Best Material for Filling Hollow Rack Legs?

Ron Resnick

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Jan 25, 2015
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#1
The legs of my current stand are three inches square. Many years ago I filled them up with sand to maximize damping and to minimize any resonance in the legs.

But sand is kind of messy to work with. What are other options for filling up hollow legs for damping purposes?

What about solid stainless steel ball bearings?

What about little balls of lead?
 

bonzo75

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Feb 26, 2014
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#3
The balls might vibrate against each other inside the legs causing ringing sounds.
 
Jan 29, 2012
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#4
I bought led shot from Amazon. I could actually hear the difference immediately, unlike a lot of my tweaks.
 

Folsom

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Oct 26, 2015
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#5
Sand does next to nothing unless the top is floating on it.

The only thing you are really doing is increasing the weight by filling them internally. Vibrations have little to no reason to transfer to whatever is inside the legs because they will simply travel through the stiffer directly coupled path, first. So basically the weight is lowering the resonant frequency that is coming up into it from below, but nothing like a solid stand would. At best filling them internally cuts down internal standing waves; but those waves do precisely nothing to begin with.
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
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#6
The legs of my current stand are three inches square. Many years ago I filled them up with sand to maximize damping and to minimize any resonance in the legs.

But sand mis kind of messy to work with. What are other options for filling up hollow legs for damping purposes?

What about solid stainless steel ball bearings?

What about little balls of lead?
go to a gun store and purchase steel shot. cheap. but very heavy.

but be open to any possible result. in my case I filled my GPA Monaco rack legs with steel shot, and it killed (over damped) the sound sitting on my concrete floor. lowered the noise. but no action or pace. if I had a suspended wood floor, it might have dampened it perfectly. there is never any completely predictable result when adding mass or something that takes the life out of a rack. so have a plan to remove it if you need to.

to get rid of my steel shot I gave it to a fellow audiophile. not sure what he did with it.
 

Elliot G.

Industry Expert
Jul 22, 2010
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Fort Lauderdale, Florida
#7
The legs of my current stand are three inches square. Many years ago I filled them up with sand to maximize damping and to minimize any resonance in the legs.

But sand mis kind of messy to work with. What are other options for filling up hollow legs for damping purposes?

What about solid stainless steel ball bearings?

What about little balls of lead?
Sand is a great insulator and so is foam that you can blow in.
Are you trying to stop it from ringing or add mass?
They are of course different choices. You can take shot and sand for example
 

Ron Resnick

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Jan 25, 2015
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#8
Mike, thank you for that report. Do you think the same concern applies if the rack in question is going to hold electronics, and not a turntable?
 

Ron Resnick

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Jan 25, 2015
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#9
Elliot, I mainly want to prevent ringing.

The legs of my planned custom Herzan stand are three inch square box legs. David is not keen on Herzan stands for audio purposes so I am seeing how I can make the legs less resonant.
 
May 30, 2010
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Portugal
#11
Elliot, I mainly want to prevent ringing.

The legs of my planned custom Herzan stand are three inch square box legs. David is not keen on Herzan stands for audio purposes so I am seeing how I can make the legs less resonant.
Unfortunately as Mike said it is a try and listen job. It is similar to speaker stands - it must be tuned, some manufacturers mix materials. Some people are against fully filing the legs up to the top. The problem is that no stand manufacturer will write his secret recipe in an audio forum, but probably David will suggest pouring melted stainless steel inside! :)
 

Ron Resnick

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Jan 25, 2015
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#12
But sand is messy. In your opinion will stainless steel ball bearings or shot also dampen ringing?
 

Elliot G.

Industry Expert
Jul 22, 2010
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Fort Lauderdale, Florida
#14
But sand is messy. In your opinion will stainless steel ball bearings or shot also dampen ringing?
Shot is usually added to add mass. I am sure filling the tube will help prevent it from ringing . Metal however does transmit sound sand does not!
 

Mike Lavigne

Member Sponsor & WBF Founding Member
Apr 25, 2010
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#15
Unfortunately as Mike said it is a try and listen job. It is similar to speaker stands - it must be tuned, some manufacturers mix materials. Some people are against fully filing the legs up to the top. The problem is that no stand manufacturer will write his secret recipe in an audio forum, but probably David will suggest pouring melted stainless steel inside! :)
no, no, no. David will spec depleted uranium.:eek::eek::eek:
 
Jul 22, 2010
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#16
I used clay based kitty litter in my speaker stands on recommendation of the stand manufacturer. I think they recommend polymer pellets now.
 
Last edited:

Folsom

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Oct 26, 2015
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#17
I used clay based kitty litter in my speaker stands on recommendation of the stand manufacturer. I think the recommend polymer pellets now.
Clay makes more sense than sand.

The biggest problem you have is that coupling is absolutely pathetic. That's why none of this truly does a lot. Most people add something and then assume it's 1000% magically better, when in reality it's maybe slightly better, if at all, depending on the thickness. Sand for example will help thin walled stuff that tends to move because it's putting pressure onto the wall. With thick walls it does approximately nothing for traveling waves, and only lowers resonances coming up from the weight applied to the bottom.

Here's a thought experiment. Put 20lbs of sand on top of a very flexy piece of of metal. Now hit the metal with a hammer perfectly straight on, perfectly flat. The sand will make the metal contort a little and nothing will move. Now put a 1/2" piece of aluminum panel down and 20lbs of sand sitting on top of it. Hit it with a hammer. The whole thing moves EASILY, as if there's no sand there. The amount of sand (force from gravity pushing it out/down) to stop a solid wall from moving is proportional to the mass of the wall. The proportion necessary to stop the thicker wall from moving FAR exceeds how much you can stuff into the legs of a rack that are beyond flimsy thin. SO the weight alone of the sand is the only acting force, and it isn't a very good one.

If you fill the legs with steel shot, you increase the proportions of weight to stiffness significantly. Suddenly it begins to couple better. The extra weight reduces the resonance. So even while the steel shot can transfer more energy, by doing so it'll reduce the frequency of that energy greatly. There is a loss of energy as it is harder to move more mass. The point being that it's wrong to fear the steel shot because it "could also ring". That is unless the idea of the world's tiniest bell ringing keeps you up at night, but huge audio gear racks ringing does not.

Now let's look back at the example of sand and thin material. If you had an unpoppable balloon filled with 400lbs of sand that you put your turntable on top of, it'd work great. The balloon would be too compliant and therefor transfer basically no energy itself, and the sand would dissipate energy very quickly. How can you do that without a beanbag like style rack? Easy. You simply have to remove the coupling between the shelf and the stand itself. The shelf has to sit only coupling to the sand within the stand. If that is true then all the energy must transfer across the sand, which dissipates energy very quickly. I will however note that sand's low mass does not make it the best for all frequencies. I have my table on top of a box filled with sand. The top of the box is floating on the sand. It works well for small vibrations but does literally nothing for a big one like someone jumping up and down on the floor next to it (my floor is too weak, and I find it easy enough not to jump up and down over crawling the long distance under the house to strengthen it).

Anyways... I hope that helps some. Maybe if we had some pictures of the rack parts we could come up with a solution to improve it? Floating on clay kitty litter? That would have damping.

BTW I think over damping killing the sound in a stand simply means something else needs adjusted. I don't think added information from vibrations getting into the TT is the ultimate way to achieve excitement in your stereo. But I can't argue with an unwillingness to pursue the effort when you're happy with what you got, without too much damping. Some things in stereos become a full-time job we can't all afford to have on top of life..
 

Folsom

VIP/Donor
Oct 26, 2015
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Eastern WA
#18
Metal however does transmit sound sand does not!
That depends on the frequency and amplitude. Amplitude is directly affected by mass.

If you strike a hammer on a leg stand filled with sand, that has a stiff wall, no the sand won't transfer any sound. But the energy will just continue through the leg, mostly as if there was nothing in the leg, going around to the other side. If you did it at the base, the sand would do more, but not a lot. The coupling just isn't good enough. If you use something with more mass that can make gravity couple it better (press against the walls), then you'll send more energy into the filling of the leg.
 

ddk

Industry Expert
May 19, 2013
3,819
318
83
Utah
#19
The legs of my current stand are three inches square. Many years ago I filled them up with sand to maximize damping and to minimize any resonance in the legs.

But sand is kind of messy to work with. What are other options for filling up hollow legs for damping purposes?

What about solid stainless steel ball bearings?

What about little balls of lead?
Lava! ;)

is this an active stand?

david
 
Jun 23, 2015
78
0
6
Brisbane
#20
The legs of my current stand are three inches square. Many years ago I filled them up with sand to maximize damping and to minimize any resonance in the legs.

But sand mis kind of messy to work with. What are other options for filling up hollow legs for damping purposes?

What about solid stainless steel ball bearings?

What about little balls of lead?
Ron - I have used lead shot mixed with fine glass blasting beads ( for sand blasting ) - the idea is the glass is spherical and it fills the gaps and does not lock together like sand or shot - seemed to work

if I was doing it again I would pour in a viscous product like vinyl flooring adhesive and add lead shot - tamping it down as you go to get plenty of mass and fill the voids

you could then say you had randomly distributed mass damping particles in a lossy polymer matrix

a bit hard to reverse but it would work at damping ... something

cheers

Phil
 

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