like the OP I've been curious to explore the best way to implement sand for damping but have given up.
Right now I'm building speaker cabinets designed to use the science of Single Degree of Freedom (SDF) to damp the speaker basket and return the energy back to the baffle to make it resonate in harmony with the cone. SDF science is used to make structures vibrate less violently during an earthquake and make aircraft and rockets vibrate less. My take in this costs peanuts to do but it's work-in-progress. Should anyone be interested I'm documenting it on my website [https://www.terrysweb.link/audio/loudspeaker].
 
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#38
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